PROZONE PHENOMENON IN AN ACUTE SYPHILITIC POSTERIOR PLACOID CHORIORETINOPATHY (ASPPC)

Abstract

Background: Prozone phenomenon occurs when a high concentration of antibodies in the blood interferes with formation of antibody-antigen complex which gives false negative serology results. Here we report prozone phenomenon in a case of Acute Syphilitic Posterior Placoid Chorioretinopathy (ASPPC) with co-infection of Human Immunodeficiency Virus (HIV).

Case report: A-30-year-old gentleman with HIV infection, recently started on highly active antiretroviral therapy (HAART) presented with four days history of blurring of vision.Visual acuity in the right eye was 6/12 and counting finger on left eye. Relative afferent pupillary defect was absent with unremarkable anterior segment. Fundus examination showed hypopigmented lesions corresponding to area of hyperfluorescence resembling patchy leopard spots and perivascular sheathing in fundus fluorescein angiography (FFA). Systemic examination was unremarkable except for lymphadenopathy. VDRL test reported non reactive. The suspicion of ASPPC was high based on clinical findings, thus VDRL test was repeated with higher dilution. The repeated VDRL was reactive and the patient was treated with intravenous ceftriaxone. Patient’s bilateral eye visual acuity improved to 6/9 and chorioretinitis resolved.

Conclusion: Prozone phenomenon needs to be considered in cases which are highly suggestive of syphilis infection despite a non-reactive VDRL.

Keywords: Prozone phenomenon, neurosyphilis, ASPPC, Human Immunodeficiency Virus