A histopathological, ultrastructural and immunohistochemical study of congenital hereditary retinoschisis.

OBJECTIVE: To confirm our earlier histopathological and electron microscopic findings in congenital hereditary retinoschisis (CHRS) in two additional globes and to further evaluate the nature and origin of the intraretinal filaments by means of immunohistochemical analysis. PATIENTS: 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 histopathological study and electron microscopy (patient I) and immunohistochemical analysis (all five globes).
RESULTS: Histopathological examination showed extensive extracellular deposition of amorphous material positive for 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 Müller cells, with accumulation of these filaments in adjacent extracellular spaces. Similar, less severe changes were seen in the superonasal retina. Immunohistochemical studies showed focal reactivity for glial fibrillary acidic protein (GFAP) in the retina adjacent to the schisis cavity in all five globes, focal reactivity for S-100 protein in four retinas, rare focal staining for vimentin and neurofilaments in two retinas each and no reactivity for type I keratin or actin.
CONCLUSIONS: The present study corroborates our previous work and provides pathological evidence that the retinal disorder extends beyond the limits of the schisis. The results of the immunohistochemical analysis are consistent with a glial cell origin of the filaments. We postulate that defective Müller cells produce GFAP and possibly S-100 protein, which accumulate within the retina and secondarily result in degeneration of these cells and schisis formation.