Fuch's heterochromic cyclitis: new clues regarding pathogenesis.

UCHS HETEROCHROMIC CYCLITIS (FHC) IS A CHRONIC, typically unilateral anterior segment uveitis syndrome.1 It is usually painless with limited inflammation characterized by diffuse, scattered, small and mediumsized keratic precipitates with mild anterior chamber flare, minimal anterior chamber cells, and iris atrophy that leads to secondary, acquired heterochromia. Immunohistochemistry of iris biopsies reveals an inflammatory infiltrate consisting mainly of lymphocytes and plasma cells along with few mast cells and eosinophils.1 Unlike other uveitic syndromes, the disease does not respond to corticosteroid therapy. Thus, this disease challenges us both in its pathogenesis and in empiric strategies for treatment. Defining the pathogenesis in this and other uveitis syndromes will direct future approaches to both disease prevention and targeted therapy to limit disease morbidity and the long-term sequelae of ocular inflammation, such as cataract and glaucoma. Quentin and Reiber,2 in an article in this issue of THE JOURNAL, present new evidence that links the rubella virus with FHC, a provocative study that raises additional questions about the pathogenesis of FHC. Clues about immune pathogenesis in FHC come from analysis of the cellular infiltrate and proteins in the aqueous humor of affected individuals. The cellular infiltrate in the anterior chamber of patients with FHC mainly consists of T lymphocytes. Sampling of the aqueous humor during relative quiescence, at the time of cataract surgery, was performed in an earlier study by Murray and associates.3 Fifteen patients with FHC were sampled for that study, and analysis was performed by RNA extraction followed by reverse transcriptase polymerase chain reaction (RT-PCR). The investigators detected CD3, CD4, and CD8 mRNA, all markers of T lymphocytes, but did not detect CD19, a B-cell marker. The sensitivity of this method was not described, and the negative result for CD19 by RT-PCR does not exclude the presence of B