A Rare and Deadly Complication of West Nile Virus: Unveiling the Mystery of Hemophagocytic Lymphohistiocytosis
A man in Switzerland battles a life-threatening condition, and the culprit is a virus with a global reach.
West Nile Virus (WNV), a single-stranded RNA virus, has been making headlines since its discovery in 1937, and for good reason. This mosquito-borne virus has spread its wings across the globe, sparing only Antarctica. But here's where it gets controversial—its impact on human health is a double-edged sword. While most infected individuals experience mild symptoms, a small percentage face a potentially fatal complication known as hemophagocytic lymphohistiocytosis (HLH).
HLH is a rare and often underdiagnosed condition characterized by an overstimulated immune response, leading to systemic inflammation, cytokine storm, and organ failure. It can be primary, linked to genetic factors in children, or secondary (reactive hemophagocytic syndrome, RHS), triggered by infections, malignancies, or autoimmune diseases. And this is the part most people miss—WNV can be a silent instigator of RHS, a fact that demands attention.
In a case study from Switzerland, a 62-year-old man with a history of prostate cancer presented with fever, diarrhea, and vomiting after returning from Toulon, France. His condition worsened, revealing septic shock, thrombocytopenia, lymphocytopenia, and acute kidney injury. Despite extensive testing, the cause remained elusive until an HLH diagnosis was considered.
The patient's fever persisted, and his kidney function deteriorated. Pancytopenia, hyperferritinemia, and elevated liver enzymes raised suspicions. An HScore of 244, indicating a high probability of HLH, prompted further investigation. Interestingly, bone marrow biopsy showed no evidence of hemophagocytosis, a classic HLH feature. But here's the twist—WNV sequences were detected in the patient's serum, suggesting a viral trigger.
As the patient's mental status declined, cerebrospinal fluid analysis hinted at meningoencephalitis. Ophthalmological evaluation revealed uveitis and chorioretinal lesions, pointing to WNV chorioretinitis. Serology and blood PCR confirmed the WNV infection, despite negative results from cerebrospinal fluid testing.
This case highlights an atypical manifestation of WNV infection, featuring meningoencephalitis, ophthalmological involvement, and secondary HLH. The diagnosis was challenging due to the absence of hemophagocytosis in the bone marrow biopsy, but the pathognomonic chorioretinal findings provided a crucial clue. The patient's travel history to the south coast of France, where WNV infections were reported, further supported the diagnosis.
While HLH secondary to flaviviruses like dengue virus is known, WNV-induced RHS is less common. The successful diagnosis and corticosteroid treatment led to clinical improvement, emphasizing the importance of recognizing WNV's potential complications. As climate change continues to impact ecosystems, the incidence of WNV infections may rise, making awareness of these rare but severe complications crucial for healthcare professionals.
The question remains: How can we better prepare for the increasing threat of WNV and its associated complications?
Note: This article is an early release and may undergo changes before its official publication. The author affiliations include Geneva University Hospitals and University of Geneva, Switzerland, and Centre Hospitalier de Wallonie Picard, Belgium.
