Atlantoaxial subluxation with recurrent consciousness disturbance in a boy with Lesch-Nyhan syndrome.

UNLABELLED: Deficiency of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) may cause various clinical entities such as Lesch-Nyhan syndrome (LNS). A 9.5-y-old boy with the phenotypic features of LNS, including hyperuricaemia, choreoathetosis, self-mutilation and profound neurological dysfunction, was found to have HPRT deficiency. Normocytic anaemia, hyperuricaemia (uric acid 594.8 micromol/l) and microscopic haematuria with uric acid crystals were noted. Ultrasonography showed bilateral nephrocalcinosis and urinary bladder stones. In addition, he presented with three episodes of consciousness disturbance with limb paresis, possibly caused by atlantoaxial subluxation (AAS) with compression myelopathy. The diagnosis was made by the amount of residual enzyme activity and a single nucleotide substitution on the acceptor site region of intron 5 (IVS5-1 G-->C) of the HPRT gene, inherited from his asymptomatic mother.

CONCLUSION: Lesch-Nyhan syndrome is a devastating sex-linked recessive disorder resulting from almost complete deficiency of the activity of HPRT. This report highlights the unusual AAS in a boy with LNS presenting recurrent consciousness change. The mutation described herein is a hitherto unreported splicing error leading to exon 6 skipping of the HPRT gene.