PURPOSE: To chart clinical findings in individuals with keratitis fugax hereditaria (KFH) and the geographic distribution of their ancestors. DESIGN: A prospective cross-sectional study. METHODS: This study took place in a tertiary referral center with a cohort of 84 Finnish patients (55% female) from 25 families with the pathogenic nucleotide-binding domain, leucine-rich repeat (NLR) family pyrin domain containing 3 (NLRP3) variant c.61G>C. Observation procedures and main outcome measures were Sanger sequencing, clinical examination, corneal imaging, and a questionnaire regarding symptoms, quality of life, treatment, and comorbidities. RESULTS: The oldest members in each family were born in Ostrobothnia in Western Finland or in Southwestern Finland with historical ties to Sweden. One carrier was asymptomatic. Most (77%, 46/60) experienced their first attack between age 6 and 20 years. Three-quarters had unilateral attacks 3 to 5 times annually, primarily triggered by cold wind or air, or stress. Eighty percent (48/60) reported ocular pain (median, 7 on scale 1-10), conjunctival injection, photophobia, foreign body sensation, and tearing during attacks. Visual blur occurred in 75% (45/60) and 91% (55/60) during and after the attack, respectively, for a median of 10 days (range, 1 day-2 months). Forty-seven percent (39/60) had corneal oval opacities with irregular tomography patterns and mild to moderate decrease (20/60 or better) in best-corrected visual acuity that improved with scleral contact lenses. Except for headache in 40%, systemic symptoms were absent during the attacks. CONCLUSIONS: Symptoms and signs of KFH are restricted to the anterior segment of the eye and vary widely between individuals. We recommend scleral contact lenses as the first-line treatment for reduced vision. Allele frequencies suggest that KFH goes unrecognized in Sweden and populations with Scandinavian heritage.
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