HETEROGENEITY IN ADENYLOSUCCINASE DEFICIENCY

Abstract

Adenylosuccinase deficiency was suspected in 3 mentally retarded, autistic children by the discovery of succinyladenosine and succinylaminoimidazole carboxamide riboside in their body fluids and confirmed by the finding of a deficient enzyme activity in the kidney and in the liver of patient A. (Jaeken and Van den Berghe. Lancet 2 : 1058, 1984). In patients B and C (brother and sister) follow-up showed a slowing of weight gain and, to a lesser degree, of length growth. In patient B, weight and length at the age of 3 9/12 y were at the 3rd percentile but at the age of 5 3/12 y they were 2 kg and 7 cm respectively below the 3rd percentile. In patient C, weight and length at the age of 1 6/32 y were at the 25th and at the 75th percentiles respectively, while at the age of 3 6/12 y weight was 1.5 kg below the 3rd percentile and length at the 25th percentile. Serum muscle enzymes, electromyography, nerve conduction velocity and muscle histology were normal in both patients. Patient A, in contrast, had a normal weight gain and growth. Adenylosuccinase activity (nmol/min mg protein vs means ± SEM in 8 controls) was deficient in skeletal muscle of patients B and C (0.18 and 0.66 vs 2.61 ± 0.34) but normal in patient A. No abnormalities of muscle nucleotide profiles could be detected. Conclusion: these findings indicate clinical and biochemical heterogeneity in adenylosuccinase deficiency. The presence of this deficiency in skeletal muscle of patients B and C only, suggests a causal relationship between this defect and their muscular wasting.