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SMA type 1 — RACP Paediatrics MCQ

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ModerateNeurologySMA type 1RACP Paediatrics

A term neonate has severe generalised hypotonia with absent deep tendon reflexes and tongue fasciculations. There is paradoxical breathing pattern with a bell-shaped chest. The infant is alert with bright eyes. Creatine kinase is normal. What is the most likely diagnosis?

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Correct answer: D — Spinal muscular atrophy type 1

Severe hypotonia with areflexia, tongue fasciculations, paradoxical breathing, bell-shaped chest, and preserved cognition (alert facies) in a neonate is the classic presentation of spinal muscular atrophy type 1 (Werdnig-Hoffmann disease). It is caused by SMN1 gene mutation (autosomal recessive). Now detected on newborn screening in Australia. Nusinersen, risdiplam, or gene therapy (onasemnogene) are available treatments.

Reference: RCH Melbourne – 2023 – Floppy Infant CPG; RACP Paediatric Curriculum – Neurology