Septooptic dysplasia (SOD)
What is it?
De Morsier syndrome, also called septooptic dysplasia (SOD) or Kaplan-Grumbach-Hoyt syndrome, is a rare genetic disorder characterized by aplasia or hypoplasia of the septum (membrane that separates the ventricles of the brain) and/or of the optic nerves, optic chiasm and / or pituitary gland and the hypothalamus. Loss of vision and malformations of the brain of varying severity, from aplasia of the olfactory system to holoprosencephaly, are also often present, often associated with mental retardation. The incidence is about 1 / 10,000 live births. Many cases of SOD are sporadic. Familial cases of mutations in the HESX1 gene (3p21.2-p21.1), both homozygous (autosomal recessive inheritance) and heterozygous (autosomal dominant inheritance), have also been described. Three other genes are implicated in some related phenotypes similar to the SOD spectrum: SOX2 mutations (3q26.3-q27) are associated with anophthalmia / macrophthalmia in addition to clinical signs of SOD; mutations / duplications of the SOX3 gene (Xq26.3) are associated with defects in the structures of the midline brain and hypopituitarism (without visual defects); OTX2 mutations (14q21-q22) are associated with hypopituitarism and hypoplasia of the anterior pituitary gland, with or without visual impairment. Mutations in these genes have been identified in less than 1% of patients. Environmental factors (alcohol and drug abuse, young maternal age) may be involved.
How is it diagnosed?
SOD can be suspected in the prenatal period using ultrasound and subsequent MRI examinations of the fetus, as well as in newborns with hypoglycemia, jaundice, micropenis (with or without cryptorchidism) and nystagmus, with or without midline abnormalities (e.g., cleft palate). Clinical diagnosis requires at least two signs of the classic triad: optic nerve hypoplasia (mono- or bilateral), pituitary hormones, and defects in the midline structures of the brain. The severity varies; only 30% of patients have the full triad and most also have other symptoms associated with visual impairment ranging from nystagmus to blindness. Hypopituitarism is present in 62-80% of cases, and growth hormone deficiency is the most common endocrinological abnormality. Defects in the midline structures of the brain include agenesis of the septum (60% of cases) and / or corpus callosum. Cortical malformations (sometimes called SOD plus syndrome) have also been described. Other clinical signs include diabetes insipidus, sleep disorders, autism, premature puberty, obesity, thermoregulatory disorders, anosmia, sensorineural hearing loss, heart disease, finger abnormalities, microphthalmia, and coloboma. The diagnosis can be confirmed by ophthalmologic examination, MRI and dynamic tests of pituitary function.
How is it treated?
Treatment is symptomatic and interdisciplinary with regular follow-up. Hormone deficiency is treated with hormone replacement therapy. Children can benefit from vision and other disability rehabilitation programs and occupational therapy. The prognosis is variable and depends on the severity of the disease. Early diagnosis contributes to a better prognosis, as it allows timely management of hormonal deficiency and visual impairment
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