Hypoxanthine-guanine phosphoribosyltransferase (
HPRT) deficiency is a
genetic disease of
purine metabolism resulting in
uric acid overproduction.
Allopurinol, which inhibits the
enzyme xanthine oxidase and reduces
uric acid synthesis, is widely used for the treatment of
gout and
uric acid overproduction. The aim of the study was to analyze the long-term efficacy and safety of
allopurinol in patients with
HPRT deficiency. Nineteen patients (13 with
Lesch-Nyhan syndrome and 6 with partial
HPRT deficiency) were treated with
allopurinol (mean dose, 6.4 mg/kg
body weight per day; range, 3.7-9.7 mg/kg
body weight per day) and followed up for at least 12 months (mean follow-up, 7.6 years). The efficacy of
allopurinol was evaluated by serial measurement of
purine metabolic parameters and renal function as well as by clinical manifestations. Safety was assessed by recording adverse events. Treatment with
allopurinol normalized serum
urate level in all patients and resulted in a mean reduction in serum
urate of 47%.
Allopurinol treatment was associated with a mean 74% reduction in urinary
uric acid-to-
creatinine ratio. In contrast,
allopurinol treatment increased mean
hypoxanthine and
xanthine urinary excretion rates 5.4- and 9.5-fold, respectively, compared with baseline levels. The decrease in
uric acid excretion in complete and partial
HPRT-deficient patients was not accompanied by a stoichiometric substitution of
hypoxanthine and
xanthine excretion rates.
Allopurinol-related biochemical changes were similar in patients with either complete or partial
HPRT deficiency. Renal function remained stable or improved with treatment. Three patients had
urolithiasis during
allopurinol treatment. In 2 patients,
xanthine stones were documented and they required
allopurinol dose adjustments aimed at reducing excessive oxypurine excretion rates. No
allopurinol hypersensitivity reactions occurred.
Neurologic manifestations were not influenced by
allopurinol therapy. In conclusion,
allopurinol is efficacious and generally safe for the treatment of
uric acid overproduction in patients with
HPRT deficiencies.
Xanthine lithiasis, developing as a consequence of
allopurinol therapy, should be preventable by adjustment of
allopurinol dose.