⚡ Neuromuscular Disorders · Quick Reference

Screening tests, definitive diagnosis, most accurate treatment & mnemonics – based on Nelson Textbook of Pediatrics (22nd Ed). Perfect for rapid recall and exam prep.

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Duchenne MD (DMD)
🩺 SCREENING
CK (↑↑↑ >10,000 IU/L) — newborn screening pilot programs; male with delayed walking & Gowers sign.
🔬 CONFIRMATORY DIAGNOSIS
Dystrophin gene (DMD) deletion/duplication (MLPA) → 65% deletions; NGS; muscle biopsy (absent dystrophin).
💊 MOST ACCURATE TREATMENT
Corticosteroids (prednisone 0.75 mg/kg/day or deflazacort 0.9 mg/kg/day) → prolong ambulation. Exon skipping (eteplirsen, golodirsen). Gene therapy: Elevidys (ages 4-5). Cardiac ACE inhibitors.
🧠 MNEMONIC: “DMD: Delete Me! CK high, Gowers, steroids prolong” – Deletion, Marked CK, Gowers sign, Deflazacort/ prednisone.
Becker MD (BMD)
🩺 SCREENING
Elevated CK (1,000-15,000), proximal weakness, calf hypertrophy, family history X-linked.
🔬 CONFIRMATORY DIAGNOSIS
Dystrophin gene (in-frame deletion/duplication) → abnormal but present dystrophin; muscle biopsy shows reduced/ abnormal dystrophin.
💊 MOST ACCURATE TREATMENT
Cardiac surveillance (annual echo/ECG). ACE inhibitors / β-blockers for cardiomyopathy. Steroids less proven; supportive care.
🧠 MNEMONIC: “BMD = Better prognosis, in-frame, later onset”
Myotonic Dystrophy (DM1)
🩺 SCREENING
Clinical myotonia (grip/percussion), cataracts, frontal balding, cardiac conduction defects; family history with anticipation.
🔬 CONFIRMATORY DIAGNOSIS
DMPK CTG repeat expansion (>50 repeats) → Southern blot / TP-PCR.
💊 MOST ACCURATE TREATMENT
Mexiletine for myotonia. Pacemaker for heart block. Annual ECG/Holter. Treat endocrine, respiratory support (NIPPV).
🧠 MNEMONIC: “MYOTONIA: Mexiletine, Yearly ECG, Ophthalmology, Thyroid, O2 sleep, NIPPV, Insulin screen, Arrhythmia watch.”
Facioscapulohumeral MD (FSHD)
🩺 SCREENING
Facial weakness (horizontal smile), scapular winging, asymmetric weakness, hearing loss, Coats disease (retinal telangiectasias).
🔬 CONFIRMATORY DIAGNOSIS
D4Z4 contraction (4q35) → ≤10 repeats (FSHD1). SMCHD1 sequencing (FSHD2).
💊 MOST ACCURATE TREATMENT
Scapulothoracic fusion (if severe winging), ankle-foot orthosis, hearing aids, laser for Coats disease. Pain management (gabapentin).
🧠 MNEMONIC: “FSHD = Face, Scapula, Hearing, D4Z4” – Face weakness, Scapular winging, Hearing loss, D4Z4 contraction.
Limb-Girdle MD (LGMD)
🩺 SCREENING
Proximal limb-girdle weakness, elevated CK (very high in sarcoglycanopathies).
🔬 CONFIRMATORY DIAGNOSIS
Muscle biopsy (immunohistochemistry for sarcoglycans, dysferlin, calpain, FKRP) → LGMD gene panel (CAPN3, DYSF, SGCA, FKRP, ANO5, etc.).
💊 MOST ACCURATE TREATMENT
Cardiac surveillance (FKRP, sarcoglycans). Physical therapy, orthoses. Genetic counseling. Steroids controversial.
🧠 MNEMONIC: “LGMD: Look at Genetics — Muscle Biopsy, Defect specific”
Myasthenia Gravis (MG)
🩺 SCREENING
Fatigable ptosis, diplopia, bulbar weakness, worse at evening. Ice pack test (improves ptosis).
🔬 CONFIRMATORY DIAGNOSIS
Anti-AChR antibody (70-80%) / MuSK. Repetitive nerve stimulation → decremental response (>10%). SFEMG (most sensitive).
💊 MOST ACCURATE TREATMENT
Pyridostigmine, prednisone, IVIG/plasmapheresis for crisis. Thymectomy (AChR+, age > puberty).
🧠 MNEMONIC: “MG: Myasthenia = Muscles Get Fatigued, anti‑AChR, Edrophonium, Pyridostigmine, Thymectomy”
Spinal Muscular Atrophy (SMA)
🩺 SCREENING
Newborn screening (SMN1 deletion) – hypotonia, areflexia, tongue fasciculations.
🔬 CONFIRMATORY DIAGNOSIS
SMN1 homozygous deletion (MLPA or real-time PCR); SMN2 copy number (prognosis).
💊 MOST ACCURATE TREATMENT
Nusinersen (IT ASO), Risdiplam (oral), Zolgensma (IV gene therapy age <2y) – disease modifying.
🧠 MNEMONIC: “SMA: SMN1 deletion; Spinraza, Zolgensma, Risdiplam – early treatment saves motor neurons.”
Guillain-Barré Syndrome (GBS)
🩺 SCREENING
Acute ascending flaccid weakness, areflexia, preceding infection (Campylobacter, EBV, Zika).
🔬 CONFIRMATORY DIAGNOSIS
CSF cytoalbuminologic dissociation (protein ↑, WBC <10). NCS: demyelinating (AIDP) or axonal (AMAN). Anti-GQ1b (Miller Fisher).
💊 MOST ACCURATE TREATMENT
IVIG (2 g/kg) or plasmapheresis. Supportive: respiratory monitoring, pain control (gabapentin).
🧠 MNEMONIC: “GBS: Gait unsteady, Areflexia, CSF protein high, IVIG first line.”
Infantile Botulism
🩺 SCREENING
Constipation, weak cry, descending paralysis, ptosis, dilated pupils, poor feeding.
🔬 CONFIRMATORY DIAGNOSIS
Stool culture/toxin (mouse bioassay); EMG shows incremental response (rapid repetitive stimulation).
💊 MOST ACCURATE TREATMENT
BabyBIG (botulism immune globulin) IV, supportive respiratory care.
🧠 MNEMONIC: “Botulism: Bulbar first, Ophthalmoplegia, Toxin, Urgency for BabyBIG.”
CMT1A (PMP22 dup)
🩺 SCREENING
Pes cavus, hammer toes, distal muscle wasting (stork legs), areflexia, slow nerve conduction.
🔬 CONFIRMATORY DIAGNOSIS
PMP22 duplication (FISH/MLPA) – most common CMT. NCS: demyelinating (NCV <38 m/s).
💊 MOST ACCURATE TREATMENT
AFO, physical therapy, pain management (gabapentin). Avoid prolonged pressure. No curative drug.
🧠 MNEMONIC: “CMT1A = Charcot Marie Tooth One A: PMP22 duplication, AFO, Atrophy distal.”
HNPP (PMP22 deletion)
🩺 SCREENING
Episodic pressure palsies (foot drop after crossing legs, wrist drop).
🔬 CONFIRMATORY DIAGNOSIS
PMP22 deletion; nerve biopsy: tomaculous (sausage-shaped) myelin.
💊 MOST ACCURATE TREATMENT
Avoid compression; AFO; patient education; physical therapy.
🧠 MNEMONIC: “HNPP = Holiday Nerves Pressure Palsies – avoid crossing legs/elbows.”
Fabry Disease
🩺 SCREENING
Acroparesthesias (burning hands/feet), angiokeratomas, hypohidrosis, cornea verticillata.
🔬 CONFIRMATORY DIAGNOSIS
Leukocyte α-galactosidase A (low), GLA gene sequencing.
💊 MOST ACCURATE TREATMENT
Enzyme replacement (agalsidase alfa/beta) IV q2 weeks. Oral chaperone (migalastat) for amenable mutations.
🧠 MNEMONIC: “Fabry: Fingers burn, Angiokeratomas, α‑Galactosidase, ERT (agalsidase).”
Giant Axonal Neuropathy (GAN)
🩺 SCREENING
Kinky/frizzy hair, progressive neuropathy, ataxia, CNS white matter changes.
🔬 CONFIRMATORY DIAGNOSIS
GAN gene (gigaxonin) sequencing; nerve biopsy: giant axons (neurofilament accumulation).
💊 MOST ACCURATE TREATMENT
Supportive only (PT, orthotics, NIPPV). No curative treatment.
🧠 MNEMONIC: “GAN: Giant Axons, kinky hair, GAN gene, No cure.”
McArdle (GSD V)
🩺 SCREENING
Exercise intolerance, second wind phenomenon, myoglobinuria, cramping.
🔬 CONFIRMATORY DIAGNOSIS
Ischemic forearm test → no lactate rise; muscle biopsy absent myophosphorylase; PYGM sequencing.
💊 MOST ACCURATE TREATMENT
Pre‑exercise sucrose/glucose; avoid high-intensity anaerobic exercise; moderate aerobic conditioning.
🧠 MNEMONIC: “McArdle: Myoglobinuria, Cramps, Anaerobic no lactate, Rest – Give Carb (glucose).”
Pompe Disease (GSD II)
🩺 SCREENING
Infantile: cardiomegaly, hypotonia, macroglossia. Late‑onset: progressive myopathy.
🔬 CONFIRMATORY DIAGNOSIS
GAA enzyme (dried blood spot); GAA gene sequencing.
💊 MOST ACCURATE TREATMENT
Enzyme replacement – alglucosidase alfa (Myozyme).
🧠 MNEMONIC: “Pompe: Pump – Acid maltase deficient, ERT (Myozyme) for heart and muscle.”
Hypokalemic Periodic Paralysis
🩺 SCREENING
Episodic weakness after high-carb meal; low serum potassium.
🔬 CONFIRMATORY DIAGNOSIS
CACNA1S (Ca) or SCN4A (Na) mutations, ictal hypokalemia.
💊 MOST ACCURATE TREATMENT
Acute: oral potassium. Chronic: acetazolamide/dichlorphenamide.
🧠 MNEMONIC: “HypoKPP: Carb-load → K+ low, Acetazolamide, avoid carbs before sleep.”
CPT2 Deficiency
🩺 SCREENING
Recurrent myoglobinuria after prolonged exercise, fasting, cold, high-fat meal.
🔬 CONFIRMATORY DIAGNOSIS
Acylcarnitine profile (elevated C16, C18:1); CPT2 gene sequencing.
💊 MOST ACCURATE TREATMENT
Avoid fasting, pre‑exercise carbohydrates, MCT oil, IV glucose during illness.
🧠 MNEMONIC: “CPT2: Carnitine shuttle block – Fasting/Cold provoke; MCT oil, pre‑exercise glucose.”
Malignant Hyperthermia (MH)
🩺 SCREENING
Unexplained ↑ETCO2, masseter spasm, hyperthermia, rigidity after volatile anesthetics.
🔬 CONFIRMATORY DIAGNOSIS
RYR1 (70-80%) or CACNA1S mutations; muscle contracture test (IVCT).
💊 MOST ACCURATE TREATMENT
Dantrolene 2.5 mg/kg IV (repeat). Avoid triggers: TIVA (propofol) + nondepolarizing relaxants.
🧠 MNEMONIC: “MH = Dantrolene, Discontinue volatiles, Oxygen, Cooling, Hyperventilate.”
Familial Dysautonomia (FD)
🩺 SCREENING
Ashkenazi Jewish, alacrima (no tears), absent fungiform papillae, insensitivity to pain.
🔬 CONFIRMATORY DIAGNOSIS
IKBKAP (ELP1) gene mutation. Histamine test → absent flare.
💊 MOST ACCURATE TREATMENT
Autonomic crisis: clonidine, diazepam, carbidopa. Artificial tears, G‑tube for aspiration, fludrocortisone for hypotension.
🧠 MNEMONIC: “RILEY: Recurrent vomiting, alacrima, Jewish heritage, ELP1, Y?”
CIPA (HSAN IV)
🩺 SCREENING
Congenital insensitivity to pain, anhidrosis, recurrent hyperthermia, self‑mutilation.
🔬 CONFIRMATORY DIAGNOSIS
NTRK1 (TRKA) mutations.
💊 MOST ACCURATE TREATMENT
Cooling vests, protective care, dental extractions, avoid injuries.
🧠 MNEMONIC: “CIPA: Can’t feel Pain, Anhidrosis, NTRK1.”
Allgrove (Triple A) syndrome
🩺 SCREENING
Alacrima, achalasia, adrenal insufficiency (ACTH-resistant).
🔬 CONFIRMATORY DIAGNOSIS
AAAS gene mutation.
💊 MOST ACCURATE TREATMENT
Hydrocortisone (stress doses), esophageal dilatation, artificial tears.
🧠 MNEMONIC: “Triple A: Alacrima, Achalasia, Adrenal failure – AAAS.”
Lead Neuropathy (toxic)
🩺 SCREENING
Wrist drop/foot drop, basophilic stippling, abdominal colic, lead lines.
🔬 CONFIRMATORY DIAGNOSIS
Blood lead level (≥45 mcg/dL).
💊 MOST ACCURATE TREATMENT
Remove source, chelation: succimer (oral) or BAL+EDTA (encephalopathy).
🧠 MNEMONIC: “Lead: Lines (gingival), Encephalopathy, Anemia, Drop wrist.”
Nitrous Oxide Neuropathy
🩺 SCREENING
Recreational use (whippets), subacute combined degeneration (myelopathy), paresthesias.
🔬 CONFIRMATORY DIAGNOSIS
Low serum B12, elevated methylmalonic acid (MMA), MRI spine dorsal column T2 hyperintensity.
💊 MOST ACCURATE TREATMENT
High-dose IM B12 (cyanocobalamin) and avoidance.
🧠 MNEMONIC: “N2O: No B12, demyelination, treat with IM Cobalamin.”