Allopurinol safely and effectively optimizes tioguanine metabolites in inflammatory bowel disease patients not responding to azathioprine and mercaptopurine

BACKGROUND: Many non-responders to azathioprine or mercaptopurine (6-mercaptopurine) have high normal thiopurine methyltransferase activity and preferentially metabolize mercaptopurine to produce 6-methylmercaptopurine instead of the active 6-tioguanine (6-tioguanine) metabolites. AIM: To describe the use of allopurinol in mercaptopurine/azathioprine non-responders to deliberately shunt metabolism of mercaptopurine towards 6-tioguanine. METHODS: Fifteen thiopurine non-responders whose metabolites demonstrated preferential metabolism towards 6-methylmercaptopurine are described. Subjects were commenced on allopurinol 100 mg po daily and mercaptopurine/azathioprine was reduced to 25-50% of the original dose. Patients were followed clinically and with serial 6-tioguanine and 6-methylmercaptopurine metabolite measurements. RESULTS: After initiating allopurinol, 6-tioguanine levels increased from a mean of 185.73 +/- 17.7 to 385.4 +/- 41.5 pmol/8 x 10(8) red blood cells (P < 0.001), while 6-methylmercaptopurine decreased from a mean of 10 380 +/- 1245 to 1732 +/- 502 pmol/8 x 10(8) RBCs (P < 0.001). Allopurinol led to a decrease in white blood cell from a mean of 8.28 +/- 0.95 to 6.1 +/- 0.82 x 10(8)/L (P = 0.01). CONCLUSIONS: The addition of allopurinol to thiopurine non-responders with preferential shunting to 6-methylmercaptopurine metabolites appears to be an effective means to shift metabolism towards 6-tioguanine.     

Total knee replacement in a patient with unsuspected tabes dorsalis

Rapid and progressive ligamentous laxity following an initially successful total knee replacement is unique in the authors' experience. One case is reported due to previously unsuspected tabes dorsalis.     

Williams–Beuren syndrome: novel risk alleles in transmitting parents

Copy number variation at the 7q11.23 segmental duplications is a susceptibility factor for the Williams–Beuren syndrome deletion
Cuscó et al. (2008)
Genome Research 18 (5): 683–694. Epub 21 February 2008