A rare genetic optic nerve disorder characterized by visual impairment or blindness resulting from varying degrees of underdevelopment of the optic nerve or even complete absence of the optic nerve, ganglion cells, and central retinal vessels. It may be unilateral, typically with otherwise normal brain development, or bilateral with accompanying severe and widespread congenital malformations of the central nervous system.

A rare disorder characterized by the partial separation of the cerebral hemispheres. It is associated with mutations in the SIX3 gene.

Pierson syndrome (PIERS) is an autosomal recessive disorder comprising congenital nephrotic syndrome with diffuse mesangial sclerosis and distinct ocular abnormalities, including microcoria and hypoplasia of the ciliary and pupillary muscles, as well as other anomalies. Many patients die early, and those who survive tend to show neurodevelopmental delay and visual loss (summary by Zenker et al., 2004). Mutations in the LAMB2 gene also cause nephrotic syndrome type 5 with or without mild ocular anomalies (NPHS5; 614199).

Oculofaciocardiodental (OFCD) syndrome is a condition that affects the development of the eyes (oculo-), facial features (facio-), heart (cardio-), and teeth (dental). \n\nThe eye abnormalities associated with OFCD syndrome can affect one or both eyes. Many people with this condition are born with eyeballs that are abnormally small (microphthalmia). Other eye problems can include clouding of the lens (cataract) and a high risk of glaucoma, an eye disease that increases the pressure in the eye. These abnormalities can lead to vision loss or blindness.\n\nPeople with OFCD syndrome often have a long, narrow face with distinctive facial features, including deep-set eyes, droopy eyelids (ptosis), and a nose with a high bridge and broad tip. Affected individuals may have a split (cleft) in their nose or in the roof of their mouth (cleft palate).\n\nHeart defects are another common feature of OFCD syndrome. Babies with this condition may be born with a hole between two chambers of the heart (an atrial or ventricular septal defect) or a leak in one of the valves that controls blood flow through the heart (mitral valve prolapse).\n\nTeeth with very large roots (radiculomegaly) are characteristic of OFCD syndrome. Additional dental abnormalities can include the delayed loss of primary (baby) teeth, missing or abnormally small teeth, delayed teething (dentition), misaligned teeth, and defective tooth enamel.\n\nIndividuals with OFCD syndrome can have additional features, such as skeletal abnormalities (typically affecting the toes), hearing loss, and intellectual disabilities. 

Oculopalatocerebral syndrome is a rare disorder characterized by low birth weight, microcephaly, persistent hyperplastic primary vitreous, microphthalmia, large ears, small hands and feet, cleft palate, joint hypermobility, developmental delay, and cerebral atrophy (summary by Pellegrino et al., 2001).

Stickler syndrome is a connective tissue disorder that can include ocular findings of myopia, cataract, and retinal detachment; hearing loss that is both conductive and sensorineural; midfacial underdevelopment and cleft palate (either alone or as part of the Robin sequence); and mild spondyloepiphyseal dysplasia and/or precocious arthritis. Variable phenotypic expression of Stickler syndrome occurs both within and among families; interfamilial variability is in part explained by locus and allelic heterogeneity.

Verloes et al. (1992) described a rare variant of frontonasal dysplasia (see FND1, 136760), designated acromelic frontonasal dysplasia (AFND), in which similar craniofacial anomalies are associated with variable central nervous system malformations and limb defects including tibial hypoplasia/aplasia, talipes equinovarus, and preaxial polydactyly of the feet.

Persistent hyperplastic primary vitreous (PHPV), also termed 'persistent fetal vasculature,' is a developmental malformation of the eye in which the primary vitreous fails to regress in utero, resulting in the presence of a retrolental fibrovascular membrane with persistence of the posterior portion of the tunica vasculosa lentis and hyaloid artery. This abnormality is usually unilateral and associated with microphthalmia, cataract, glaucoma, and congenital retinal nonattachment (see Haddad et al., 1978; Khaliq et al., 2001; Prasov et al., 2012). PHPV shares phenotypic overlap with Norrie disease (310600). Genetic Heterogeneity of Persistent Hyperplastic Primary Vitreous A dominant form of PHPV has been described (PHPVAD; 611308).

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A), which includes both the more severe Walker-Warburg syndrome (WWS) and the slightly less severe muscle-eye-brain disease (MEB), is an autosomal recessive disorder with characteristic brain and eye malformations, profound mental retardation, congenital muscular dystrophy, and death usually in the first years of life. It represents the most severe end of a phenotypic spectrum of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (summary by Roscioli et al., 2012). For a general phenotypic description and a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type A, see MDDGA1 (236670).

Atelis syndrome-2 (ATELS2) is an autosomal recessive disorder characterized by poor overall growth with microcephaly and short stature, dysmorphic facial features, and congenital cardiac defects. Additional more variable features may include hematologic abnormalities, variable ocular abnormalities, motor delay, and anxiety. Patient cells exhibit a unique chromosomal instability phenotype consisting of segmented and dicentric chromosomes with mosaic variegated hyperploidy (Grange et al., 2022). See also ATELS1 (620184), caused by mutation in the SLF2 gene (610348). For a discussion of genetic heterogeneity of MVA, see MVA1 (257300).

Coloboma is an ocular birth defect resulting from abnormal development of the eye during embryogenesis. It is defined as a congenital defect in any ocular tissue, typically presenting as absent tissue or a gap, at a site consistent with aberrant closure of the optic fissure. Failure of fusion can lead to coloboma of one or multiple regions of the inferior portion of the eye affecting any part of the globe traversed by the fissure, from the iris to the optic nerve, including the ciliary body, retina, and choroid. Coloboma is also frequently associated with small (microphthalmic) or absent (anophthalmic) eyes as part of an interrelated spectrum of developmental eye anomalies, and can affect either one or both eyes (summary by Kelberman et al., 2014). Microphthalmia/coloboma-12 (MCOPCB12) is characterized by inter- and intrafamilial variability. In addition to microphthalmia and coloboma, other ocular anomalies include iris hypoplasia, aphakia or small lens, lens subluxation, congenital cataract, microcornea, and sclerocornea. Some patients also exhibit neurodevelopmental anomalies (Deml et al., 2016; Williamson et al., 2020). For a discussion of genetic heterogeneity of colobomatous microphthalmia, see MCOPCB1 (300345).

Neuroocular syndrome-1 (NOC1) encompasses a broad spectrum of overlapping anomalies, with developmental delay or impaired intellectual development as a consistent finding. Eye abnormalities show marked variability in the type and severity of defects, and include anophthalmia, microphthalmia, and coloboma. Other common systemic features include congenital heart and kidney defects, hypotonia, failure to thrive, and microcephaly (summary by Chowdhury et al., 2021). Genetic Heterogeneity of Neuroocular Syndrome See also NOC2 (168885), caused by mutation in the DAGLA gene (614015) on chromosome 11q12.