Microphthalmia, Isolated 6

Alternative Names

  • MCOP6
  • Microphthalmia, Posterior Nonsyndromic

Associated Genes

Protease, Serine, 56
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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Congenital malformations of eye, ear, face and neck

OMIM Number

613517

Mode of Inheritance

Autosomal recessive

Gene Map Locus

2q37.1

Description

Microphthalmia is a congenital disorder that results in one or both eyeballs being abnormally small.  It is characterized by a shortened axial length (in the range of 14 to 20 mm) that causes extreme hyperopia (+7.5 to +21 D).  Other ocular features include normal anterior segments, elevated papillomacular retinal folds, steep corneal curvatures, shallow anterior chambers and thickened scleral walls.  The disorder results in mild to moderate vision loss.  Several genetically distinct forms of isolated microphthalmia have been reported.  MCOP6 is a specific form of microphthalmia caused by mutations in the PRSS56 gene. 

Diagnosis can be made in-utero based on scans and genetic tests while postnatal diagnosis is made based on ocular examinations.  Microphthalmia results in mildly to moderately reduced visual acuity.  Hence treatment is focused on improving vision with corrective lenses.  Children may require conformers, which are plastic structures that help the eye socket and facial bones develop properly. Patching of the better eye has also been found to improve vision in the weak eye.  Surgical intervention may be required in certain cases, such as in the development of cataracts. 

Molecular Genetics

Microphthalmia, isolated 6 is an autosomal recessive disorder, that is caused by mutations in the PRSS56 gene. This gene encodes a serine protease believed to play an important role in camera-type eye development.  More than a dozen PRSS56 mutations, both homozygous and compound heterozygous, have been linked to MCOP6.

Epidemiology in the Arab World

View Map
Subject IDCountrySexFamily HistoryParental ConsanguinityHPO TermsVariantZygosityMode of InheritanceReferenceRemarks
613517.1Saudi ArabiaMaleNo High hypermetropia; MicrophthalmiaNM_001195129.2:c.1066dupHomozygousAutosomal, RecessiveNowilaty et al. 2013; Aldahmesh et al. 2011
613517.2Saudi ArabiaMaleNo High hypermetropia; MicrophthalmiaNM_001195129.2:c.1066dupHomozygousAutosomal, RecessiveNowilaty et al. 2013; Aldahmesh et al. 2011 Affected parents
613517.3Saudi ArabiaMaleNo High hypermetropia; MicrophthalmiaNM_001195129.2:c.1066dupHomozygousAutosomal, RecessiveNowilaty et al. 2013; Aldahmesh et al. 2011
613517.G.1Saudi ArabiaYes High hypermetropia; MicrophthalmiaNM_001195129.2:c.1555G>AHomozygousAutosomal, RecessiveNowilaty et al. 2013; Aldahmesh et al. 2011 5 affected siblings
613517.G.2Saudi ArabiaNo High hypermetropia; MicrophthalmiaNM_001195129.2:c.1066dupHomozygousAutosomal, RecessiveNowilaty et al. 2013; Aldahmesh et al. 2011 3 affected siblings
613517.G.3Saudi ArabiaNo High hypermetropia; MicrophthalmiaNM_001195129.2:c.1066dupHomozygousAutosomal, RecessiveNowilaty et al. 2013; Aldahmesh et al. 2011 4 affected siblings
613517.G.4Saudi ArabiaNo High hypermetropia; MicrophthalmiaNM_001195129.2:c.1066dupHomozygousAutosomal, RecessiveNowilaty et al. 2013; Aldahmesh et al. 2011 2 affected siblings
613517.G.5Saudi ArabiaNo High hypermetropia; MicrophthalmiaNM_001195129.2:c.1601T>GHomozygousAutosomal, RecessiveNowilaty et al. 2013; Aldahmesh et al. 2011; Patel et al. 2018 2 affected siblings

Other Reports

Saudi Arabia

Nowilaty et al. (2013) reported on 24 posterior microphthalmos affected patients, ranging in age from 2 to 47 years.  The patients belonged to 12 Saudi families, seven of which were consanguineous.  They were all found to have high hyperopia ³8 D, normal anterior segments, axial length <20 mm (mean 16.25 mm), foreshortening of the posterior chamber and characteristic retinal papillomacular folds/wrinkles.  Mean cycloplegic refraction for the right eye was +15.09 D.  While axial length was positively correlated with corneal diameter, it showed an inverse relationship with corneal power (mean 48.89 D).  Genetic analysis of the patients revealed homozygous PRSS56 mutations in 19 individuals.  The authors noted that there were no clinical differences between patients carrying MFRP mutations, PRSS56 mutations or no detected mutation. However, patients with the PRSS56 truncating mutation had shorter mean axial length (15.72 mm) compared to patients with PRSS56 missense mutations (16.37 mm).  They also displayed higher mean corneal power (49.63 D vs. 48.37 D), smaller mean corneal diameter (11.12 mm vs. 11.69 mm) and higher mean hyperopia (+16.42 D vs. +14.55 D). 

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