Seasonal Hyperacute Panuveitis (SHAPU) is a destructive panuveitis of unknown cause, primarily reported in Nepal.
Since 1975, reports have accumulated from Nepal, and in 1978 Malla first described it as “endophthalmitis caused by tussock moth.” Later, Upadhyay et al. conducted detailed research and named it SHAPU.
Epidemiological characteristics are as follows:
The last major outbreak occurred from August to December 2019 (approximately 50 eyes)3). Sporadic cases have also been reported in summer of even years (May 2008, 2010, 2020), indicating that the traditional pattern of “odd years, autumn only” is changing3). Reports from Bhutan suggest a possible spread beyond Nepal1).
Although similar climatic zones exist along the Himalayas in India and Bhutan, reports are concentrated in Nepal (except for sporadic cases in Bhutan), and the reason remains unknown. It is speculated that a combination of the distribution and ecology of the suspected white moth (Gazalina species) and Nepal-specific environmental factors may be involved, but no definitive explanation has been provided.
The most characteristic feature of SHAPU is that there is almost no pain despite severe intraocular inflammation.
Intraocular pressure: Characteristically presents with low intraocular pressure (malignant hypotony) at onset.
Anterior segment and anterior chamber findings:
Posterior segment and other:
Special combined findings:
SHAPU diagnostic criteria (Kharel Sitaula et al. 2022):
Major criteria
White pupil in a congested eye: A characteristic finding observed from the early stage of onset.
Painless/mild pain: Pain is minimal despite severe inflammation.
Almost always unilateral: Bilateral cases are extremely rare.
Rapid vision loss: Severe visual impairment within a short time.
Minor criteria
Malignant hypotony: Low intraocular pressure (IOP <10 mmHg).
Mainly in children: The majority of patients are children.
Hypopyon and fibrinous exudate: Exudative changes in the anterior chamber.
Mydriasis difficulty and invisible fundus: Difficulty in evaluating the posterior segment due to inflammation.
Because there is almost no pain, parents or patients may not recognize the severity of the symptoms, leading to delayed consultation. However, inflammation progresses rapidly, and by the time of consultation, two-thirds of patients are already blind. If left untreated, it can lead to phthisis bulbi. The combination of painless redness, white pupil, and vision loss is a warning sign that should strongly suggest SHAPU.
Contact with or exposure to white moths (Gazalina species, Nepali name “Seto Putali”) is established as the greatest risk factor.
Moth life cycle and seasonality:
Moths (genus Gazalina) are commonly found at altitudes above 2,000 m and are observed in Nepal from March to October 1). Their life cycle is as follows 3).
In odd-numbered years, adults emerge in large numbers in autumn (August to December), causing major outbreaks. Sporadic cases in even-numbered years are explained by unhatched eggs hatching and developing into adults under favorable conditions such as rising temperatures, rainfall, and increased humidity 3).
The following table shows the differences between odd-year and even-year types.
| Feature | Odd-year type (autumn) | Even-year type (summer) |
|---|---|---|
| Onset period | August to December | Around May to June |
| Scale | Large outbreak | Sporadic cases |
| Corneal complications | Few | Many (including corneal melting) |
| Severity | Relatively uniform | More severe, poor treatment response |
It is possible. The abdominal hair tufts of moths easily detach and float in the air, so they can adhere to the ocular surface even without direct contact. In fact, about half of SHAPU patients have no history of direct contact with moths and develop the condition only through indirect exposure (e.g., being in the same space)3).
SHAPU has no established diagnostic biomarkers, and clinical diagnosis is fundamental. Since delayed diagnosis directly affects prognosis, testing should be initiated promptly in suspicious cases.
This is the most important procedure to be performed in all suspected cases.
Performed in all cases. Useful for evaluating the extent of vitreous opacity and confirming the presence of shallow inferior retinal detachment 1, 2, 3).
Differentiation from the following diseases is important.
| Disease | Key points for differentiation from SHAPU |
|---|---|
| Exogenous/endogenous endophthalmitis | Excluded by immunocompetent patients, no history of surgery or trauma, and negative culture 1) |
| Ophthalmia nodosa | Chronic granulomatous inflammation caused by moth hairs. Slow onset, localized, and rarely associated with acute vision loss1) |
| Vogt-Koyanagi-Harada disease | Bilateral, granulomatous keratic precipitates, with skin and hair involvement |
| Endogenous bacterial endophthalmitis | Positive for systemic infection focus (bacteremia) |
There is currently no established standard treatment protocol for SHAPU. The following are current management approaches compiled from case reports.
Topical eye drops (all cases):
Systemic administration:
Core vitrectomy: This is the main treatment, and it is recommended to be performed within 24 hours of presentation.
Intravitreal injection (after vitrectomy):
Subconjunctival injection:
Special administration (in cases with scleritis):
Early core vitrectomy and intravitreal injection can lead to good outcomes in some cases (reported examples: vision HM → 6/63), hand motion → 6/602)). However, many severe cases or those with delayed treatment progress to phthisis bulbi. In even-year type, 2 out of 3 cases developed phthisis bulbi3). Surgical intervention within 24 hours of presentation is key to preserving vision.
The pathogenesis of SHAPU remains unknown, and several hypotheses have been proposed.
Leading hypothesis: Microtrauma to the ocular surface caused by moth setae (hairs) → introduction of microorganisms/toxins/allergens → inflammatory cascade3). The rapid onset of symptoms suggests a cytokine storm due to a type I allergic reaction3).
Intrastromal follicles (structures thought to be moth hairs) have been identified in the corneal stroma of some cases, but this finding is not observed in many cases and is not universal.
Debate on infectious versus non-infectious etiology:
Culture and staining results have been consistently negative across multiple case series, and no specific microorganism has been established as the causative agent1, 2, 3). Although microorganisms have been isolated in some cases, the possibility of secondary infection cannot be ruled out. A previous report found a high rate of Anellovirus detection in vitreous fluid, but this has not been replicated.
A leading hypothesis is that moths act as vectors (carriers that transport microorganisms/toxins/allergens to the ocular surface)3).
The existence of a case with scleritis (a trekker at an altitude of 4,371 m) demonstrates the ability of inflammation to spread beyond uveal tissue, adding a new aspect to the pathophysiology of SHAPU1). Although usually painless, the case with scleritis presented with severe pain, indicating variation in the disease presentation1).
Animal experiments (guinea pigs, rabbits) have not been able to reproduce the disease, making it difficult to elucidate the pathophysiology.
In 2025, a case of SHAPU onset was reported at Pheriche (Nepal), at an altitude of 4,371 m 1). Previously, SHAPU was thought to be limited to temperate to subalpine zones at altitudes of 1,000–3,000 m, but this suggests that the habitat of the Gazalina moth may be higher than assumed. Additionally, this is the first report of a case complicated with necrotizing scleritis, revealing that the pathology of SHAPU can involve pan-ophthalmitis.
In the report by Sitaula et al. (2025), no light perception (NPL) persisted one year after onset, and phthisis bulbi was progressing 1). This case was an adult (27 years old), further demonstrating that SHAPU, which is more common in children, can also occur in adults.
Gurung et al. (2021) reported three cases that developed in May 2020 (summer of an even-numbered year) and showed that the even-year type is more severe and has a poorer treatment response than the odd-year type 3). Two of the three cases (66.6%) progressed to phthisis bulbi, and one of them was the first reported case of corneal melting.
The mechanism of severity in the even-year type and its biological differences from typical large outbreaks remain unknown, and are topics for future research.
In the histopathological findings of the iris in a high-altitude case reported by Sitaula et al. (2025), focal areas of exudates were observed 1). This is the first histological report for SHAPU, but the findings were nonspecific and of limited diagnostic value.
The epidemiological association with moths (genus Gazalina) has been established in multiple studies, but the specific pathogenesis remains unknown. Hypotheses involving toxins, allergens, and microbial vectors have been proposed, but none have been confirmed. The consistently negative culture results argue against an infectious etiology, but a non-infectious cause has not been definitively established 1, 2, 3). Reproduction in animal models is also difficult, and further research is needed for clarification.
Sitaula RK, Karki P, Poudel P, Jha P, Bhusal DR, Sharma AK, et al. Seasonal Hyperacute Panuveitis from the highest reported altitude: co-occurrence with scleritis - an unusual presentation. BMC ophthalmology. 2025;25(1):484. doi:10.1186/s12886-025-04316-0. PMID:40855287; PMCID:PMC12379537.
Karki P, Kharel Sitaula R, Khatri A, et al. Challenges of Pediatric Cataract Surgery in a Case of Seasonal Hyperacute Panuveitis (SHAPU). Case Reports in Ophthalmological Medicine. 2021;2021:5591859. doi:10.1155/2021/5591859.
Gurung H, Kharel Sitaula R, Karki P, et al. Sporadic summer outbreak of SHAPU in even years: Does the pattern match with the usual autumn outbreak? American Journal of Ophthalmology Case Reports. 2021;24:101198.
