Seasonal Hyperacute Panuveitis (SHAPU): A Review of the Current Aetiological Theories and Future Direction of Research and Therapeutics

Seasonal Hyperacute Panuveitis (SHAPU) is a rapidly progressive, vision-threatening inflammatory eye disease reported exclusively in Nepal, with occasional suspected cases in neighbouring regions. Despite its initial recognition in 1975, the aetiology remains unknown, and outbreaks continue to occur predominantly in the autumn of odd-numbered years, although smaller summer events have been described. SHAPU affects both adults and children, with a higher prevalence among paediatric populations, and can lead to irreversible blindness within days if untreated. This literature review synthesises over 50 years of epidemiological, clinical, and mechanistic studies to evaluate current theories on SHAPU’s causation and to highlight avenues for future research. Proposed aetiologies include infectious agents, immune-mediated mechanisms, vector-borne or toxin exposures, and environmental or climatic triggers, yet none have been definitively proven. The review also examines diagnostic challenges, including the potential for misdiagnosis as endophthalmitis, and discusses advances in metagenomic sequencing and immunological profiling that may improve detection and understanding of the disease. Finally, it identifies key gaps in surveillance, reporting, and multidisciplinary research, advocating for systematic data collection, collaborative investigations, and international awareness to mitigate the substantial clinical and societal burden of SHAPU.