A HISTOPATHOLOGICAL, ULTRASTRUCTURAL AND IMMUNOHISTOCHEMICAL STUDY OFCONGENITAL HEREDITARY RETINOSCHISIS

Objective: To confirm our earlier histopathological and electron micro scopic findings in congenital hereditary retinoschisis (CHRS) in two a dditional globes and to further evaluate the nature and origin of the intraretinal filaments by means of immunohistochemical analysis. Patie nts: Three white men with CHRS, aged 83 years (patient I) (two globes) , 55 years (patient 2) (two globes) and 33 years (patient 3, nephew of patient 2) (one globe), Outcome measures: Findings on histopathologic al study and electron microscopy (patient I) and immunohistochemical a nalysis (all five globes). Results: Histopathological examination show ed extensive extracellular deposition of amorphous material positive f or periodic acid-Schiff reagent in the outer schisis layer and focally in the macula, Ultrastructurally, the amorphous material represented filaments measuring 8 to 12 nm in diameter within degenerated Muller c ells, with accumulation of these filaments in adjacent extracellular s paces. Similar, less severe changes were seen in the superonasal retin a. Immunohistochemical studies showed focal reactivity for glial fibri llary acidic protein (GFAP) in the retina adjacent to the schisis cavi ty in all five globes, focal reactivity for S-100 protein in four reti nas, rare focal staining for vimentin and neurofilaments in two retina s each and no reactivity for type I keratin or actin. Conclusions: The present study corroborates our previous work and provides pathologica l evidence that the retinal disorder extends beyond the limits of the schisis. The results of the immunohistochemical analysis are consisten t with a glial cell origin of the filaments. We postulate that defecti ve Muller cells produce GFAP and possibly S-100 protein, which accumul ate within the retina and secondarily result in degeneration of these cells and schisis formation.