A mutation in the gene APOO, encoding for MIC26 (p.I117T), was recently identified in a patient with a complex phenotype (including progressive developmental delay, lactic acidosis, muscle weakness, hypotonia, weight loss, gastrointestinal and body temperature dysautonomia, repetitive infections, cognitive impairment and autistic behaviour [112] (Table 1). The gene discussed is APOO; the disease is Global developmental delay.