84. A 50-year-old man presents with recur-rent episodes of acute excruciating pain,swelling, and redness of his right great toe, all following a large meal that was accom-panied by copious consumption of alcohol. In the past, others in his family have hadsimilar symptoms. The metatarsophalangeal joint of the right great toe is erythematous,edematous, and tender. Which of the follow- ing is the most likely etiology of this condi-tion? *