neuromuscular disorders, spinal muscular atrophy, duchenne muscular dystrophy, becker muscular dystrophy, facioscapulohumeral dystrophy, limb girdle muscular dystrophy, myotonic dystrophy type 1, muscular dystrophy types, genetic muscle disorders, pediatric neuromuscular diseases, dystrophin gene mutation, SMN1 gene, CTG repeat expansion, muscle weakness disorders, proximal muscle weakness, gowers sign, myotonia, floppy infant causes, muscle degeneration diseases, neuromuscular disease diagnosis
Paediatrics
Neuromuscular Disorders Explained SMA Duchenne Becker FSHD Limb Girdle Myotonic Dystrophy Guide
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Neuromuscular disorders are conditions affecting motor neurons peripheral nerves neuromuscular junction or muscles leading to weakness hypotonia and impaired motor function in children.
Spinal muscular atrophy is an autosomal recessive disorder caused by SMN1 gene mutation leading to degeneration of anterior horn cells presenting with hypotonia weakness areflexia and tongue fasciculations in infants.
SMA is classified into type 1 severe infantile type 2 intermediate and type 3 mild juvenile form based on age of onset and motor milestones achieved.
Duchenne muscular dystrophy is an X linked disorder caused by absence of dystrophin presenting with progressive proximal weakness Gowers sign calf pseudohypertrophy and cardiomyopathy.
Duchenne is caused by frameshift mutation leading to absent dystrophin with early severe disease while Becker is due to non frameshift mutation with partially functional dystrophin and milder later onset disease.
Facioscapulohumeral dystrophy is an autosomal dominant disorder characterized by facial weakness scapular winging and asymmetric muscle involvement due to D4Z4 deletion on chromosome 4.
Limb girdle muscular dystrophy is a group of genetic disorders causing progressive weakness of shoulder and pelvic girdle muscles with variable inheritance patterns and no significant facial involvement.
Myotonic dystrophy type 1 is an autosomal dominant disorder caused by CTG repeat expansion in DMPK gene leading to myotonia distal weakness cataracts cardiac conduction defects and endocrine abnormalities.
Myotonia is delayed muscle relaxation after contraction clinically seen as difficulty releasing grip or percussion myotonia and confirmed by myotonic discharges on EMG.
Gowers sign is the use of hands to climb up the thighs while rising from the floor indicating proximal muscle weakness and is classically seen in Duchenne muscular dystrophy.
Diagnosis involves clinical examination serum CK levels genetic testing EMG studies and sometimes muscle biopsy depending on the suspected condition.
Creatine kinase is elevated due to muscle fiber breakdown and leakage of intracellular enzymes into the bloodstream.
Complications include cardiomyopathy respiratory failure scoliosis and loss of ambulation typically by early adolescence.
Steroids such as prednisolone and deflazacort help delay disease progression preserve muscle strength and prolong ambulation.
Treatments include nusinersen which modifies SMN2 splicing risdiplam and gene therapy with onasemnogene abeparvovec to increase SMN protein production.
Anticipation refers to increasing severity and earlier onset of disease in successive generations due to expansion of CTG repeats.
FSHD involves facial and scapular muscles with asymmetry whereas limb girdle dystrophy primarily affects proximal limb muscles without facial involvement.
Respiratory failure occurs due to weakness of respiratory muscles leading to hypoventilation and reduced cough effectiveness.
Genetic testing confirms diagnosis identifies mutation type guides prognosis and enables genetic counseling for families.
Red flags include delayed motor milestones hypotonia progressive weakness loss of previously acquired skills calf hypertrophy and family history of similar illness.
