Discuss differential diagnosis of a floppy infant. Write a short note on clinical and laboratory characteristics of Werdnig-Hoffman disease
Floppy infant:
Differential Diagnosis
Central nervous system
- Chromosomal disorders
- Inborn errors of metabolism
- Cerebral dysgenesis
- Trauma ( cerebral/spinal)
Motor neuron
- Spinal Muscular Atrophy
Nerve
- Peripheral neuropathies
Neuromuscular junction
- Myasthenia syndromes
- Infantile botulism
Muscle
- Congenital myopathies
- Metabolic myopathies
- Congenital muscular dystrophy
- Congenital myotonic dystrophy
Werdnig Hoffman disease:
This is type 1 Spinal Muscular Atrophy (SMA). This type constitute about 50-60% cases of SMA. There are three subtypes
- Type 1A
- Type 1B
- Type 1C
Clinical features:
Type 1A:
Age of onset: Prenatal
Life expectancy: <6 months
Milestones achieved: none
Features:
- Severe weakness @ birth
- Profound hypotonia
- Areflexia
- Paradoxical abdominal breathing, bell shaped chest, weak cough
- Early respiratory failure
- Joint contractures
Type 1B & 1C
Age of onset:
- Type 1B - 0-3 months
- Type 1C - 3-6 months
Milestones:. Never sits without support
Features:
- Weakness
- Frog leg posture, hypotonia
- Tongue fascinations
- Hyporeflexia , areflexia
- Sucking & swallowing difficulties
- Respiratory failure
Laboratory findings
Serum creatinine kinase: mildly elevated (2-4 fold) not more than 10 times
Electrocardiography: lead II shows a base line tremor representing muscle fibrillations.
Motor Nerve conduction test: Normal
Molecular genetic test: Homozygous deletion of exon 7
Muscle biopsy: not done nowadays, gaint type 1 fibers are seen with in muscle facicles of severely atrophic fibres
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