Proximal spinal muscular atrophy

Abstract

Five sibs, 4 brothers and 1 sister, aged 14 to 32 yr, had an early onset of proximal muscle weakness, affecting pelvic girdles before shoulder girdles. The presence of fasciculations in 3 of the 5, the electromyographic findings (reduced interference pattern in 3 patients, fibrillations, positive waves, and giant motor unit potentials in one) and the changes in muscle biopsies indicative of neurogenic atrophy, all provide evidence that the illness in these 5 sibs is that of spinal muscular atrophy. The gynecomastia in the 2 younger boys is thought to be pubertal in origin. Three forms of infantile proximal spinal muscular atrophy are now recognized, and are all inherited as autosomal recessives. The first of these is severe and progressive; Werdnig Hoffmann disease, with onset almost always by 3 mth of age and death by 4 yr. There is a more benign form, with onset of generalized muscle weakness between 3 and 9 mth and survival into late childhood and even adult life with severe handicap and skeletal abnormalities. Two such affected brothers are described. Thirdly, there is a form with onset around 12 mth, when the child first attempts to walk. Initially weakness is localized to the pelvic girdle at the outset, preceding shoulder girdle weakness by several yr. Such patients usually survive into adult life, perhaps in a wheel chair but without skeletal abnormalities of the second type. Sometimes they have little physical disability. These patients are often considered as having 'Kugelberg Welander disease'. The authors consider that the 5 patients described fall into this category. It is interesting that the illness in the affected sibs, after an initial rapid progression is now almost stationary.