Distal spinal muscular atrophy type 2 (DSMA2), also known as Jerash type distal hereditary motor neuropathy (HMNJ), is a very rare childhood-onset genetic disorder characterised by progressive muscle wasting affecting lower and subsequently upper limbs. The disorder has been described in Arab inhabitants of Jerash region in Jordan[1][2] as well as in a Chinese family.[3]
The condition is linked to a genetic mutation in the SIGMAR1 gene on chromosome 19 (locus 19p13.3) and is likely inherited in an autosomal recessive manner.[3]