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Fish-eye disease
Disease definition
Fish eye disease (FED) is a form of genetic LCAT (lecithin-cholesterol acyltransferase) deficiency (see this term) characterized clinically by corneal opacifications, and biochemically by significantly reduced HDL cholesterol and partial LCAT enzyme deficiency.
ORPHA:79292
Classification level: Subtype of disorderSummary
Epidemiology
Fish eye disease is very rare; about 30 cases have been reported to date. Fish eye disease seems to be less common than familial LCAT deficiency (see this term).
Clinical description
Corneal opacities are progressive and are observed from an early age (adolescence or young adulthood) and sometimes result in visual impairment. These lesions are generally more severe than in complete LCAT deficiency (familial LCAT deficiency, see this term) and form a mosaic pattern of small dot-like grey-white opacities. Signs of atherosclerosis have only been reported in rare cases although patients have low HDL cholesterol levels. Hepatomegaly, splenomegaly and lymphadenopathy are generally not present.
Etiology
18 different mutations in the LCAT gene (16q22.1), encoding the LCAT enzyme which catalyzes the formation of cholesterol esters in lipoproteins, have been identified in FED cases. In patients with this disorder, alpha-LCAT activity (i.e., the activity of LCAT in esterifying cholesterol within HDL) is abolished, but beta-LCAT activity (i.e., the activity of LCAT in esterifying cholesterol within other lipoproteins) is preserved. Impaired enzyme function is thought to result in deposition of lipids in the cornea.
Diagnostic methods
Initial diagnosis is suspected on the basis of corneal clouding. Definitive diagnosis requires molecular genetic testing of the LCAT gene and functional analysis of the gene product.
Differential diagnosis
Differential diagnosis includes Schnyder corneal dystrophy as well as familial LCAT deficiency and Tangier disease (see these terms).
Antenatal diagnosis
Prenatal diagnosis is possible.
Genetic counseling
FED follows an autosomal recessive pattern of inheritance. Genetic counseling should be offered to affected families.
Management and treatment
Treatment is symptomatic. Severe visual impairment may require corneal transplantation.
Prognosis
Morbidity is related to progressive corneal opacification, which may lead to visual impairment.
Additional information