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Congenital miosis(MCOR)

MedGen UID:
Concept ID:
Congenital Abnormality
Synonyms: CHROMOSOME 13q32 DELETION SYNDROME; MCOR; Microcoria, congenital; Pinhole pupils
SNOMED CT: Congenital miosis (400962005)
Modes of inheritance:
Autosomal dominant inheritance
MedGen UID:
Concept ID:
Intellectual Product
Source: Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele.
HPO: HP:0007728
Monarch Initiative: MONDO:0007989
OMIM®: 156600
Orphanet: ORPHA566


Inherited congenital microcoria, also referred to as congenital miosis, is characterized by bilateral small pupils (diameter less than 2 mm) that result from an underdevelopment of the dilator pupillae muscle of the iris (Holth and Berner, 1923; Simpson and Parsons, 1989). Iris transillumination defects are a constant feature. The pupil dilates poorly or not at all in response to topically administered mydriatic drugs. The disorder is transmitted as an autosomal dominant trait with complete penetrance and is associated with goniodysgenesis and glaucoma (Tawara and Inomata, 1983; Mazzeo et al., 1986; Toulemont et al., 1995). [from OMIM]

Clinical features

From HPO
MedGen UID:
Concept ID:
Disease or Syndrome
Glaucoma refers loss of retinal ganglion cells in a characteristic pattern of optic neuropathy usually associated with increased intraocular pressure.
MedGen UID:
Concept ID:
Disease or Syndrome
Abnormal (non-physiological) constriction of the pupil.
MedGen UID:
Concept ID:
Disease or Syndrome
Nearsightedness, also known as myopia, is an eye condition that causes blurry distance vision. People who are nearsighted have more trouble seeing things that are far away (such as when driving) than things that are close up (such as when reading or using a computer). If it is not treated with corrective lenses or surgery, nearsightedness can lead to squinting, eyestrain, headaches, and significant visual impairment.\n\nNearsightedness usually begins in childhood or adolescence. It tends to worsen with age until adulthood, when it may stop getting worse (stabilize). In some people, nearsightedness improves in later adulthood.\n\nFor normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. People who are nearsighted typically have eyeballs that are too long from front to back. As a result, light entering the eye is focused too far forward, in front of the retina instead of on its surface. It is this change that causes distant objects to appear blurry. The longer the eyeball is, the farther forward light rays will be focused and the more severely nearsighted a person will be.\n\nNearsightedness is measured by how powerful a lens must be to correct it. The standard unit of lens power is called a diopter. Negative (minus) powered lenses are used to correct nearsightedness. The more severe a person's nearsightedness, the larger the number of diopters required for correction. In an individual with nearsightedness, one eye may be more nearsighted than the other.\n\nEye doctors often refer to nearsightedness less than -5 or -6 diopters as "common myopia." Nearsightedness of -6 diopters or more is commonly called "high myopia." This distinction is important because high myopia increases a person's risk of developing other eye problems that can lead to permanent vision loss or blindness. These problems include tearing and detachment of the retina, clouding of the lens (cataract), and an eye disease called glaucoma that is usually related to increased pressure within the eye. The risk of these other eye problems increases with the severity of the nearsightedness. The term "pathological myopia" is used to describe cases in which high myopia leads to tissue damage within the eye.
Raised intraocular pressure
MedGen UID:
Concept ID:
Intraocular pressure that is 2 standard deviations above the population mean.
Hypoplasia of the iris dilator muscle
MedGen UID:
Concept ID:
Congenital Abnormality
Underdevelopment of the dilatator pupillae.
MedGen UID:
Concept ID:
Anatomical Abnormality
A small pupil (typically diameter less than 2 mm) that dilates poorly or not at all in response to topically administered mydriatic drugs.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
  • CROGVCongenital miosis
Follow this link to review classifications for Congenital miosis in Orphanet.

Conditions with this feature

Spastic ataxia 7
MedGen UID:
Concept ID:
Disease or Syndrome
A rare hereditary ataxia with characteristics of an apparently non-progressive or slowly progressive symmetrical ataxia of gait, pyramidal signs in the limbs, spasticity and hyperreflexia (especially in the lower limbs) together with dysarthria and impaired pupillary reaction to light, presenting as a fixed miosis. Nystagmus may also be present.

Recent clinical studies


Cappuccio G, Brunetti-Pierri N, Clift P, Learn C, Dykes JC, Mercer CL, Callewaert B, Meerschaut I, Spinelli AM, Bruno I, Gillespie MJ, Dorfman AT, Grimberg A, Lindsay ME, Lin AE
Am J Med Genet A 2022 May;188(5):1384-1395. Epub 2022 Jan 13 doi: 10.1002/ajmg.a.62645. PMID: 35025139
Angée C, Nedelec B, Erjavec E, Rozet JM, Fares Taie L
Genes (Basel) 2021 Apr 22;12(5) doi: 10.3390/genes12050624. PMID: 33922078Free PMC Article
Meire FM, Delleman JW
Ophthalmic Paediatr Genet 1992 Jun;13(2):123-9. doi: 10.3109/13816819209087612. PMID: 1495762

Clinical prediction guides

Meire FM, Delleman JW
Ophthalmic Paediatr Genet 1992 Jun;13(2):123-9. doi: 10.3109/13816819209087612. PMID: 1495762

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