Lithium carbonate therapy in severe Felty's syndrome. Benefits, toxicity, and granulocyte function.

Lithium carbonate was administered to six patients with severe Felty's syndrome, five of whom had problems with infection. Two patients had granulocyte increments that persisted after therapy was discontinued; in one of them problems with infections resolved. In another patient a transient granulocyte rise accompanied treatment. There was no response in three patients. Granulocyte function was measured in three patients during treatment. It was normal except for subnormal hexose monophosphate shunt activity in two patients. Although serum lithium levels were less than 1.5 mmole/L, serious toxic effect occurred in one patient and significant side effects in the other five. These results support a short trial of lithium carbonate therapy in patients with severe symptomatic Felty's syndrome. Potentially beneficial granulocyte increases occur in a minority of patients only, however, and side effects and toxic effects are common.