Spinal muscular atrophy

Definition

Spinal muscular atrophy (SMA) is a progressive disorder with loss of anterior horn cells leading to muscle weakness and wasting. The weakness is typically symmetrical. Typically, upper motor neuron signs are absent and there is no sensory deficit. Feeding and swallowing can be affected, and involvement of respiratory muscles may occur. SMA is an autosomal recessive disorder linked to chromosome 5q13 and the disorder is caused by deletion or mutation of SMN 1 (spinal motor neuron 1) gene. The four types of SMA I, II, III and IV are categorised based on the age of onset of the disease and the ability to achieve motor milestones.

7 subordinate codes

• 8B61.0Infantile spinal muscular atrophy, Type I
• 8B61.1Late infantile spinal muscular atrophy, Type II
• 8B61.2Juvenile form spinal muscular dystrophy, Type III
• 8B61.3Adult onset spinal muscular atrophy, Type IV
• 8B61.4Localised spinal muscular atrophy
• 4B4YOther specified diseases of the immune system
• 4B4ZDiseases of the immune system, unspecified

Nearby in Motor neuron diseases or related disorders

• 8B60Motor neuron disease
• 8B62Post polio progressive muscular atrophy
• 4B4YOther specified diseases of the immune system
• 4B4ZDiseases of the immune system, unspecified