Myoadenylate Deaminase Deficiency: An Enzyme Defect in Search of a Disease
In 1978 Fischbein et a1,1 described 5 patients with a myoadenylate deaminase (MAD) deficiency, which were detected during a histochemical screening of 250 consecutive muscle biopsies. The deficiency was confirmed by a biochemical assay of the enzyme. Clinically three of the patients complained of muscle cramping, in one case associated with postexercise fatigue. CK was only moderately elevated, the myogram showed minor abnormalities, in muscle there were histologically no or only slight alterations. These three patients didn’t show any muscle weakness or atrophy. In 1979 they,2 described 7 other patients, three of them, however, showing a quite different clinical picture with signs of collagen vascular disease. In their series of consecutive muscle biopsies they found a frequency of about 1,5% of MAD deficient biopsies. Other authors,3,4,5 described a deficiency in about 1,5–2,0% of the biopsies. Half of these biopsies came from patients with a clinical symptomatology of exercise intolerance with muscular pain and/or fatigue. The other half came from patients displaying a wide diversity of partly well defined clinical entities, among others collagen vascular disease, neuropathy, amyotrophic lateral sclerosis, dystrophy, cardioskeletal myopathy, spinal muscular atrophy, paroxysmal myoglobinuria, facio-scapulo-humeral syndrome, infantile hypotonia and so on.
KeywordsAmyotrophic Lateral Sclerosis Spinal Muscular Atrophy Exercise Intolerance Collagen Vascular Disease Enzyme Defect
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