Original descriptions of the disease emphasized posterior pole involvement, with initial multifocal lesions throughout the posterior pole that progressed later to confluence, and involved the peripheral retina at late stages. This is likely a reflection of the severely immunocompromised state of affected patients. If present, it was found to be predominantly mild. Less than approximately 40% of patients have an anterior chamber reaction and less than 20% have vitreous cell.
An acute reactive inflammatory granulomatous response within the retinal and choroidal vasculature also plays a role in retinal ischemia, however this occlusive vasculitis is a more prominent feature of ARN than PORN.Ī hallmark feature of PORN is the lack of intraocular inflammation. Histology is significant for necrosis not only of the outer retina but all retinal layers. Retinal necrosis is inflicted predominantly through direct intraretinal spread of the replicating virus. In a study, 73% patients had a history of cutaneous zoster and 73% patients had suspected viral involvement of the central nervous system.
#Normal retina vs cmv retinitis skin
Of patients with history of cutaneous involvement, 41% involved the V1 distribution and 14% had concurrence of skin and intraocular manifestations. Approximately 22% of patients cited a history of cutaneous zoster. The median age was cited as 37 years (range 6 - 58 ). In patients with AIDS, the mean CD4 count at the time of PORN diagnosis was found to be 21, ranging from 1-130 (normal 500-1500). PORN occurs in patients who are severely immunocompromised. Additionally, some studies have only identified CMV in vitreous that is co-infected with HSV-1. The role of CMV as an etiologic agent in PORN remains controversial, however, as often evidence of CMV-retinitis is an exclusion criteria in a number of studies. Second were HSV strains, and in rare cases CMV has been cited as well. al) identified VZV as the etiologic agent in 71.5% of cases of PORN. The overwhelming majority of cases of PORN are attributed to infection by Varicella Zoster Virus (VZV). Significantly less ocular inflammatory reaction is noted in PORN compared to ARN. PORN has also been called as rapidly progressive herpetic retinal necrosis (RPHRN). Since then, our understanding of the disease has evolved, but these remain the salient features. They described an infectious retinitis associated with recent cutaneous zoster infection, marked by limited intraocular inflammation, predominant involvement of the outer retina, and involvement of the posterior pole. In 1990, Forster and colleagues identified a syndrome affecting immunocompromised individuals and coined the term "progressive outer retinal necrosis," or PORN. This disease process was generally found to occur in otherwise healthy patients. In 1971, Akira Urayama described acute retinal necrosis (ARN) as consisting of a clinical syndrome of an acute unilateral panuveitis associated with retinal periarteritis and necrotizing retinitis.
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