New study reveals long delays and misdiagnoses in a rare eye disease common in Finland and Sweden

About half of those affected eventually develop lasting cloudiness in the cornea, impairing vision. KFH is caused by a single genetic variant in the NLRP3 gene and is passed down in families. Although the condition was first described in 1964, and its genetic cause was found in 2018, many healthcare professionals are still unfamiliar with it.

In this study, researchers reviewed the medical records of 96 Finnish patients who had a confirmed genetic diagnosis of KFH. They also examined 2,010 DNA samples from two Finnish biobanks, focusing on people who had been diagnosed with eye inflammations often mistaken for KFH, such as iritis (anterior uveitis), herpes keratitis, and other forms of corneal inflammation or clouding.

Findings revealed that 40% of patients with KFH were initially misdiagnosed with anterior uveitis, 14% with conjunctivitis, and 13% with recurrent corneal erosion. The median time to correct diagnosis was 19 years, with some cases taking up to 62 years. About 0.6% of people diagnosed with iritis in the biobank data actually carried the gene defect that causes KFH.

These results highlight a clear need for greater awareness of KFH among eye doctors and other healthcare professionals, especially in countries like Finland and Sweden, where the condition is more common. The researchers suggest that adding genetic testing for the NLRP3 variant in patients with unexplained or unusual eye inflammation could improve diagnostic accuracy and help avoid unnecessary treatments. Getting the correct diagnosis early on is essential — not just for managing symptoms but also for giving patients clarity and peace of mind.

Original article:
Errors and Delays in Diagnosing Keratitis Fugax Hereditaria.
Immonen AT, Kawan S, Backlund MP, Saaren-Seppälä H, Kivelä TT, Turunen JA. American Journal of Ophthalmology. 2025.