Spinal muscular atrophy is also known as or subsumes Kugelberg-Welander disease and Werdnig-Hoffman disease. -ed
Spinal muscular atrophy presents with proximal muscle weakness of the upper and lower extremities, the latter being weaker than the former, at least initially. The condition is caused by a deletion of exon 7 on chromosome 5. Other SMAs exist that are not linked to 5Q. Current classification is based on clinical criteria, including age of onset and maximum function attained. The diagnosis is established by a DNA test for the SMN gene. Further testing, including EMG and muscle biopsy are unnecessary. To date, therapeutic trials have failed to reveal a specific treatment for this condition.