Epidemiology and Clinical Features

The prevalence of SC is rare, and reported cases in literature ranges from 0% to 5.4% of posterior uveitis with the highest reported cases in India. (Biswas et al. 1996; McCannel et al. 1996; Nazari Khanamiri and Rao 2013) SC has been traditionally reported as a disease of otherwise healthy Caucasians; the high reported percentage of cases in India may represent the tuberculosis variant of multifocal serpiginous choroiditis. Patients with SC are usually otherwise healthy, middle-aged, in fifth to sixth decade, although the age range can vary widely from 11 to 70 years (Abrez et al. 2007; Nazari Khanamiri and Rao 2013). There is a slight gender predilection for males (Abrez et al. 2007).

Serpiginous choroiditis is typically bilateral, but patients may present asymmetrically. Patients may complain of blurred vision or small central or paracentral scotoma. They may be asymptomatic before foveal involvement. The average time between presentation in one eye and onset in the other eye may be up to 5 years (Chisholm et al. 1976).

On clinical exam, serpiginous choroiditis is predominantly a posterior uveitis with minimal to no anterior chamber inflammation; vitritis may be present in about 30% of the cases, and it is mild (Mirza and Jampol 2006). The creamy-white lesions emanate in pseudopodial fashion from the optic nerve. Disease activity is confined to the leading edge of the lesion and may be associated with shallow subretinal fluid and/or vascular sheathing. It shows choriocapillaris and RPE atrophy and subretinal fibrosis (Fig. 2.2). RPE hyperpigmentation is present at the periphery of the lesions. New lesions occur on the border of old scars (Fig. 2.3). Vision may be severely affected if choroidal neovascularization in macula occurs, which can happen in up to 25% of cases (Christmas et al. 2002; Jampol et al. 1979; Laatikainen and Erkkila 1981). Final visual outcome can range from 20/200 to count fingers.

In about one third of patients, patients may present with creamy yellow lesions solely in the macula, termed macular serpiginous choroiditis (Fig. 2.4) (Hardy and Schatz 1987; Mansour et al. 1988). Choroidal neovascularization develops more frequently and earlier in the course of the disease, thereby carries a poorer prognosis.

Pathogenesis

The etiology of serpiginous choroiditis is unknown; possible etiologies may be autoimmune, infectious, vascular, or degenerative (Mirza and Jampol 2006). There is no consistent HLA association with SC, although there appears to be a higher frequency of HLA-B7, HLA-A2, HLA-B8, and HLA-Dw3 (Laatikainen and Erkkila 1981). Broekhuyse and colleagues also found an immune response to retinal S antigen but not to opsin, in SC (Broekhuyse et al. 1988). Given that clinical and imaging studies localize the inflammatory disease of SC to choroid and RPE, the sensitivity to retinal S antigen may be a secondary effect due to extensive damage of retina by serpiginous choroiditis. In histopathology of serpiginous lesion, there is extensive loss of RPE with loss of overlying retina and monocular cell infiltrate in choriocapillaris (Wu et al. 1989). SC responds remarkably well to anti-inflammatory effects of steroids and immune-suppressive therapy. It has been hypothesized that SC is an autoimmune and organ-specific disease of the eye (Nazari Khanamiri and Rao 2013).

Imaging and Ancillary Diagnostic Tools

Fluorescein and indocyanine green angiography support the diagnosis and management of SC. Progression can be followed with fundus autofluorescence imaging. Choroidal neovascularization, RPE changes, and atrophy can be followed with optical coherence tomography (OCT). Newer studies like microperimetry and optical coherence tomography angiography (OCT-A) are gaining importance in the management of the disease.

Fluorescein Angiography

Fluorescein angiography shows classic blockage of choroidal flush in early phase, early hypofluorescence (Fig. 2.5), and late hyperfluorescence of active lesion. Early hypofluorescence may be secondary to inflammatory occlusion of choriocapillaris or blocked fluorescence by retinal pigment epithelium edema (Quillen and Blodi 2002; Mirza and Jampol 2006). Active SC appears as hypofluorescent patches with poorly, ill-defined hyperfluorescence of outer borders of serpiginous lesions (Fig. 2.6). The fluorescein angiogram is characteristic and has been described as “fingers” of affected tissue because the hyperfluorescence occurs at the edge of the lesion and spreads inward (Mirza and Jampol 2006). In late phases of FA, active lesions appear as uniform or spotty hyperfluorescence from leaking large choroidal vessels (Nazari Khanamiri and Rao 2013). Atrophic lesions show diffuse loss of pigment, choroidal vessels, late staining on fluorescein angiography (Fig. 2.7).