Orphanet: Micro syndrome

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Micro syndrome

Disease definition

Micro syndrome is an autosomal recessive disorder caracterised by ocular and neurodevelopmental defects and by microgenitalia. It presents with severe intellectual disability, microcephaly, congenital cataract, microcornea, microphthalmia, agenesis/hypoplasia of the corpus callosum, and hypogenitalism.

Summary

Epidemiology

Since its initial description, 26 cases of Micro syndrome have been reported in the literature.

Clinical description

With exception of the ophthalmologic features, the clinical and dysmorphic findings are either unapparent or subtle in the early postnatal period.

Etiology

Mutations in RAB3GAP, a gene showing linkage to a region of homozygosity at 2q21.3, have been identified in some families. The RAB3GAP gene encodes a member of the Rab3 protein family, which is involved in regulated exocytosis of neurotransmitters and hormones. It has been suggested that the hypogenitalism is hypothalamic in origin, and that the ocular and neurodevelopmental defects result from abnormal neurotransmitter vesicular transport and exocytosis.

Diagnostic methods

Ocular findings are the most reliable diagnostic signs of Micro syndrome, especially during infancy. Pathognomonic ophthalmologic findings include microphthalmia, microcornea, cataract, atonic pupils, mild optic atrophy, and severe cortical vision impairment.

Differential diagnosis

Micro syndrome should be considered in any infant with congenital cataract.

Management and treatment

There is no specific treatment for Micro syndrome and the management is symptomatic. The conventional approach used for congenital cataract should be recommended.

Expert reviewer(s): Dr Pinar AGRAS - Dr Murat DERBENT - Last update: January 2006

A summary on this disease is available in Deutsch (2006) Español (2006) Français (2006) Italiano (2006) Nederlands (2006)

Detailed information

Guidelines

Clinical practice guidelines
Deutsch (2019) - AWMF
Français (2022) - PNDS

Disease review articles

Review article
English (2006, pdf) - Orphanet

Clinical genetics review
English (2018) - GeneReviews

Genetic Testing

Guidance for genetic testing
English (2020) - Eur J Hum Genet

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