Retinal Dystrophy, Reticular Pigmentary, Of Posterior Pole

Description

Reticular pigmentary retinal dystrophy is a form of patterned dystrophy (see MDPT1, 169150) characterized by a reticular pattern of pigmentation that likely appears in infancy and may be fully developed at age 15 years. Indirect funduscopy has shown that the condition is bilateral and symmetric and that the pigmentary deposits are localized below the neuroepithelium, very likely in the pigment epithelium. The reticulum extends from the macula in all directions, sparing the midperiphery and periphery. Visual acuity is unaffected or only minimally affected in advanced stages. Retinal function testing is normal, although the electrooculogram and dark adaptation can be at the lower limit of normal values (summary by Schauwvlieghe et al., 2013).

Clinical Features

This condition, first described by Sjogren (1950), is characterized by a peculiar network of black pigmented lines in the posterior pole of the retina, resembling a fishnet with knots. In late stages the network disappears and drusen appear. Deutman and Rumke (1969) described the disorder in a Dutch brother and sister whose parents were second cousins. The parents in the family reported by Sjogren (1950) were also related. Deafness and spherophakia in that family were probably independent recessive traits.

Schauwvlieghe et al. (2013) described 3 children with reticular dystrophy, 2 North American sisters, aged 10 years and 14 years, and an unrelated 12-year-old Belgian boy. In all 3 patients, both retinas showed the typical symmetric deep reticular pattern of pigmentation, forming a fishnet with knots. The peripapillary, parafoveal, and peripheral fundus were spared. Fluorescein angiography in the sisters revealed a wider area of involvement than was clinically apparent, and blocked the background fluorescence in a fishnet shape, indicating that the pigmented material that accumulated in the retinal pigment epithelium (RPE) blocks background fluorescence. Variation in the presence of autofluorescent chromophores was observed, with the older sister and the unrelated boy exhibiting a milder and more punctiform hyperautofluorescence of the net, whereas the younger sister showed a more intense hyperautofluorescent pattern. Spectral-domain optical coherence tomography showed material between the RPE and Bruch membrane, which the authors suggested was likely a mixture of pigment and lipofuscin. In addition, there was RPE thickening alternating with less-well delineated or even atrophic-appearing areas, with a normal-appearing choroid. Multifocal electroretinography did not show any changes in the hyperpigmented areas, suggesting that photoreceptors were well preserved and that the underlying choroid was intact.

Inheritance

Schauwvlieghe et al. (2013) noted that 2 sisters with reticular pattern dystrophy whose parents were unaffected suggests autosomal recessive inheritance. Autosomal dominant inheritance has been suggested by others (see 179840).

Molecular Genetics

Exclusion Studies

In a 12-year-old Belgian boy with reticular pattern dystrophy, Schauwvlieghe et al. (2013) excluded mutation in the ABCA4 (601691) and PRPH2 (179605) genes, as well as in the 3242A-G mutation in the MTTL1 gene (590050.0001).