New insights into septo-optic dysplasia.

Septo-Optic Dysplasia (SOD) is a rare disorder with postulated genetic and environmental etiology. Whilst initially considered as a very rare disease (defined as incidence of approx. 1 in 50,000 births) recent data gave a reported incidence of 1 in 10,000, with equal sex distribution. The diagnosis of SOD is predominantly a clinical one, and made with the presence of two or more features of the classic triad: 1) hypopituitarism, 2) optic nerve hypoplasia, and 3) midline brain defects, typically absence or hypoplasia of the septum pellucidum and/or corpus callosum. Hypopituitarism ranges from isolated to multiple hormone deficits, with diabetes insipidus in a minority. The condition is heterogeneous and may also manifest additional brain defects. Although homozygous mutations in the homeobox gene HESX1 have been identified in SOD, these are uncommon and genetic diagnosis can be made in only <1% of patients with autosomal recessive inheritance. Autosomal dominant inheritance has also been reported. SOX2, SOX3 and OTX2 mutations have also been identified in some forms of SOD. The aetiology of SOD is uncertain but viral infections, environmental teratogens and vascular or degenerative damage have been postulated to account for its sporadic occurrence. Other factors (endogenous or exogenous) include parental age, parity, smoking, alcohol and substance abuse, antenatal bleeding, and ethnicity. Cocaine abuse during pregnancy, which is a potent vasoconstrictor has recently been identified as a potential external cause. The phenotype of SOD is highly variable; the clinical picture may include visual impairment, short stature, obesity and sleep-wake inversion. Approximately 75-80% of patients exhibit optic nerve hypoplasia, which may be the first presenting feature. Pituitary insufficiency may evolve over time, and children with possible SOD must be kept under careful endocrine follow-up. Untreated hormonal abnormalities will further jeopardize neurodevelopment of children with SOD and could also lead to life-threatening adrenal crises. The attention should be focussed on early diagnosis and treatment and education of paediatricians how to recognize this complex disorder.