What is Spinal Muscular Atrophy with Respiratory Distress?
Spinal Muscular Atrophy with Respiratory Distress Type 1 (SMARD1) is a neuromuscular condition causing weakness of the muscles. It is the second anterior horn cell disease in infants in which the genetic defect has been defined. SMARD1 is not linked to the SMN1 gene locus on chromosome 5q13 (classic SMA), but is caused by mutations in the IGHMBP2 gene on chromosome 11q13. Despite a substantial overlap in clinical features, the phenotypes of SMA versus SMARD1 can be distinguished.
In SMARD1, the predominating symptom is a severe respiratory distress due to a paralysis of the diaphragm. Most patients present [show symptoms] at the age of 1 to 6 months with respiratory failure and progressive muscle weakness with predominantly distal lower limb muscle involvement. Sensory and autonomic nervous systems may also be involved.
Early involvement of the diaphragm and predominance of distal muscle weakness clearly distinguishes SMARD1 from Type 1 SMA. Essentially, in SMA1, symptoms manifest in reverse order. Infants with SMA1 will become floppy due to weakness of the proximal limb muscles and assume a frog leg position before they suffer from respiratory failure. In contrast to SMARD1, SMA1 infants have intercostal recessions and develop inefficient respiration due to paralysis of intercostal muscles.
Is SMARD1 Hereditary?
The gene for SMARD1 is passed from parents to their children, but SMARD1 can only affect a child if both parents carry a defective gene (this is called an autosomal recessive pattern). Genes come in pairs, one from each parent. If a person has one normal and one affected gene they do not show the symptoms of SMARD1 but are carriers. If both genes are affected they will have SMARD1.
Each child of carrier parents has a 1 in 4 chance of being affected by SMA, a 2 in 4 chance of being a carrier themselves, and a 1 in 4 chance of being completely clear of SMA. Boys and girls are affected equally.
SMARD1 can be diagnosed from a blood sample and genetic counselling including prenatal diagnosis is available.
Where Can I Get More Information?
The Jennifer Trust for Spinal Muscular Atrophy
Elta House
Birmingham Road
STRATFORD upon AVON
Warwickshire,
CV37 0AQ
U.K.
Tel: +44 (0)1789 267 520
Fax: +44 (0)1789 268 371
Email:
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See Also
Please read our fact sheet on Type 1 SMA. | 
