Mutations in MICOS13 (aka QIL1) cause severe infantile mitochondrial disease characterised by failure to thrive, microcephaly, truncal hypotonia, spasticity and cerebellar atrophy, lactic acidosis and 3-methylglutoconic aciduria (3-MGA) [242,243,244]. The gene discussed is MICOS13; the disease is Cerebellar atrophy.