Macular dystrophies are inherited retinal dystrophies in which various forms of deposits, pigmentary changes, and atrophic lesions are observed in the macula lutea, the cone-rich region of the central retina. Vitelliform macular dystrophies (VMDs) form a subset of macular dystrophies characterized by round yellow deposits, usually at the center of the macula and containing lipofuscin, a chemically heterogeneous pigment visualized by autofluorescence imaging of the fundus (summary by Manes et al., 2013). Vitelliform macular dystrophy-4 is characterized by late-onset moderate visual impairment, small satellite drusen-like lesions in the foveal area, preservation of retinal pigment epithelium (RPE) reflectivity, deposits above the RPE between the ellipsoid and outer segment interdigitation lines on spectral-domain optical coherence tomography (SD-OCT), and normal or borderline results on electrooculography (EOG) (Meunier et al., 2014). In most families with VMD4 caused by compound heterozygous or homozygous mutations in IMPG1, asymptomatic heterozygous carriers have been found to have fundus changes (Manes et al., 2013; Brandl et al., 2017).
Brandl et al. (2017) examined patients VMD4, caused by mutation in the IMPG1 gene, and VMD5 (616152), caused by mutation in the IMPG2 gene, and observed strikingly similar phenotypic characteristics. They noted that retinal lesions progressed in consecutive stages, with the initial development of a single vitelliform lesion in the central macula, with detachment of the neurosensory retina and hyperreflective material located above a preserved Bruch membrane/RPE on SD-OCT. Next, resorption of the hyperreflective material occurs, leaving behind a dome-shaped, optically empty cavity; alternatively, the foveal cavity formed by retinal detachment may become successively filled with material. Finally, there is collapse of the cavity with central retinal atrophy and loss of RPE, resulting in the most pronounced loss of visual acuity. The authors also noted that symptoms tended to be more severe in those with IMPG1 mutations.
For a discussion of genetic heterogeneity of vitelliform macular dystrophy, see VMD1 (153840). [from
OMIM]