6. Deficit in glucose-6-phosphate dehydrogenase (G6PD) or history of hemolytic anemia (all patients must be tested for G6PD at the screening visit to assess for their eligibility): such patients can be enrolled directly in the second stage of the study and be randomized to receive one of the two other study drugs (azathioprine or colchicine). The number of patients enrolled directly in stage 2 of the study will be capped at 10 (10%).