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NEUROMUSCULAR DISORDERS

Congenital Myasthenic Syndrome in Hyderabad: The Genetic Neuromuscular Junction Disorder Where the Treatment Depends Entirely on Which Gene Is Mutated

Expert genetic diagnosis and gene-specific treatment for CMS at KIMS Neuroscience, Secunderabad, Hyderabad — informed by the 156-patient Indian CMS cohort (Brain 2024).

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CMS is a group of rare GENETIC disorders — NOT autoimmune — caused by mutations in genes encoding proteins at the neuromuscular junction (NMJ). Unlike Myasthenia Gravis (caused by antibodies attacking the NMJ), CMS is caused by inherited gene mutations that structurally or functionally impair NMJ neurotransmission. 40 different genes have been reported to cause CMS, affecting presynaptic, synaptic, and postsynaptic components of the NMJ. CMS presents from birth or early childhood with fatigable muscle weakness (worse with exertion, better with rest), ptosis, and ophthalmoparesis. AChR antibodies are NEGATIVE (distinguishing from autoimmune MG). CMS does not respond to immunosuppression. Treatment depends entirely on which gene is mutated: pyridostigmine (AChE inhibitor) is effective for CHRNE, RAPSN mutations but is CONTRAINDICATED in COLQ mutations (worsens by preventing acetylcholine clearance); salbutamol (beta-2 agonist) is effective for DOK7, MUSK, AGRN mutations. The wrong drug for the wrong genotype causes clinical harm, not benefit. In India (Brain 2024 cohort, 156 patients): CHRNE most common (39.4%), DOK7 14.4%, DPAGT1 9.8%. Eight variants geographically specific to the Indian subcontinent. Autosomal recessive inheritance in most forms — elevated frequency in South India from consanguinity.

CMS vs MG — the distinction that determines treatment: Myasthenia Gravis (MG): AUTOIMMUNE, caused by antibodies (AChR or MuSK) attacking the NMJ. Responds to immunosuppression (steroids, azathioprine, mycophenolate, rituximab). AChR or MuSK antibodies POSITIVE in most cases. Onset typically in adulthood. Congenital Myasthenic Syndrome (CMS): GENETIC, caused by inherited gene mutations. Does NOT respond to immunosuppression. AChR antibodies NEGATIVE (as expected — CMS is not autoimmune). Onset from birth or early childhood. CMS and juvenile autoimmune MG can appear clinically identical — the antibody panel and, crucially, the gene panel separate them.
CHRNE most common in India — the Brain 2024 cohort: The largest genetic characterisation of CMS from India was published in Brain 2024 — 156 patients from 141 families. Gene frequency in the Indian cohort: CHRNE 39.4% (epsilon subunit of the acetylcholine receptor — significantly more common in India than in European cohorts), DOK7 14.4%, DPAGT1 9.8%, GFPT1 7.6%, MUSK 6.1%. Novel genes MACF1 and TEFM were identified for the first time globally in this cohort. Eight variants were found to be geographically specific to the Indian subcontinent, reflecting founder effects in the Indian genetic background. This cohort defines the mutation spectrum that KIMS uses to prioritise gene panel interrogation.
Pyridostigmine in COLQ CMS — the drug that worsens the disease: Pyridostigmine is the standard first-line drug given to children with suspected MG or CMS (it inhibits acetylcholinesterase, the enzyme that breaks down acetylcholine at the NMJ). It works well for CHRNE, RAPSN, and other CMS subtypes where the problem is reduced acetylcholine signalling. But in COLQ mutations — where COLQ encodes the enzyme that anchors acetylcholinesterase to the NMJ — pyridostigmine dramatically worsens the condition. The COLQ defect already reduces acetylcholinesterase at the NMJ; pyridostigmine further inhibits the remaining enzyme, preventing acetylcholine clearance, producing sustained depolarisation of the postsynaptic membrane (depolarisation block), and worsening the weakness. A child with COLQ CMS given pyridostigmine will deteriorate. The gene panel result is required before prescribing.
Salbutamol for DOK7, MUSK, and AGRN mutations: Salbutamol (albuterol), the beta-2 agonist widely used in India as a bronchodilator for asthma, has emerged as an effective treatment for CMS subtypes caused by DOK7, MUSK, and AGRN gene mutations. These CMS genes encode proteins involved in NMJ development and structural maintenance (rather than direct neurotransmission). The beta-2 agonist mechanism: salbutamol upregulates agrin expression and promotes NMJ structural stabilisation, improving neuromuscular transmission. DOK7 CMS (the second most common gene in India at 14.4%) specifically responds to salbutamol (and ephedrine) but does NOT typically respond well to pyridostigmine.
Consanguinity and glycosylation-gene CMS — South India specific: The Brain 2024 Indian cohort shows a higher frequency of glycosylation-gene CMS subtypes (DPAGT1, GFPT1, GMPPB) compared to European cohorts. These genes encode enzymes in the N-glycosylation pathway; their recessive mutations require two mutated copies. Consanguineous marriage (significantly more common in Telangana and AP) increases the probability of both copies being mutated. Children from first-cousin marriages presenting with fatigable weakness from infancy require glycosylation-gene CMS in the differential. The KIMS CMS gene panel covers all 40 known CMS genes including the glycosylation genes.
Neonatal and early-childhood CMS — distinguishing features: CMS presenting in neonates: generalised hypotonia, feeding difficulty, respiratory distress, and fatigable weakness in a neonate with NEGATIVE maternal MG antibodies (if antibodies were positive: neonatal autoimmune myasthenia). CMS presenting in early childhood: ptosis (worse in the evening, better in the morning), ophthalmoparesis, and fatigable proximal weakness exacerbated by activity. The repetitive nerve stimulation (RNS) test in CMS shows a decremental response at low-frequency stimulation (3 Hz), similar to acquired MG. Unlike MG, the response to immunosuppression is absent. The antibody panel (AChR and MuSK) is negative. The CMS gene panel provides the specific diagnosis.
The wrong drug harms — the clinical imperative for genetic diagnosis: The most important principle in CMS management: the treatment is completely gene-specific, and the wrong drug for the wrong genotype does not simply fail to help — it actively worsens the condition. Pyridostigmine for COLQ: worsens. Drugs with anti-AChE activity for slow-channel syndrome: may worsen. Pyridostigmine for some glycosylation-defect CMS: limited or no benefit. At KIMS, CMS management does not proceed to treatment until the specific gene is identified. If the gene panel result is delayed, the safest interim approach is supportive management without pharmacological NMJ manipulation until the genetic result directs treatment.

About This Condition

Congenital Myasthenic Syndrome at a Glance

The essential concepts that determine how CMS is recognised, inherited, and — crucially — safely treated.

What it is

A group of rare genetic disorders caused by mutations in genes encoding proteins at the neuromuscular junction (NMJ) — the synapse between motor nerve and muscle. The genetic defect disrupts normal neuromuscular transmission, producing muscle weakness that fluctuates with activity, is worse after exertion, and is present from birth or early childhood.

Not autoimmune

Congenital Myasthenic Syndrome is GENETIC, not autoimmune. Unlike Myasthenia Gravis — which is caused by antibodies attacking the NMJ — CMS is caused by inherited gene mutations. It does not respond to immunosuppression. It is treated with specific medications that depend on which gene is mutated.

How many genes

40 different genes have been reported to cause CMS, affecting presynaptic, synaptic, and postsynaptic components of the NMJ. Each gene mutation produces a slightly different clinical pattern and, critically, responds to different medications. Getting the genetic diagnosis right is essential for safe and effective treatment.

India's largest cohort

The largest genetic characterisation of CMS from India was published in Brain 2024 — 156 patients from 141 families. The most common gene was CHRNE (39.4%), followed by DOK7 (14.4%), DPAGT1 (9.8%), GFPT1 (7.6%), and MUSK (6.1%). Novel genes MACF1 and TEFM were identified for the first time in this cohort. Eight variants were found to be geographically specific to the Indian subcontinent.

The consanguinity factor

Most CMS genes are autosomal recessive — requiring a mutation in both copies of the gene. The higher rates of consanguineous marriage in South India, including Telangana and Andhra Pradesh, increase the probability of recessive CMS conditions in children from first-cousin marriages. The Indian cohort shows a higher frequency of glycosylation-gene CMS (DPAGT1, GFPT1, GMPPB) than European cohorts — likely reflecting this consanguinity pattern.

Treatment is gene-specific

Pyridostigmine (acetylcholinesterase inhibitor) works well for CHRNE and RAPSN mutations but can WORSEN patients with COLQ mutations. Salbutamol (albuterol, a beta-2 agonist) is effective for DOK7, MUSK, and AGRN mutations. Getting the wrong drug for the wrong genotype can cause significant harm.

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About This Condition

Myasthenia That Is Not Myasthenia Gravis

A 3-year-old girl in Hyderabad has had drooping eyelids since early infancy. She tires easily — when she plays, her eyelids droop more, and if she runs, her legs give way after a short distance. She was initially told she had Myasthenia Gravis, and was tested for AChR antibodies — negative. She was given pyridostigmine at a standard MG dose. She appeared to improve slightly, then plateaued. She is now 3 years old, still symptomatic, and her parents are asking why their daughter, who has been on pyridostigmine for two years, is not getting better.

At KIMS Neuroscience, the history is reconsidered from the start. Myasthenia Gravis in children aged 3 with a negative antibody panel and a partially effective response to pyridostigmine since infancy: this is Congenital Myasthenic Syndrome until proven otherwise. A comprehensive CMS gene panel is ordered. The result: homozygous mutation in CHRNE — the epsilon subunit of the acetylcholine receptor. This is the most common CMS gene in India (present in 39.4% of the Indian CMS cohort). The specific mutation is one of eight found to be geographically specific to the Indian subcontinent.

Congenital Myasthenic Syndrome (CMS) is not one disease. It is a family of approximately 40 distinct genetic conditions, each caused by a mutation in a different gene encoding a component of the neuromuscular junction. Each produces a slightly different clinical phenotype, and each responds to a different treatment. The most important clinical principle in CMS management is: do not treat the symptom with a generic anti-myasthenic drug. Identify the gene. The gene determines the drug. The wrong drug for the wrong genotype does not just fail to help — it can actively harm the patient.

India has a disproportionately high burden of CMS relative to Western populations, driven by higher rates of consanguineous marriage that allow recessive mutations to express in children. The landmark Indian CMS cohort study published in Brain 2024 — 156 patients from 141 families, the largest Indian CMS dataset ever assembled — identified eight CMS gene variants specific to the Indian subcontinent. This is Indian data, characterising an Indian disease pattern, guiding Indian clinical practice.

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Understanding the Disease

How CMS Differs from Myasthenia Gravis

The two conditions share the final common pathway — impaired neuromuscular junction transmission producing fatigable muscle weakness — but their causes, ages of presentation, antibody profiles, and treatments are entirely different.

CMS is genetic; MG is autoimmune

CMS is caused by inherited gene mutations that disrupt the structural or functional components of the NMJ from the moment of birth. There are no antibodies against AChR, MuSK, or LRP4 in CMS. Immunosuppressive therapy (prednisolone, azathioprine, IVIG, plasmapheresis, thymectomy) has NO role in CMS treatment. Conversely, the gene-specific drugs used in CMS (salbutamol for DOK7) are not used in standard MG.

CMS presents in infancy or early childhood; MG peaks in adults

CMS is present from birth or the first months of life. Mothers may report reduced fetal movements in the third trimester. Neonates may have severe hypotonia, feeding difficulty, and respiratory failure from birth (severe forms). Toddlers typically present with fatigable ptosis, weakness worsening after activity, and motor developmental delay. MG in children (juvenile MG) does occur, but is typically AChR or MuSK antibody positive. Seronegative myasthenia in a child should be considered CMS until genetically excluded.

Each CMS gene requires a specific treatment

Pyridostigmine — the standard drug for MG — works for some CMS subtypes (particularly AChR deficiency from CHRNE, RAPSN mutations) and is harmful for others (COLQ — the synaptic acetylcholinesterase deficiency, where adding more pyridostigmine to an already impaired cholinesterase system produces a cholinergic crisis). Salbutamol (albuterol, a beta-2 adrenergic agonist) is effective for DOK7, MUSK, and AGRN CMS subtypes. The gene result is not an academic exercise — it is the prescription.

CMS is lifelong and stable or slowly progressive; MG fluctuates with autoimmune activity

CMS does not have the autoimmune flares of MG — it is a stable genetic condition with a characteristic, relatively predictable clinical course that is genotype-specific. However, some CMS subtypes progress slowly over time, and all CMS patients require lifelong monitoring of respiratory function, swallowing, and motor development.

Recognising CMS

How CMS Presents — Recognising It at Different Ages

CMS does not have a single face. The presentation varies by age and gene. Recognising the patterns is the first step to a correct genetic diagnosis.

The Neonate — Respiratory Failure and Feeding Difficulty

Severe CMS (particularly RAPSN and CHAT mutations) can present at birth with severe hypotonia, respiratory failure requiring ventilation, and inability to feed. The diagnosis in these neonates requires urgent genetic testing and is life-saving — the correct drug initiated within days of birth can produce dramatic improvement. In the Indian context, a severely hypotonic neonate born to a consanguineous couple — particularly from Telangana, Andhra Pradesh, Karnataka, or Tamil Nadu — should have CMS included in the differential of floppy infant alongside SMA and other neuromuscular conditions.

The Infant and Toddler — Ptosis, Fatigability, and Motor Delay

The most common CMS presentation seen at KIMS: a child between 6 months and 3 years with bilateral ptosis (particularly worse after activity and at the end of the day), a weak cry, feeding difficulties, and slower-than-expected motor development. The child may be unable to run without falling after short distances. Strength improves after rest and worsens with sustained activity — the fatigability pattern. AChR antibodies are negative. Thymus is normal. The diagnosis of MG has been considered but the antibody result and age of presentation should prompt CMS workup.

The Child and Adolescent — Limb-Girdle Pattern

Several CMS subtypes — particularly DOK7, GMPPB, GFPT1, and DPAGT1 mutations — present with a predominantly limb-girdle pattern (proximal leg and arm weakness) rather than the classic ptosis-and-fatigability picture. These are frequently misdiagnosed as Limb-Girdle Muscular Dystrophy — which they clinically resemble. The distinction: CMS limb-girdle weakness has a fatigability component (worse after exercise, better after rest), while LGMD typically does not. EMG showing a decremental response on repetitive nerve stimulation is a key distinguishing finding. In the Indian cohort, glycosylation gene mutations (GMPPB, GFPT1, DPAGT1) accounted for 21.3% of cases — higher than in European cohorts — and commonly produced the limb-girdle pattern.

The consanguinity clinical trigger — specific to South India

When a child from a consanguineous family (parents who are first or second cousins) presents with any combination of: fatigable muscle weakness, ptosis worse after activity, weakness since infancy or early childhood, and negative MG antibodies — the probability of CMS is high. Both parents carry one copy of a recessive CMS gene mutation, and the child has inherited two copies. This pattern is more common in Telangana, Andhra Pradesh, Karnataka, and Tamil Nadu than in the national average. At KIMS, consanguinity is specifically elicited in the family history of every child presenting with NMJ-pattern weakness.

Indian Cohort Data

The Indian CMS Gene Landscape — The Brain 2024 Cohort

The largest characterisation of CMS in India was published in Brain 2024 (Polavarapu et al., NIMHANS, Bangalore) — 156 genetically diagnosed patients from 141 families. This study defined which genes are most common in India, which variants are India-specific, and which treatments work for which genotypes. The genes most important for clinical practice at KIMS are summarised below.

CHRNE

39.4% — most common in India

AChR epsilon subunit dysfunction. Classic fatigable ptosis and weakness. Most common CMS gene globally and in India. Two India-specific variants identified. Autosomal recessive. Treatment: Pyridostigmine — responds well. 3,4-DAP added for inadequate response.

DOK7

14.4% — second most common in India

Limb-girdle pattern: proximal leg weakness dominant. Ptosis may be absent or mild. Fatigability prominent. Often misdiagnosed as LGMD. Autosomal recessive. Treatment: Salbutamol (albuterol) — pyridostigmine typically worsens or provides no benefit. Salbutamol is first-line.

DPAGT1

9.8% — higher in India vs Europe

Glycosylation gene. Limb-girdle and cognitive involvement. Higher prevalence in India vs Europe (likely consanguinity). Autosomal recessive. India-specific variant DPAGT1 p.T380I identified. Treatment: Pyridostigmine + salbutamol combination. Both needed for optimal response.

GFPT1

7.6%

Glycosylation gene. Limb-girdle. Often presents in teens or adulthood. Tubular aggregate myopathy on biopsy. Autosomal recessive. Treatment: Pyridostigmine + salbutamol. Both required.

MUSK

6.1%

Postsynaptic. Bulbar and respiratory involvement prominent. Can have fetal akinesia. Autosomal recessive in CMS (unlike MG where MuSK antibodies cause autoimmune disease). Treatment: Salbutamol — pyridostigmine worsens. Ephedrine alternative.

GMPPB

5.3%

Glycosylation gene. Limb-girdle + cognitive + structural muscle (dystrophic) features. Serum CK elevated — resembles LGMD on initial assessment. Autosomal recessive. Treatment: Pyridostigmine + salbutamol. Requires combined therapy.

COLQ

4.5% — pyridostigmine contraindicated

Synaptic acetylcholinesterase deficiency. Fatigable ptosis, ophthalmoplegia, scoliosis, respiratory involvement. Autosomal recessive. ⚠ PYRIDOSTIGMINE CONTRAINDICATED — causes cholinergic crisis. Salbutamol or ephedrine ONLY.

COLQ CMS: The Drug That Causes Harm — Critical Safety Point

COLQ mutations cause deficiency of the collagen tail that anchors acetylcholinesterase to the NMJ basal lamina. Without this anchor, acetylcholine accumulates excessively in the synapse. Adding pyridostigmine — which further prevents acetylcholine breakdown — causes cholinergic crisis: excessive acetylcholine stimulation producing sweating, bradycardia, bronchospasm, and worsening weakness.

COLQ patients who receive pyridostigmine deteriorate. At KIMS, every CMS patient has their gene identified before any drug is prescribed, and the KIMS team specifically confirms COLQ has been excluded before pyridostigmine is started.

Salbutamol is the safe treatment for COLQ.

Diagnosis at KIMS

Diagnosis at KIMS — From Fatigability Testing to the Gene Panel

Detailed clinical assessment — fatigability testing

The hallmark of CMS is fatigable weakness — weakness that increases with sustained activity and improves with rest. At KIMS: sustained upgaze test (patient looks upward for 60 seconds — ptosis develops or worsens in CMS), sustained arm elevation (arms held horizontal for 60 seconds — progressive failure to hold), gait assessment after running (child asked to run for 2 minutes — gait deteriorates). The pattern, age of onset, family history (consanguinity, affected siblings), and maternal obstetric history (reduced fetal movements) guide the diagnostic pathway.

Acetylcholine receptor and MuSK antibodies — to exclude autoimmune MG

AChR, MuSK, and LRP4 antibodies are sent to exclude seronegative autoimmune juvenile MG. All are negative in CMS — but their absence is not sufficient to diagnose CMS alone; genetic testing is required.

Repetitive nerve stimulation — the NMJ fingerprint

In most CMS subtypes, RNS at 3Hz shows a decremental response of the compound muscle action potential (>10% decrement) — the same pattern as in MG. This confirms NMJ dysfunction but does not distinguish CMS from MG. Some CMS subtypes (COLQ, SCCMS) show a distinctive RNS pattern: repetitive single stimulation at rest produces multiple CMAPs from a single nerve stimulus — the so-called repetitive CMAP, which is virtually pathognomonic of COLQ and SCCMS CMS. Identifying this pattern at KIMS triggers immediate COLQ genetic testing.

CMS gene panel (NGS) — the definitive test

A comprehensive next-generation sequencing (NGS) panel covering all known CMS genes is the definitive diagnostic test. From a single blood sample, all 40+ known CMS genes are sequenced simultaneously, identifying the specific mutation and guiding treatment. At KIMS, the panel result typically returns in 4–6 weeks. In severe or rapidly deteriorating patients, a targeted hotspot panel covering the most common Indian CMS genes (CHRNE, DOK7, DPAGT1, GFPT1, MUSK, COLQ, RAPSN) can provide a faster answer within 2–3 weeks, covering approximately 75–80% of Indian CMS cases.

Muscle biopsy (selected cases)

Muscle biopsy is not routinely required for CMS diagnosis but is useful in: (1) cases where the gene panel does not yield a definitive result; (2) tubular aggregate myopathy pattern on biopsy — characteristic of GFPT1 CMS; (3) GMPPB CMS where biopsy shows both NMJ defects and muscular dystrophy features. Biopsy for electron microscopy of NMJ can directly visualise structural abnormalities in selected subtypes.

Respiratory and swallowing assessment — at diagnosis and annually

Pulmonary function tests, overnight oximetry, and swallowing assessment are performed at KIMS at the time of diagnosis for all CMS patients. Respiratory involvement is most severe in RAPSN, CHAT, and MUSK CMS. Annual monitoring allows early intervention with non-invasive ventilation before crisis develops.

Treatment

Treatment at KIMS — Gene-First, Drug-Second

Pyridostigmine — When It Works and When It Does Not

Pyridostigmine (an acetylcholinesterase inhibitor) is the standard first-line drug for CMS subtypes with AChR deficiency — the largest category in India. It increases the amount of acetylcholine available at the NMJ by slowing its breakdown. At KIMS, pyridostigmine is started once COLQ is excluded (either by gene panel result or by the absence of repetitive CMAP on EMG). Dosing is weight-based, and the response is monitored clinically at each visit.

When NOT to Give Pyridostigmine

Contraindicated and Harmful CMS Subtypes

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COLQ mutation: absolute contraindication (cholinergic crisis).

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SCCMS (slow-channel CMS): pyridostigmine worsens the prolonged ACh channel opening that characterises this subtype — quinidine or fluoxetine are used instead.

•

DOK7 and MUSK: pyridostigmine typically provides no benefit and may worsen some patients; salbutamol is the treatment.

At KIMS, pyridostigmine is never started for suspected CMS without either the gene result confirming safety or a negative repetitive CMAP on EMG.

Salbutamol Therapy

Salbutamol — The Treatment That Transforms DOK7 CMS

Salbutamol (albuterol) — a beta-2 adrenergic agonist widely known as a bronchodilator in India — has a specific and robust evidence base in DOK7 CMS. It activates beta-2 receptors at the NMJ, increasing the density of AChR clusters and improving neuromuscular transmission by a mechanism independent of cholinesterase inhibition.

In the Indian cohort, DOK7 was the second most common CMS gene (14.4%), and all DOK7 patients in the cohort showed good response to salbutamol.

Oral salbutamol (not inhaled) is used in CMS: 2–4mg twice daily, titrated upward based on response and tolerance. Side effects monitored at KIMS: tachycardia, tremor, and hypokalaemia.

Salbutamol is also used as add-on therapy in: MUSK, AGRN, and glycosylation gene (DPAGT1, GFPT1, GMPPB) CMS.

Advanced Therapy

3,4-Diaminopyridine (3,4-DAP) — For Insufficient Response

3,4-DAP (amifampridine) — the same drug used in LEMS — blocks potassium channels in the nerve terminal and increases acetylcholine release.

It is used in CMS subtypes that do not respond adequately to pyridostigmine alone, including some CHRNE and RAPSN patients, and as add-on therapy in glycosylation gene CMS.

Available through specialist import at KIMS.

Genetic Counselling

Genetic Counselling and Reproductive Planning

Because most CMS genes are autosomal recessive, both parents of an affected child are carriers. The recurrence risk for future pregnancies is 25%. At KIMS, genetic counselling is offered at the time of diagnosis, with attention to the specific Indian context: higher carrier frequencies in some South Indian communities, and the eight India-specific CMS gene variants identified in the Brain 2024 cohort.

For a confirmed CMS family at KIMS, genetic counselling spans carrier testing, prenatal diagnosis, pre-implantation options, and structured cascade testing for the extended family — particularly important when an India-specific recurrent variant is the cause.

What KIMS arranges for the affected family

Carrier testing for siblings of both parents — relevant given the high carrier frequency in some South Indian communities for specific CMS variants

Prenatal diagnosis by chorionic villus sampling (CVS) at 11–13 weeks for future pregnancies

Pre-implantation genetic diagnosis (PGD) via IVF — selecting unaffected embryos before transfer

Cascade testing for the extended family — particularly relevant when India-specific recurrent variants are identified

Recurrence risk for future pregnancies of an affected couple is 25%, since most CMS genes are autosomal recessive — both parents are carriers

Related Conditions

Congenital Myasthenic Syndrome belongs to the family of neuromuscular disorders evaluated and managed at KIMS Neuroscience:

Spinal Muscular Atrophy Neuromuscular Disorders (Master)

FAQs

Frequently Asked Questions

Yes — and this scenario is common at KIMS. In India, CMS is frequently diagnosed late because the initial presentation — fatigable weakness, ptosis, negative AChR antibodies — leads to a treatment trial of pyridostigmine without a definitive genetic diagnosis. Some CMS subtypes (CHRNE) respond well to pyridostigmine. Others (DOK7, MUSK) do not respond or may worsen. The absence of full improvement after two years on pyridostigmine in a child with seronegative myasthenia should always trigger genetic testing for CMS. At KIMS, the CMS gene panel from a blood sample identifies the specific gene within 4–6 weeks and determines the correct treatment. Please call 040-44885000 to arrange a KIMS reassessment.

Yes — oral salbutamol is a safe and effective treatment for DOK7 CMS and is supported by strong clinical evidence. The drug is the same as the common bronchodilator used in asthma, but in CMS it is given orally (tablet or syrup) at doses specifically calibrated for neuromuscular benefit rather than inhaled for the lung. Side effects to monitor — which KIMS checks at every follow-up — include a mild increase in heart rate (tachycardia), mild hand tremor, and a possible drop in blood potassium (hypokalaemia). These are all manageable at the doses used. In the large Indian CMS cohort study, all DOK7 patients showed good response to salbutamol. The improvement can take 4–8 weeks to reach its maximum effect. Please call 040-44885000 to confirm dosing and follow-up arrangements.

COLQ mutations cause a deficiency of the enzyme that anchors acetylcholinesterase to the NMJ. Without this enzyme, acetylcholine already accumulates abnormally in the synapse. Pyridostigmine works by blocking the remaining acetylcholinesterase — further preventing ACh breakdown. In COLQ-CMS, this produces cholinergic excess: too much acetylcholine at the synapse causes sweating, bradycardia, bronchospasm, intestinal cramps, and worsening muscle weakness through receptor desensitisation. This is a cholinergic crisis — the same mechanism as organophosphate poisoning. In COLQ-CMS, pyridostigmine is absolutely contraindicated. The correct treatment is salbutamol or ephedrine. At KIMS, this is identified before any drug is prescribed by checking for the repetitive CMAP pattern on EMG (almost pathognomonic of COLQ) and by the gene result. If your child has COLQ-CMS, a KIMS medication alert card is issued to carry at all times. Please call 040-44885000.

CHRNE CMS is autosomal recessive — your daughter has mutations in both copies of the CHRNE gene. For her child to have CMS, the child would need to inherit one CHRNE mutation from her AND one from the other parent (who would need to be a carrier). If the other parent is not a carrier of a CHRNE mutation, none of their children will be affected (though all children will be carriers). If the other parent is a carrier, each pregnancy would have a 25% chance of CMS and a 50% chance of being a carrier. Before pregnancy, the partner should be tested for CHRNE carrier status at KIMS. If both are carriers, prenatal diagnosis (CVS) or pre-implantation genetic diagnosis (PGD) via IVF can identify whether the fetus or embryo has inherited the condition. During pregnancy itself, pyridostigmine can be continued at the doses required to manage symptoms — it does not affect fetal development when used at therapeutic doses. Please call 040-44885000 to arrange pre-conception genetic counselling.

Yes — lifelong specialist follow-up is important even for a child who is clinically stable on treatment. The reasons at KIMS: (1) Respiratory function changes over time in CMS, particularly in DOK7 where diaphragm weakness can develop slowly. Annual pulmonary function tests detect decline before it becomes a crisis. (2) Salbutamol dosing often needs adjustment as the child grows — weight-based dose recalculation is done at each visit. (3) New symptoms may develop that require assessment: scoliosis develops in some CMS subtypes with prolonged axial muscle weakness; swallowing difficulty can emerge in adolescence even in patients who were previously well. (4) Transition to adult neuromuscular services at KIMS needs to be planned as he approaches adulthood. Please call 040-44885000 to register for the KIMS CMS long-term follow-up programme.

CMS is genuinely rare — estimated at fewer than 1 in 100,000 children — but it is likely under-diagnosed in India, particularly in rural areas where access to genetic testing is limited. India's higher rates of consanguineous marriage increase the prevalence of recessive CMS conditions compared to Western populations. The landmark Indian CMS cohort study (Brain 2024, 156 patients from NIMHANS Bangalore) identified 8 CMS gene variants that are geographically specific to the Indian subcontinent — meaning there are mutations that have never been described outside India and are particularly relevant for Indian families. The glycosylation gene CMS subtypes (DPAGT1, GFPT1, GMPPB) were proportionally much more common in the Indian cohort than in European studies — likely reflecting the consanguinity pattern in South India. At KIMS, awareness of the Indian CMS gene landscape means that the right genes are tested in the right order for Indian patients. Call 040-44885000.

The full CMS gene panel result typically returns in 4–6 weeks at KIMS. A targeted hotspot panel covering the most common Indian CMS genes (which account for approximately 75–80% of Indian CMS cases) can provide a result in 2–3 weeks. While awaiting the result, KIMS manages symptoms based on the clinical picture and EMG findings. If the RNS shows no repetitive CMAP — making COLQ unlikely — a cautious trial of pyridostigmine at a low dose may be started with close monitoring for any worsening (the signal that would suggest COLQ). If the EMG does show a repetitive CMAP, suggesting COLQ or SCCMS, pyridostigmine is withheld entirely until the gene result is available. The child is seen weekly by KIMS while the result is pending if the clinical situation requires it, with emergency contact at 040-46324365 if the child deteriorates. Call 040-44885000 to arrange the initial KIMS assessment.

Fact	Details
CMS: genetic, NOT autoimmune	Gene mutations disrupt NMJ function · AChR antibodies NEGATIVE · Does NOT respond to immunosuppression · Treat with gene-specific medications only
India's largest cohort (Brain 2024)	156 patients, 141 families · CHRNE 39.4% (most common) · DOK7 14.4% · DPAGT1 9.8% · GFPT1 7.6% · MUSK 6.1% · 8 India-subcontinent-specific variants identified
Drug-gene rules	CHRNE/RAPSN: pyridostigmine effective · COLQ: pyridostigmine CONTRAINDICATED (worsens) · DOK7/MUSK/AGRN: salbutamol effective · Glycosylation genes: variable response · Gene panel result required before prescribing
Consanguinity in South India	Higher frequency of autosomal recessive CMS in Telangana/AP · Glycosylation-gene CMS (DPAGT1, GFPT1, GMPPB) higher than European cohorts · Consanguineous family history raises suspicion
Diagnosis workup	Repetitive nerve stimulation (decremental response 3 Hz) · AChR/MuSK antibodies (NEGATIVE in CMS) · CMS gene panel (40 genes, single blood sample) · Maternal antibody testing to exclude neonatal autoimmune MG
40 genes — each with clinical implications	Presynaptic: CHAT, SLC18A3, SNAP25 · Synaptic: COLQ, LAMA5 · Postsynaptic: CHRNA1/B1/D1/E1, RAPSN, DOK7, MUSK, AGRN · Glycosylation: DPAGT1, GFPT1, GMPPB · Structural: novel genes MACF1, TEFM (first identified in the Indian cohort)
Contact	040-44885000 · Emergency (respiratory distress, inability to handle secretions): 040-46324365

A child who has had drooping eyelids since infancy. Weakness that is always worse after play. Parents who have been told it is MG — but the antibodies are negative and pyridostigmine has not fully worked in two years. The answer is genetic. And the right drug depends entirely on which gene it is.

At KIMS Neuroscience, Secunderabad, Hyderabad, every child with suspected Congenital Myasthenic Syndrome receives the complete KIMS assessment: fatigability testing, RNS to detect the COLQ-specific repetitive CMAP pattern before any drug is started, full CMS gene panel from a blood sample identifying the specific gene and mutation, and gene-specific treatment starting with the correct drug for the correct genotype. Our approach is grounded in the largest Indian CMS cohort data (Brain 2024, 156 patients), including identification of 8 India-specific CMS gene variants. We do not give pyridostigmine to COLQ. We do not give pyridostigmine to DOK7. We give the right drug for the right gene.

040-44885000

International enquiries: info@kimsneurosciences.com