Kugelberg Welander Spinal Muscular Atrophy

Spinal muscular atrophies (SMAs) represent a rare group of inherited disorders that cause progressive degeneration of the anterior horn cells of the spinal cord. The exact cause of the degeneration is unknown. Loss of these cells results in a progressive lower motor neuron disease that has no sensory involvement and that is manifested as hypotonia, weakness, and progressive paralysis. Kugelberg Welander spinal muscular atrophy (also known as Wohlfart-Kugelberg-Welander syndrome or mild SMA) is a milder form of SMA, with symptoms typically presenting after age 18 months.^{[1, 2, 3]}
SMAs were first described in the 1890s, by Guido Werdnig, a physician from the University of Vienna, in his lecture "On a Case of Muscular Dystrophy with Positive Spinal Cord Findings." Soon after, Professor Johann Hoffmann from Heidelberg University presented a paper describing a syndrome of progressive atrophy, weakness, and death during the early childhood period of siblings with genetically normal parents. Both physicians conducted autopsies on their patients and found severe atrophy of the ventral roots of the spinal cord. They also found histologic evidence of loss of motor neurons in the anterior horn cells of this region. Hoffmann called the syndrome spinale muskelatrophie (spinal muscular atrophy).
In the early 1960s, Byers and Banker classified SMA into categories based on the severity and age of onset of the symptoms, in an effort to predict prognosis. Their system, summarized below, became the basis for the most widely recognized system now used for the classification of SMA.