X-linked spinal muscular atrophy type 2

This article is about a neuromuscular disorder of boys caused by a genetic defect in the UBA1 gene. For other conditions with similar name, see Spinal muscular atrophies.

X-linked spinal muscular atrophy type 2
Classification and external resources
Specialty
OMIM	301830
Patient UK	X-linked spinal muscular atrophy type 2

X-linked spinal muscular atrophy type 2 (SMAX2, XLSMA), also known as arthrogryposis multiplex congenita X-linked type 1 (AMCX1), is a rare neurological disorder involving death of motor neurons in the anterior horn of spinal cord resulting in generalised muscle wasting (atrophy). The disease is caused by a mutation in UBA1 gene and is passed in a X-linked recessive manner by carrier mothers to affected sons.

Affected babies have general muscle weakness, weak cry and floppy limbs; consequently, the condition is usually apparent at or even before birth. Symptoms resemble the more severe forms of the more common spinal muscular atrophy (SMA); however, SMAX2 is caused by a different genetic defect and only genetic testing can correctly identify the disease.

The disorder is usually fatal in infancy or early childhood due to progressive respiratory failure, although survival into teenage years have been reported. As with many genetic disorders, there is no known cure to SMAX2. Appropriate palliative care may be able to increase quality of life and extend lifespan.

See also

• Spinal muscular atrophies
• Arthrogryposis

Further reading

• Baumbach-Reardon L.; Sacharow S.; Ahearn M. E. "Spinal Muscular Atrophy, X-Linked Infantile." 30 Oct 2008 [Updated 13 Sep 2012]. In: Pagon R. A.; Adam M. P.; Ardinger H. H.; et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2014. Available from: www.ncbi.nlm.nih.gov/books/NBK2594.