Presumed ocular histoplasmosis syndrome: A case of masked identity

Presumed ocular histoplasmosis syndrome (POHS) is a clinical condition characterized by multiple chorioretinal scars (histo spots), peripapillary atrophy (PPA), and development of choroidal neovascularization (CNV).[1] Typically, anterior segment and vitreous inflammation are absent. Histoplasma capsulatum, a dimorphic fungus, is considered to be the causative agent of POHS, but its exact etiology is unclear till now. It is thought to be caused by hematogenous dissemination of the fungus to choroidal circulation, explained by the Choroidal Seeding Theory.[2] Here, we report the clinical features of a rare POHS with CNV. Case Report A 30-year-old female presented in the outpatient department with a complaint of left eye diminution of vision for 2 years. She had a history of blunt trauma in the right eye 15 years back, and cataract surgery with intraocular lens implantation in the left eye 5 years back. There was no light perception in the right eye, whereas best-corrected visual acuity of the left eye was finger counting close to the face. The refractive error in the left eye was −2.00 DC *70. Anterior segment examination revealed phthisis bulbi in the right eye whereas the left eye was pseudophakic. Fundus examination of the left eye showed clear media with circumferential PPA, and multiple whitish yellow punched-out lesions associated with predominantly scarred choroidal neovascular membrane (CNVM) at fovea [Figure 1a and b]. Optical coherence tomography (OCT) and fundus autofluorescence (FAF) of the left eye confirmed the presence of CNV [Figures 2 and 3]. Other common causes of chorioretinal scars and CNV such as ocular tuberculosis, toxoplasmosis, and HIV were ruled out based on clinical history and clinical picture. A diagnosis of left eye POHS was considered based on the clinical findings and imaging.Figure 1: (a) Fundus photo showing multiple chorioretinal scars (histo sposts) from posterior pole to periphery, (b) Posterior pole showing circumferential peripapillary atrophy and choroidal neovascularization at maculaFigure 2: Fundus autofluorescence image showing small round hypoautofluorescent areas corresponding to nonpigmented chorioretinal scarsFigure 3: Predominantly scarred Choroidal neovascularization with some activity can be seen in optical coherence tomography image (arrow). Outer retinal atrophy (arrowhead) with surrounding normal retinal layer corresponding to histo spots (punched out lesions)Discussion A direct cause–effect relationship between histoplasma infection and the clinical syndrome has been indefinite; hence, the term Presumed is added to ocular histoplasmosis syndrome. Majority of cases are subclinical and asymptomatic until they are complicated by the development of CNV which results in visual impairment. Chorioretinal scars which are also known as histo spots are typically round/oval punched-out lesions with diffuse borders, random distribution, and variable pigmentation. The prognosis of POHS is overall good until it gets complicated with CNV. Various imaging modalities such as fluorescein angiography, OCT angiography, and FAF can assist in the diagnosis of POHS.[1,3] Differential diagnosis of POHS includes the spectrum of conditions known as white dot syndrome, and other causes of CNV such as idiopathic CNV, myopic CNV, and exudative age related macular degeneration (AMD). Furthermore, infectious diseases such as ocular toxoplasmosis, sarcoidosis, and serpiginous choroiditis/serpiginous like choroiditis must be ruled out before making a diagnosis of POHS.[1] Although these conditions mimic the lesions similar to POHS they are present with anterior segment findings, unlike POHS. Thus POHS is exclusively diagnosed based on retinal features involving multiple histo spots, PPA, and CNV. Histoplasmic skin test has been suggested previously; however, it is not routinely performed due to complications associated with it. In the present scenario, we did not perform any skin test and made a diagnosis based on clinical findings.[2] A study by reported negative results if skin tests in confirmed cases of POHS.[4] No primary prevention of POHS is possible. Asymptomatic patients can be observed and monitored by Amsler grid screening for CNV development. Treatment of POHS is focused on CNV, with the use of intravitreal injections of anti-vascular endothelial growth factor. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.