The suspicion that patients actually had HSD10 mitochondrial disease prompted us to exclude two brothers from this study, who have been reported as beta-ketothiolase deficient by Jänisch et al. 1993 and Hesse et al. 2004 [25, 26], but in whom we consider published clinical and enzyme data rather nonsuggestive for MATD. The gene discussed is FSIP1; the disease is mitochondrial disease.