Bruising and the ketogenic diet: evidence for diet-induced changes in platelet function.

Excessive bruising is a symptom noted by parents of some children treated with the ketogenic diet for epilepsy control, although this side effect is not reported in the literature. We evaluated our cohort of current and past diet-treated patients for symptoms of bruising or bleeding through chart review and prospective screening at clinic follow-up visits. A significant increase in bruising or other minor bleeding was reported and/or observed in 16 of 51 patients (31.4%). There were no differences in sex distribution or number of anticonvulsants used between patients with bruising/bleeding and those without this symptom, although the group with bruising/bleeding was significantly younger. No specific anticonvulsant was associated with bruising/bleeding. Six patients with diet-induced bruising/bleeding underwent an investigation for bleeding diathesis. Five of these patients had prolonged bleeding times and all had diminished responsiveness to various platelet aggregating agents, with no evidence of a release defect. The abnormalities all normalized in the 1 patient tested after ceasing the diet. No patients had serious hemorrhage. One patient had mild von Willebrand disease, which had been asymptomatic before diet initiation. Some patients were Stimate responsive, suggesting a treatment for more severe bouts of symptoms. These data suggest that a ketogenic diet-related bleeding tendency occurs in about one third of treated patients owing to preexisting factors defining susceptibility in combination with diet-induced depression of platelet responsiveness, possibly related to changes in platelet membrane lipid composition and/or concentration and resultant effects on function of membrane-embedded proteins. Patients on the diet undergoing anticoagulation or surgery should be evaluated carefully for symptoms of bleeding tendency.