Spinal Muscular Atrophy, Distal, Autosomal Recessive, 1 is a rare neuromuscular disorder characterized by weakness of the distal muscles, respiratory distress due to diaphragmatic paralysis and dysfunction of the peripheral nerves and the autonomic nervous system.
The disease can often be misdiagnosed as Spinal Muscular Atrophy (SMA), a disorder that affects proximal muscles as opposed to the distal muscle involvement seen in SMARD1. Management of the disorder includes physical and occupational therapy to maintain muscle strength, immunizations and antibiotics to prevent respiratory infections and the use of ventilators for respiratory support.
SMARD1 is an autosomal recessive disorder caused by mutations in the IGHMBP2 gene. The gene encodes a DNA/RNA helicase involved in transcription regulation. Defects in the gene affect alpha motor neurons and result in their death over time. So far more than sixty mutations have been found to be associated with the disease. These include missense, nonsense, frameshift and splice site mutations, either in the homozygous or compound heterozygous form and usually result in the loss of function of the IGHMBP2 protein.