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- ADSL, adenylosuccinate lyase
- EEG, electroencephalogram
- HMCS, human molybdenum cofactor sulphurase
- MRI, magnetic resonance imaging
Hereditary xanthinuria, a defect of purine metabolism, results from a genetic deficiency of xanthine oxidoreductase (XOR type I; OMIM #278300), or both XOR and aldehyde oxidase deficiency (type II; OMIM #603592). The human gene encoding for XOR is located at chromosome position 2p22, while that encoding aldehyde oxidase is at 2q33.1 The cause of type I hereditary xanthinuria clearly seems to be a mutation or mutations in the XOR gene. In type II deficiency, mutations in the genes coding for both XOR and aldehyde oxidase are unlikely, because these genes are located far apart, albeit both on chromosome 2.1 The human molybdenum cofactor sulphurase (HMCS) gene, encoding an enzyme for sulphuration of the desulpho molybdenum cofactor of XOR and aldehyde oxidase, has been found mutated in two independent patients with classical xanthinuria type II.2 Both types of hereditary xanthinuria are clinically similar, but whereas patients with type I can metabolise allopurinol, those with type II cannot.1 Both types are characterised by plasma uric acid concentrations below 5 μmol/l and plasma xanthine concentrations over 10 μmol/l. Urinary excretion of uric acid is low or undetectable, and that of xanthine is elevated. Less than half the affected people have symptoms, which are caused by deposition of xanthine in the urinary tract. This results in haematuria or renal colic, and rarely, in acute renal failure or chronic complications related to urolithiasis. Muscle pains caused by xanthine deposition occur in a minority of cases.1 To the best of our knowledge, associations of hereditary xanthinuria with mental delay and autism have never been described. We report here a case of a child with hereditary xanthinuria type II with mental delay and autism, cortical renal cysts, osteopenia, hair and teeth defects, and a range of behavioural symptoms.
CASE REPORT
The proband was an …