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Retinitis pigmentosa-90 (RP90) is characterized by early-onset night blindness, within the first decade of life. Patients exhibit other typical features of RP, including retinal vessel attenuation, optic disc pallor, and retinal pigment epithelium (RPE) atrophy and pigmentation abnormalities. Macular pseudocoloboma and cystoid macular edema have also been observed (Pierrache et al., 2017). For a discussion of genetic heterogeneity of RP, see 268000. [from OMIM]

Optic atrophy-9 (OPA9) is characterized by onset of decreased visual acuity and optic disc pallor in the first decade of life, with severely reduced visual acuity and color vision deficits observed in the third decade. Although initially described as an autosomal recessive disease (Metodiev et al., 2014; Kelman et al., 2018; Gibson et al., 2020), autosomal dominant cases of OPA9 have also been reported (Charif et al., 2021). Mutation in the ACO2 gene also causes a neurodegenerative disorder, infantile cerebellar-retinal degeneration (ICRD; 614559), of which optic atrophy is a feature. Dominant and Recessive OPA9 From a cohort of approximately 1,000 patients with optic atrophy, Charif et al. (2021) identified 50 probands with dominant mutations in the ACO2 gene, and 11 patients with biallelic variants. There was no significant difference in distribution of mutation type, with two-thirds of all variants being missense mutations in both groups, and nonsense, frameshift, and splice site mutations comprising the remaining third. Age at onset of symptoms occurred during the first 2 decades, without significant difference between dominant and recessive cases. Visual acuity was significantly more affected in recessive cases than in dominant ones, with more than 60% of eyes from the recessive group having a visual acuity lower than 20/200, whereas more than 80% of eyes from the dominant group had a visual acuity above 20/200. Analysis of the optic disc as well as retinal nerve fiber layer thickness measurements indicated a preferential involvement of the temporal quadrant in both patient groups. Assessment of color vision revealed highly variable alterations, including protan, deutan, and tritan types of dyschromatopsia. Some patients had additional retinal changes, including macular microcysts as well as macular dystrophy in 1 case. Extraocular symptoms were observed in 6 (12%) of the dominant cases and in 3 (27%) of the recessive cases, including hearing impairment in 2 dominant cases, and late-onset cerebellar ataxia in 1 dominant case and in 1 recessive case. [from OMIM]

Infantile cerebellar-retinal degeneration (ICRD) is a severe autosomal recessive neurodegenerative disorder characterized by onset between ages 2 and 6 months of truncal hypotonia, athetosis, seizures, and ophthalmologic abnormalities, particularly optic atrophy and retinal degeneration. Affected individuals show profound psychomotor retardation, with only some achieving rolling, sitting, or recognition of family. Brain MRI shows progressive cerebral and cerebellar degeneration (summary by Spiegel et al., 2012). A subset of patients may have a milder phenotype with variable features, including ataxia, developmental delay, and behavioral abnormalities (Blackburn et al., 2020). Mutation in the ACO2 gene also causes isolated optic atrophy (OPA9; 616289). [from OMIM]

2-hydroxyglutaric aciduria is a condition that causes progressive damage to the brain. The major types of this disorder are called D-2-hydroxyglutaric aciduria (D-2-HGA), L-2-hydroxyglutaric aciduria (L-2-HGA), and combined D,L-2-hydroxyglutaric aciduria (D,L-2-HGA).

The main features of D-2-HGA are delayed development, seizures, weak muscle tone (hypotonia), and abnormalities in the largest part of the brain (the cerebrum), which controls many important functions such as muscle movement, speech, vision, thinking, emotion, and memory. Researchers have described two subtypes of D-2-HGA, type I and type II. The two subtypes are distinguished by their genetic cause and pattern of inheritance, although they also have some differences in signs and symptoms. Type II tends to begin earlier and often causes more severe health problems than type I. Type II may also be associated with a weakened and enlarged heart (cardiomyopathy), a feature that is typically not found with type I.

L-2-HGA particularly affects a region of the brain called the cerebellum, which is involved in coordinating movements. As a result, many affected individuals have problems with balance and muscle coordination (ataxia). Additional features of L-2-HGA can include delayed development, seizures, speech difficulties, and an unusually large head (macrocephaly). Typically, signs and symptoms of this disorder begin during infancy or early childhood. The disorder worsens over time, usually leading to severe disability by early adulthood.

Combined D,L-2-HGA causes severe brain abnormalities that become apparent in early infancy. Affected infants have severe seizures, weak muscle tone (hypotonia), and breathing and feeding problems. They usually survive only into infancy or early childhood. [from MedlinePlus Genetics]

Gliomas are central nervous system neoplasms derived from glial cells and comprise astrocytomas, glioblastoma multiforme, oligodendrogliomas, ependymomas, and subependymomas. Glial cells can show various degrees of differentiation even within the same tumor (summary by Kyritsis et al., 2010). Ependymomas are rare glial tumors of the brain and spinal cord (Yokota et al., 2003). Subependymomas are unusual tumors believed to arise from the bipotential subependymal cell, which normally differentiates into either ependymal cells or astrocytes. They were characterized as a distinct entity by Scheinker (1945). They tend to be slow-growing, noninvasive, and located in the ventricular system, septum pellucidum, cerebral aqueduct, or proximal spinal cord (summary by Ryken et al., 1994). Gliomas are known to occur in association with several other well-defined hereditary tumor syndromes such as mismatch repair cancer syndrome (see 276300), melanoma-astrocytoma syndrome (155755), neurofibromatosis-1 (NF1; 162200) and neurofibromatosis-2 (see SWNV, 101000), and tuberous sclerosis (TSC1; 191100). Familial clustering of gliomas may occur in the absence of these tumor syndromes, however. Genetic Heterogeneity of Susceptibility to Glioma Other glioma susceptibilities include GLM2 (613028), caused by variation in the PTEN gene (601728) on chromosome 10q23; GLM3 (613029), caused by variation in the BRCA2 gene (600185) on chromosome 13q13; GLM4 (607248), mapped to chromosome 15q23-q26.3; GLM5 (613030), mapped to chromosome 9p21; GLM6 (613031), mapped to chromosome 20q13; GLM7 (613032), mapped to chromosome 8q24; GLM8 (613033), mapped to chromosome 5p15; and GLM9, caused by variation in the POT1 gene (606478) on chromosome 7q31. Somatic mutation, disruption, or copy number variation of the following genes or loci may also contribute to the formation of glioma: ERBB (EGFR; 131550), ERBB2 (164870), LGI1 (604619), GAS41 (602116), GLI (165220), DMBT1 (601969), IDH1 (147700), IDH2 (147650), BRAF (164757), PARK2 (602544), TP53 (191170), RB1 (614041), PIK3CA (171834), 10p15, 19q, and 17p13.3. [from OMIM]

Retinitis pigmentosa-46 (RP46) is characterized by night blindness, loss of peripheral vision, and reduced visual acuity. Funduscopic findings are typical of RP, including pale optic discs, attenuated retinal vessels, and intraretinal pigment deposits. Electroretinography shows substantial loss of rod and cone photoreceptor function (Hartong et al., 2008). For a discussion of genetic heterogeneity of retinitis pigmentosa, see 268000. [from OMIM]