MedGen

Mevalonic aciduria (MEVA), the first recognized defect in the biosynthesis of cholesterol and isoprenoids, is a consequence of a deficiency of mevalonate kinase (ATP:mevalonate 5-phosphotransferase; EC 2.7.1.36). Mevalonic acid accumulates because of failure of conversion to 5-phosphomevalonic acid, which is catalyzed by mevalonate kinase. Mevalonic acid is synthesized from 3-hydroxy-3-methylglutaryl-CoA, a reaction catalyzed by HMG-CoA reductase (142910). Mevalonic aciduria is characterized by dysmorphology, psychomotor retardation, progressive cerebellar ataxia, and recurrent febrile crises, usually manifesting in early infancy, accompanied by hepatosplenomegaly, lymphadenopathy, arthralgia, and skin rash. The febrile crises are similar to those observed in hyperimmunoglobulinemia D and to periodic fever syndrome (HIDS; 260920), which is also caused by mutation in the MVK gene (summary by Prietsch et al., 2003). [from OMIM]

Any retinitis pigmentosa in which the cause of the disease is a mutation in the NR2E3 gene. [from MONDO]

Cataract is an opacification of the lens or lens capsule in the eye and is the most common cause of childhood blindness in the world, with an incidence of 1 to 3 per 10,000 live births. If untreated in infancy or childhood, it frequently causes visual impairment and can result in irreversible amblyopia. Nuclear cataract refers to opacification within the embryonal and/or fetal nuclei of the lens (summary by Berry et al., 2013). [from OMIM]

Hyperferritinemia-cataract syndrome is a disorder characterized by an excess of an iron storage protein called ferritin in the blood (hyperferritinemia) and tissues of the body. A buildup of this protein begins early in life, leading to clouding of the lenses of the eyes (cataracts). In affected individuals, cataracts usually develop in infancy, rather than after age 60 as typically occurs in the general population. Cataracts that are not removed surgically cause progressive dimming and blurriness of vision because the clouded lenses reduce and distort incoming light.

Although the hyperferritinemia in this disorder does not usually cause any health problems other than cataracts, the elevated ferritin levels in the blood can be mistaken for a sign of certain liver disorders. These conditions result in excess iron in the body and may be treated by blood-drawing. However, individuals with hyperferritinemia-cataract syndrome do not have an excess of iron, and with repeated blood draws will develop reduced iron levels leading to a low number of red blood cells (anemia). Therefore, correct diagnosis of hyperferritinemia-cataract syndrome is important to avoid unnecessary treatments or invasive test procedures such as liver biopsies. [from MedlinePlus Genetics]

Retinitis pigmentosa-56 (RP56) is an early-onset form of RP with progressive visual-field loss and deterioration of visual acuity (Bandah-Rozenfeld et al., 2010). For a general phenotypic description and a discussion of genetic heterogeneity of retinitis pigmentosa, see 268000. [from OMIM]

Any early-onset non-syndromic cataract in which the cause of the disease is a mutation in the NHS gene. [from MONDO]

Stomatin-deficient cryohydrocytosis with neurologic defects is an autosomal dominant disorder characterized by delayed psychomotor development, seizures, cataracts, and pseudohyperkalemia resulting from defects in the red blood cell membrane. The disorder combines the neurologic features of Glut1 deficiency syndrome-1 (GLUT1DS1; 606777), resulting from impaired glucose transport at the blood-brain barrier, and hemolytic anemia/pseudohyperkalemia with stomatocytosis, resulting from a cation leak in erythrocytes (summary by Bawazir et al., 2012). For a discussion of clinical and genetic heterogeneity of red cell stomatocyte disorders, see 194380. [from OMIM]

Mutations in the GJA8 gene have been found to cause several types of autosomal dominant cataract, which have been described as congenital, zonular pulverulent, nuclear progressive, nuclear pulverulent, stellate nuclear, nuclear total, total, and posterior subcapsular. Cataract associated with microcornea, sometimes called the cataract-microcornea syndrome, is also caused by mutation in the GJA8 gene. Before it was known that mutation in the GJB8 gene caused multiple types of cataract, this entry was titled 'Cataract, zonular pulverulent, 1,' with the symbols CZP1, CZP, and CAE1. [from OMIM]

Congenital cataracts cause 10 to 30% of all blindness in children, with one-third of cases estimated to have a genetic cause (summary by Bu et al., 2002). Mutations in the HSF4 gene have been found to cause multiple types of cataract, which have been described as infantile, lamellar, zonular, nuclear, anterior polar, stellate, and Marner-type. The preferred title for this entry was formerly 'Lamellar Cataract,' with 'Cataract, Marner Type; CAM; CTM' an included title. [from OMIM]

Mutation in the CRYBA4 gene has been found in families with cataract described as congenital, lamellar, and nuclear. [from OMIM]

Familial exudative vitreoretinopathy is a hereditary disorder that can cause vision loss that worsens over time. This condition affects the retina, the specialized light-sensitive tissue that lines the back of the eye. In people with this disorder, blood vessels do not fully develop at the outer edges (periphery) of the retina, which reduces the blood supply to this tissue. This prolonged reduction in blood supply (chronic ischemia) causes continued damage to the retina and can lead to worsening of the condition. 

The signs and symptoms of familial exudative vitreoretinopathy vary widely, even within the same family. In many affected individuals, the retinal abnormalities never cause any vision problems. Other people with this condition develop abnormal vessels that leak. This  causes chronic inflammation which, over time, can lead to fluid under the retina (exudate). A reduction in the retina's blood supply causes the retina to fold, tear, or separate from the back of the eye (retinal detachment). The resulting retinal damage can lead to vision loss and blindness. Other eye abnormalities are also possible, including eyes that do not look in the same direction (strabismus) and a visible whiteness (leukocoria) in the normally black pupil.

Some people with familial exudative vitreoretinopathy also have a condition known as osteoporosis-pseudoglioma syndrome, which is characterized by reduced bone density. People with this condition have weakened bones and an increased risk of fractures. [from MedlinePlus Genetics]

Mutations in the FYCO1 gene have been identified in families with autosomal recessive cataract described as congenital and congenital nuclear. The preferred title/symbol of this entry was formerly 'Cataract, Autosomal Recessive Congenital 2; CATC2.' [from OMIM]

Mutations in the CRYBB1 gene have been found to cause multiple types of cataract, which have been described as congenital nuclear, congenital nuclear with anterior and posterior Y-suture and polar opacities, and pulverulent. The preferred title/symbol for this entry was formerly 'Cataract, Congenital Nuclear, Autosomal Recessive 3; CATCN3.' [from OMIM]

Mutations in the CRYBA1 gene have been found to cause multiple types of cataract, which have been described as congenital zonular with sutural opacities, congenital nuclear progressive, and progressive lamellar. The preferred title/symbol of this entry was formerly 'Cataract, Congenital Zonular, with Sutural Opacities; CCZS.' [from OMIM]

Mutations in the BFSP1 gene have been found to cause multiple types of cataract, which have been described as cortical, nuclear, and progressive punctate lamellar. Both autosomal dominant and autosomal recessive modes of inheritance have been reported. [from OMIM]

Mutations in the MIP gene have been found to cause multiple types of cataract, which have been described as 'polymorphic,' progressive punctate lamellar, cortical, anterior and posterior polar, nonprogressive lamellar with sutural opacities, embryonic nuclear, and pulverulent cortical. [from OMIM]

Mutations in the CRYBB3 gene have been identified in families with cataract, described as congenital nuclear cataract with cortical riders, nuclear, posterior polar, anterior polar, and cortical. The preferred title/symbol of this entry was formerly 'Cataract, Congenital Nuclear, Autosomal Recessive 2; CATCN2.' [from OMIM]

Mutation in the CRYGS gene has been identified in multiple types of cataract, which have been described as progressive polymorphic anterior, posterior, peripheral cortical, sutural, and lamellar. [from OMIM]

Mutations in the CRYGC gene have been found to cause several types of cataract, which have been described as Coppock-like; embryonic, fetal, infantile nuclear; zonular pulverulent; and lamellar. Some patients also exhibit microcornea. Before it was known that mutations in the CRYGC gene cause several types of cataract, this entry was titled 'Cataract, Coppock-like,' with the symbol CCL. [from OMIM]

Mutations in the CHMP4B gene have been found to cause multiple types of cataract, which have been described as posterior polar, progressive posterior subcapsular, nuclear, and anterior subcapsular. The preferred title/symbol of this entry was formerly 'Cataract, Posterior Polar, 3; CTPP3.' [from OMIM]