Homozygous mutations in STAT5B, a signal transducer and activator of transcription, have been reported in only a handful of patients worldwide, all manifesting with postnatal growth retardation and occasional immunologic alterations.38 Impaired STAT5B signaling may lead to aberrant peripheral myelination through cyclin D1 overexpression and may have an effect on neuronal growth and differentiation.39 Finally, we detected a possibly causative de novo PTEN mutation in a patient with patchy motor neuropathy, focal demyelination, hamartoma-like skin lesions, and autism spectrum disorder. The gene discussed is PTEN; the disease is autism spectrum disorder.