TBC1D20 gene

• Overview
• Congenital cataracts
• Microphthalmia, anophthalmia, coloboma (MAC)
• References

Overview

Gene (OMIM No.)	TBC1D20 (#611663)
Function of gene/protein	Protein: TBC1 domain family member 20 Regulates the activity of GTPases such as RAB18 and RAB1 RAB18 is involved in intracellular vesicle trafficking, structural organization and cell autophagy RAB1 maintains the structure of Golgi apparatus
Clinical phenotype (OMIM phenotype no.)	Warburg micro syndrome 4 (#615663)
Inheritance	Autosomal recessive
Ocular features	Bilateral congenital cataracts Microphthalmia, anophthalmia, coloboma (MAC) spectrum Microcornea Atonic pupils Optic atrophy Cortical visual impairment
Systemic features	Structural abnormalities of the brain (postnatal microcephaly, polymicrogyria, corpus callosum hypogenesis, cerebellar vermis hypoplasia) Seizures Facial anomalies (wide nasal bridge, relatively narrow mouth and prominent subnasal region) Limb hypotonia in infancy progressing to spastic quadriplegia later in life Hypothalamic hypogonadism (micropenis and cryptorchidismin in boys; hypoplastic labia minora and clitorial hypoplasia in girls) Severe developmental delays
Key investigations	B-scan USS to measure axial length to document microphthalmia and detect any posterior segment abnormalities Electrophysiology TORCH screen for children with congenital cataract MRI brain and orbit Systemic assessment with a paediatrician and other relevant specialists
Molecular diagnosis	Next generation sequencing Targeted gene panels (MAC, cataract and/or optic atrophy) Whole genome sequencing
Management	Ocular Management of MAC Management of congenital cataract Systemic Multidisciplinary approach
Therapies under research	None at present
Further information	Medline Plus

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References

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