We are the first to report severely reduced amount of mitochondrial complexes (specifically I and V), but other mitochondrial defects have been reported in PIGA mutations: e.g. ‘disorganized mitochondria’ in FCC syndrome [16] and ‘abnormal ATP production’ in a patient with accelerated linear growth and obesity [17]. The gene discussed is PIGA; the disease is obesity due to melanocortin 4 receptor deficiency.