Which mechanism accounts for more than 90% of gout cases?

• A. Increased intake of purines (ETOH)
• B. Overproduction of purines
• C. Under-excretion of uric acid
• D. Both overproduction and underexcretion

Answer: (C)

The main concept is that most gout cases arise from underexcretion of uric acid by the kidneys rather than from making too much. Purines are metabolized to uric acid, which is filtered and then secreted and reabsorbed in the renal tubules before being excreted. When the kidneys don’t clear uric acid efficiently, its level in the blood rises and monosodium urate crystals can form in joints, triggering gout. This underexcretion issue accounts for the vast majority of cases—over 90%—making it the dominant mechanism.

Dietary purine load or alcohol can raise uric acid, but they are usually contributors or triggers rather than the primary cause for most people. A smaller proportion of patients have overproduction of uric acid, due to increased purine synthesis or specific metabolic defects, which explains the minority. So, the reason underexcretion is the best answer is that it explains the predominant pathophysiology seen in the majority of gout cases.