Figure 11-5 In CHRPE, the RPE cells are larger than normal and contain more densely packed melanin granules (arrows). For clinical images of CHRPE, see Chapter 17, Figure 17-10. (Courtesy of Hans E. Grossniklaus, MD.)
Inflammations
Infectious
Viral
Multiple viruses may cause retinal infections, including rubella, measles, human immunodeficiency virus (HIV), herpes simplex virus (HSV), varicella-zoster virus (VZV, or herpes zoster), and cytomegalovirus (CMV). Two of the most frequent clinical presentations of retinal viral infection, acute retinal necrosis (ARN) and CMV retinitis, are discussed here.
Acute retinal necrosis is a rapidly progressive, necrotizing retinitis caused by infection with HSV types 1 and 2, VZV, and, in rare instances, CMV. ARN can occur in healthy or immunocompromised persons. The histologic findings include inflammation in the vitreous and anterior chamber, with a prominent obliterative retinal vasculitis and retinal necrosis (Fig 11-6A). Electron microscopy has demonstrated viral inclusions in retinal cells (Fig 11-6B). Polymerase chain reaction (PCR) analysis of aqueous or vitreous biopsy specimens can be used to rapidly demonstrate the viral cause of ARN, reducing the need for other diagnostic techniques such as viral culture, intraocular antibody analysis, or immunohistochemistry.
CMV retinitis is an opportunistic infection that may occur in immunosuppressed patients, especially AIDS patients (Fig 11-7). This infection is histologically characterized by retinal necrosis, which leads to a thin fibroglial scar with healing. Acute lesions show large neurons (20–30 µm) that contain large eosinophilic intranuclear or intracytoplasmic inclusion bodies. At the cellular level, CMV may infect vascular endothelial cells, retinal neurons, and macrophages.
Figure 11-6 A, Acute retinal necrosis (ARN) is characterized by full-thickness necrosis of the retina (between arrows). B, Electron microscopy demonstrates viral particles (arrows) within retinal cells. (Courtesy of Hans E. Grossniklaus, MD.)
Figure 11-7 A, CMV retinitis/papillitis. Intraretinal hemorrhages and areas of opaque retina are present nasal to the optic disc. Note the marked optic disc and peripapillary retinal swelling and cotton-wool spots temporal to the optic disc. B,
Histologically, full-thickness retinal necrosis, cytomegalo cells, and intranuclear (arrowheads) and/or intracytoplasmic
inclusions are present. (Part A courtesy of R. Doug Davis, MD; part B courtesy of Robert H. Rosa, Jr, MD.)
Bacterial
See the discussion of endophthalmitis in Chapter 10 and in BCSC Section 9, Intraocular Inflammation and Uveitis.
Fungal
Fungal infections of the retina are uncommon, occurring almost exclusively in immunosuppressed patients as a result of fungemia. These infections usually begin as single or multiple foci of choroidal and retinal infection (Fig 11-8). The most common causative fungi are Candida species. Less common agents include Aspergillus species and Cryptococcus neoformans.
Histologically, fungal infections are typified by necrotizing granulomatous inflammation. A central zone of necrosis is typically surrounded by granulomatous inflammation, and a surrounding infiltrate of lymphocytes is common. With treatment, the lesions heal with a fibrous scar. The causative agent can usually be identified by culture or by the specific features of the fungal hyphae in histopathologic material.
Figure 11-8 A, Vitreous, retinal, and choroidal infiltrate in a patient with fungal chorioretinitis. B, Granulomatous infiltration surrounding central area of necrosis (asterisk). C, Gomori methenamine–silver nitrate stain of section parallel to B shows numerous fungal hyphae (black staining). (Courtesy of David J. Wilson, MD.)
Toxoplasmosis
Ocular toxoplasmosis, the most common infectious retinitis, may occur because of reactivation of congenitally acquired disease or as the result of an acquired Toxoplasma infection in healthy or