engleski

Two cases of hypoxantine-guanine phosphoribosyl transferase deficiency in a family

In September 1994, an eleven-year-old, mentaly and physically retarded boy (O.G.) was admitted to the children,s ward of the Ptuj General Hospital. The boy came from the Nursing Home for mentally retarded children in Domava. Severe acute infection of the urinary tract was diagnosed on admission. Numerous injuries of the fingers and the lips caused by self-destructive behaviour were also observed. The routine laboratory investigation showed many abnormalities: highly pathological inflammatory haemathologic tests, a positive urine specimen for bacterial culture, high urea (20.9 mmol/l) and a high creatinine value (194 umol/l). The patient,s plasma uric acid was extremely high (1435 umol/l) and so was the 24-hour urinary excretion of uric acid (13.5 mmol/l). The ultra sound examination disclosed bilateral nephrolitiasis. The pathological laboratory tests and the clinical manifestation suggested the inborn error of uric acid metabolism (Lesch-Nychan syndrome). For the purpose of genetic counselling of the patient,s sister (O.S.) who is physically and mentally healthy and was abour to start her own family, it was necessary to determine the hypoxantine-guanine phosophoribosyl transferase (HGPRT) activity. The lack of this enzyme was supposed to be the most probable cause of the patient,s condition. The boy,s nephew B.R. is also mentally and physically retarded (his mother - our patient O.G.,s sister - had dies earlier of unknown cause). HGPRT activity in lysed erythrocytes, measured with a modification of the method of Seegmiller et al. was found to be the following: O.G. = 12.72 nmol IMP/mg Hb/h B.R. = 41.25 nmol IMP/mg Hb/h O.S. = 88.51 nmol IMP/mg Hb/h Normal controls = 83.6+ 14.5 nmol IMP/mg Hb/h The extreme deficiency of HGPRT activity in the patient O.H. was found to be the cause of hyperuricosuria and severe mental retardation combined with self-destructive behaviour. In the patient,s nephew (B.R.), the deficiency of the same enzyme was less expressed. The patient,s sister (O.S.) has normal HGPRT activity, which suggests that her X chromosome is not mutated. It is to be expected that her male offspring will not be affected by HGPRT deficiency.

hypoxantine-guanine phosphoribosyl transferase

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