Abstract
Spinal muscular atrophy (SMA) is a group of allelic autosomal recessive genetic disorders
characterized by progressive motor neuron loss, symmetrical weakness, and skeletal
muscle atrophy. It is traditionally classified as a pure lower motor neuron disorder,
for which currently definitive diagnosis is possible by molecular genetic testing.
The problem arises when an infant presents clinically like SMA but is negative for
survival motor neuron gene. A 3-month-old infant presented with paucity of limb movement
and weak cry. Clinical presentation was suggestive of spinal muscular atrophy type
I but genetic test for exon 7 deletion on survival motor neuron gene on chromosome
5 was negative. Detailed investigation revealed this a case of infantile motor axonal
neuropathy. Two years follow-up has revealed partial recovery in limb movements and
of bulbar function. There is paucity in neurology literature of such cases and the
importance of genetic studies is hence emphasized.
Keywords
Spinal muscular atrophy - SMA variant - SMN gene - infantile neuropathies - floppy
infant
