Adult vitelliform macular dystrophy (AVMD) is generally regarded as a separate entity from juvenile-onset vitelliform macular dystrophy or Best Disease. AVMD has also been known by several other names, including adult-onset foveomacular vitelliform dystrophy (AOFVD), adult vitelliform dystrophy, and pattern dystrophy. Pattern dystrophies are a collection of macular diseases characterized by various patterns of pigment deposition within the retinal pigment epithelium (RPE) of which AVMD is a subset. Compared to Best disease, AVMD typically begins later in life (typically between 40 and 60 years of age), and the lesions are smaller (about 1/2 to 1/3 disc diameters in size; ▶ Fig. 33.1). AVMD is typically associated with somatic mutations of the gene PRPH2 on chromosome 6, although there are cases of families where multiple members have AVMD. PRPH2 is responsible for producing a protein called peripherin 2, a stabilizing glycoprotein found in the outer segments of rods and cones. Loss of peripherin 2 leads to photoreceptor cell loss and accumulation of lipofuscin within the RPE. If older patients are found to have defects in BEST1 and not PRPH2 then they are suffering from Best disease and not AVMD. The lesions in Best disease can also display layering of the yellow subretinal pigment in dependent areas of the lesion which is typically not seen in AVMD. This would eliminate any confusion regarding the distinction between AVMD and a milder form of Best disease.
Fig. 33.1 (a) Color photo of the left eye with a round, yellow, subfoveal lesion with a central pigment clump. (b) Fundus autofluorescence with a central hypo-autofluorescent lesion surrounded by an irregular hyper-autofluorescent ring centered at the fovea. (c) Optical coherence tomography of the left eye with an ovoid, subretinal, hyperreflective lesion centered at the fovea with a small amount of overlying subretinal fluid and overlying loss of the ellipsoid zone. Early stage fluorescein angiogram at 44 seconds which shows blocking centrally over the fovea consistent with the yellow subretinal lesion on color photos. (d) There is a surrounding irregular hyperfluorescent ring that does not increase in size or leak on a (e) later fluorescein angiogram at 8 minutes. f,g Fundus photo with bilateral, symmetric, about 1/3 disc diameter in size, yellow, subretinal lesions with a central pigment clump. Note the parafoveal yellow, drusen-like deposits in both eyes.