A Case of the Initial Presentation of Hemophagocytic Lymphohistiocytosis as Acute Unilateral Vision Loss.

Hemophagocytic lymphohistiocytosis (HLH) is an incredibly rare disease that is characterized by the overproduction of histiocytes and lymphocytes, which then start to attack the body instead of just invasive pathogens. It has been known to affect many organs including most commonly blood cells and bone marrow, but it has also been known to affect the liver, spleen, skin, and the brain. Ocular involvement is rare and is mostly associated with HLH's effect on other body systems (i.e., HLH causes extremely low platelets which can lead to retinal hemorrhages). However, we discuss a case report of a 19-year-old man whose initial presentation of HLH was complete vision loss in one eye. MRI showed inflammation of the nerve which initially appeared similar to optic neuritis. Only after the patient began having systemic symptoms, as well as further lab tests, bone marrow biopsy, and imaging, were we able to make the diagnosis of HLH. This is the first reported case in the literature of a patient with HLH's initial presenting symptom being acute unilateral vision loss. This finding is important for the ophthalmic community to be aware of, both because HLH needs to be included in the differential for rare causes of unilateral complete vision loss especially when associated with systemic atypical symptoms such as fever or altered mental status, and because early recognition of HLH by ophthalmologists could lead to life-saving treatment. If undiagnosed and untreated, HLH can be fatal in months.