Rare Ophthalmology News

Disease Profile

Microphthalmia

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

Unknown

Age of onset

Antenatal

ICD-10

Q11.0 Q11.1 Q11.2

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

Isolated anophthalmia microphthalmia; Isolated pure microphthalmia; Isolated anophthalmia-microphthalmia syndrome;

Summary

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.
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Orpha Number: 2542

Definition
A non-syndromic group of structural developmental eye defects characterized by the variable combination of microphthalmia, ocular coloboma, and anophthalmia, either unilaterally or bilaterally, with no other associated ocular conditions in the affected/contralateral eye, and no systemic anomalies.

Epidemiology
The prevalence of microphthalmia is 1:7,000, anophthalmia is 1:30,000 and coloboma is 1:5,000 live births, with combined prevalence 3-30:100,000 births. Associated malformations affect 32-93% of the patients. There is no clear predilection for ethnicity or gender.

Clinical description
Microphthalmia-anophthalmia-coloboma (MAC) consists of phenotypic continuum of congenital eye defects that are manifest at birth. In some cases, such as retinal coloboma or mild microphthalmia, detection may occur later in life. True anophthalmia is the abortion of eye development at the developing optic vesicle stage (3-4 weeks gestation) leading to absence of the eye, optic nerve and chiasm. Commonly clinical anophthalmia (also referred to as severe microphthalmia) occurs, where a small cystic remnant is detectable on pathology/imaging. Nanophthalmos and posterior microphthalmia, are rare subsets of microphthalmia, where overall the eye is structurally normal but it has a reduced axial length of <20 mm with high hypermetropia. Ocular coloboma may involve the inferonasal aspect of the eye, including the iris, ciliary body, zonules, retina, retinal pigment epithelium (RPE), choroid and/or optic disc.

Etiology
MAC has a complex etiology, with monogenic, chromosomal and environmental causes. SOX2, OTX2 and STRA6 variants account for 75% of bilateral anophthalmia/severe microphthalmia. Chromosomal abnormalities account for 20-30% of MAC. Environmental factors associated with anophthalmia include maternally-acquired infections, smoking and perinatal exposure to certain medications. Maternal vitamin A deficiency, alcohol abuse and use of teratogenic drugs during pregnancy have been linked to coloboma and microphthalmia.

Diagnostic methods
Postnatal diagnosis can be made through clinical examination, with confirmation of true/clinical anophthalmia through MRI brain and orbit imaging. Molecular diagnosis can be made through genetic testing, such as array comparative genomic hybridization (aCGH) or whole exome/genome sequencing.

Differential diagnosis
Differential diagnoses includes aniridia, anterior segment dysgenesis, congenital corneal opacity, sclerocornea, cryptophthalmos, cyclopia and congenital cystic eye. MAC may also occur as part of various syndromes, and thus examination by specialists for the presence of systemic features (e.g. associated neurological or pituitary defects) is recommended. Genetic diagnosis may aid the identification of potential systemic anomalies.

Antenatal diagnosis
Prenatal diagnosis of anophthalmia or microphthalmia may be made through 2D or 3D ultrasonography during the second trimester (or 12 weeks post-conception with a transvaginal ultrasound) or fetal magnetic resonance imaging to visualize the orbit.

Genetic counseling
Genetic counselling can be challenging due to the range of known genetic causes and phenotypic variability. Prediction of inheritance pattern is often difficult, due to de novo changes, mosaicism and non-penetrance. If a genetic diagnosis is established, informed family planning advice can be provided including prenatal and preimplantation diagnosis.

Management and treatment
There is no treatment for MAC patients. They should be managed by a multidisciplinary team of specialists, including ophthalmologists, pediatricians and clinical geneticists. If there is visual potential, children should be monitored to maximize vision by correcting refractive error or squints, and preventing amblyopia. Fundus examinations are required in patients with chorioretinal coloboma as it is associated with a risk of retinal detachment. Low vision should be supported using visual aids. Significant microphthalmic or anophthalmic eyes may undergo socket expansion using enlarging cosmetic shells/conformers to minimize facial deformity.

Prognosis
Isolated MAC are structural birth defects with no treatment available.

Visit the Orphanet disease page for more resources.

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • Genetics Home Reference (GHR) contains information on Microphthalmia. This website is maintained by the National Library of Medicine.
  • The National Eye Institute (NEI) was established by Congress in 1968 to protect and prolong the vision of the American people. Click on the link to view information on this topic.

In-Depth Information

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Microphthalmia. Click on the link to view a sample search on this topic.