Autosomal recessive mutations in the MPV17 gene cause MPV17-related hepatocerebral mitochondrial DNA depletion syndrome (MDDS), including Navajo neurohepatopathy, which typically has hepatic and gastrointestinal manifestations, metabolic derangements, and neurological involvement, including developmental delay, hypotonia, microcephaly, and motor and sensory peripheral neuropathy; most patients die by childhood4. The gene discussed is MPV17; the disease is microcephaly.