The primary route of infection is through the lungs following an encounter with contaminated molds found in soil or from yeasts found in animals. During the initial infection, the patient may complain of fever, chills and malaise. H. Capsulatum or its by-products produce a lymphocytic infiltration within the choroid. This results in the formation of granulomatous inflammatory masses that disrupt Bruch's membrane and the retinal pigment epithelium and compromise the outer layers of the retina. In most cases, the resulting peripheral choroidopathies are mild, producing only subtly observable clinical signs that heal without complications within a few weeks.
Macular lesions possess serious ocular sequelae and progress through stages.
Their presentation can lag behind the systemic infection by 30 years. Stress or immunocompromise increases the risk of macular involvement and POHS reactivation. Stage 1 POHS maculopathy is marked by active choroiditis near the macula appearing as a yellow focus with fuzzy white borders. This stage may abort and resolve leaving only a small residual scotoma. Stage 5 is considered the end stage and is marked by maculopathy of more than two years and disciform scarring. .