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At a glance

It is a rare genetic medical condition characterized by a triad of optic nerve hypoplasia, structural brain abnormalities, and hypothalamic/pituitary deficiencies. To establish the diagnosis, two of the three features must be present. All three are only present in 30% of affected individuals. Neuroradiologically, this syndrome is defined by agenesis of the interhemispheric septum pellucidum, schizencephaly, hydranencephaly, and holoprosencephaly. Clinically, other important features include mild to severe developmental delay, seizures, visual impairment, sleep disturbance, precocious puberty, microgenitalia (especially in males), obesity, anosmia, sensorineural hearing loss, and cardiac anomalies.

Synonyms

Septo-Optic Dysplasia; Optic Nerve Hypoplasia; Dwarfism-Septo-Optic-Dysplasia.

History

This medical condition was first reported in 1941 by D. L. Reeves, an American neurologist, when he observed the association between visual impairment due to optic nerve abnormalities and the absence of the septum pellucidum. However, it was in 1956 that George de Morsier (1894-1982), a French-Swiss neurologist, called attention to the triad of findings associated with this condition. He named it septo-optic dysplasia.

Incidence

The exact incidence is established at 1:10,000 live births worldwide. It is prevalent equally in males and females. This medical condition has been linked to young maternal age, cocaine abuse, and other street drugs.

Genetic inheritance

A rare familial recurrence has been reported. It is recognized as a phenotypically variable disorder. This suggests that there is possibly one genetic form that has been linked to the homeobox HESX1 gene. A mode of inheritance has not been determined. A genetic diagnosis can currently be made in less than 1% of the patients. Sporadic mutations are most frequent and involve the OTX2, SOX2, and PAX6. In most cases, De Morsier’s Syndrome is a sporadic birth defect of unknown cause and does not recur with subsequent pregnancies.

Pathophysiology

It is a developmental disorder resulting from a defect of normal embryological development. There is no single cause to explain this medical condition. The typical picture includes optic hypoplasia, pituitary hypofunction, and midline defects of the prosencephalon. Milder forms exist in individuals with heterozygous mutations of the gene.

Diagnosis

Clinical picture, family history, brain imaging and MRI, and cytogenetic identification of mutations of the HESX1 gene.

Clinical aspects

Wide variability in the clinical picture. The syndrome is characterized by hypoplasia of the optic disk and nerve, hypothalamic–pituitary axis defects, and agenesis of the septum pellucidum. Visual impairment is usually noted at birth, ranging from decreased vision in one eye to no vision in both eyes secondary to optic disc hypoplasia/atrophy and corneal opacification. Variable pupillary dilatation is often associated with this nystagmus. Optic nerve hypoplasia is generally manifested with nystagmus and a variable degree of visual impairment, ie, ranging from normal vision to complete blindness. ...

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