Excerpt from Multifocal Choroidopathy Syndromes

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This group of rare disorders involves a primary pathologic process occurring at or near the level of the retinal pigment epithelium (RPE) with or without choriocapillaris involvement. Ultimately, the etiology is presumed to be either a vasculitic obstruction of the choriocapillaris with secondary infarction of the overlying RPE or, possibly, an immunologic response directed at the RPE itself. Many clinical features of these individual entities overlap, causing much confusion. Whether these conditions represent distinct entities or whether some may be parts of a spectrum of the same basic disease is still unknown.

Other conditions of choroiditis with overlying RPE involvement are not described in this article; yet, they are important to consider in the differential diagnosis of these more atypical choroiditides, such as tuberculosis, histoplasmosis, syphilis, posterior scleritis, reticulum cell sarcoma, lymphoid neoplasia, diffuse unilateral subacute neuroretinitis (DUSN), and Lyme disease, or the more common idiopathic syndromes, such as central serous retinochoroidopathy, sarcoidosis, Vogt-Koyanagi-Harada syndrome, and sympathetic ophthalmia.

Classification

Attempts at grouping these myriad disorders, especially by Gass, have resulted in inclusion of multiple evanescent white dot syndrome (MEWDS), acute idiopathic blind spot enlargement syndrome (AIBSES), acute macular neuroretinopathy (AMN), and multifocal choroiditis (MFC) or pseudo–presumed ocular histoplasmosis (pseudo-POHS) under the term acute zonal occult outer retinopathy (AZOOR) (Gass, 1993). This inclusion group arose primarily from the observation of a few case reports where 2 or 3 of these entities had coincident manifestation in the same patient (Jacobson et al, 1995).

AZOOR is characterized by the following common clinical features: minimal initial ophthalmoscopic changes, followed later by signs of retinochoroidal degeneration, rapid reduction in one or more parameters of the visual field, photopsia, and abnormalities on electrophysiologic testing (Francis et al, 2005).

More recently, AIBSES has been characterized to have sufficiently unique clinical features, such that, despite some similarities to MEWDS, treating it as a distinct and separate entity may be wise (Volpe et al, 2001; Machida et al, 2004; Watzke et al, 2002; Gass, 2001; Kondo et al, 2001). AMN, a bilateral condition affecting otherwise healthy young adults, appears to involve a pathologic process occurring more in the middle and outer retinal layers rather than in the RPE and choriocapillaris (Turbeville et al, 2003). As such, both AIBSES and AMN will not be discussed in this article.

There remains the conviction that the aforementioned entities are sufficiently distinct as to preclude any effective single inclusion group (Jampol et al, 1995). In the absence of any significant histopathologic and serologic findings, these conditions not only continue to present a problem as far as classification, but also remain poorly understood with regards to etiology or pathogenesis. The discussion of the various multifocal choroidopathy syndromes in this article will consider each entity separately and, in so doing, will avoid the thorny issue of endorsing any one classification.

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