Bests Vitelliform Dystrophy

Epidemiology: The disorder is rare, with an incidence similar to Stargardt's disease.

Inheritance: The disorder is inherited as an autosomal dominant trait with variable penetrance and expressivity. The gene locus is on chromosome 11

Symptoms: Clinical manifestation occurs between the ages of 5 and 15 years. Initially there is a subjectively slight decrease in visual acuity. In the later stages of the disorder, vision is reduced to about 20/200.

Findings and diagnostic considerations: A typical feature of this form of macular dystrophy is that visual acuity is negligibly diminished at the onset of the disorder. However, the morphologic findings are remarkable. Ophthalmos-copy will reveal yellowish round vitelliform lesions in the macular region (Fig. 12.30) that look like the yolk of a fried egg. (The Latin word vitellus means egg yolk.) Usually these lesions are bilateral and symmetrical, although eccentric lesions may also occur. Table 12.7 lists the various manifestations.

Best's vitelliform dystrophy.

Best's vitelliform dystrophy.

Cholesterol Plaque Eye
Fig. 12.30 The yellow, sharply demarcated lesion appears like the yolk of a fried egg.

Table 12.7 Stages of Best's vitelliform dystrophy Stage Characteristics

Previtelliform stage Yellowish central pigment changes

Vitelliform stage Sharply demarcated yellow yolk-like lesion (see

Pseudohypopyon stage Settling of the yellow material

Vitelliruptive stage "Scrambling" of the yolk-like lesions with irregular yellow deposits

Scar stage Transition to scar

H The macular change resembling an egg yolk gave rise to the name vitelliform dystrophy.

Differential diagnosis: An unequivocal diagnosis can usually be made on the basis of the clinical picture alone. Sharply reduced or absent light response in the EOG and ERG confirms the presence of Best's vitelliform dystrophy.

Treatment: The causes of the disorder cannot be treated.

Prophylaxis: Examination of siblings and genetic counseling are indicated.

Clinical course and prognosis: The prognosis is more favorable than for Star-gardt's disease. The disorder is chronically progressive. Visual acuity in the better eye usually remains about 20/40. Secondary loss of visual acuity can result from subretinal neovascularization.

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