Linear Interstitial Keratitis - Assessment of a Poorly Explored Clinical Entity

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Purpose: This retrospective, single-center case series included four patients clinically diagnosed with linear interstitial keratitis at the University Hospital Zurich, Switzerland.We aimed to expand the existing knowledge on this rare clinical entity. Observations:We obtained data on patient demographics, laboratory assessments, medical and surgical treatment, and patient outcomes.All four patients aged 21 and younger reported a sudden onset of painful red eye and were referred to our tertiary care hospital because of suspected unilateral infectious keratitis.For each patient, we performed diagnostic corneal swabs for common bacteria, fungi, and viruses, all of which were inconclusive.We further assessed autoimmune serological markers and screened for HIV, hepatitis B and C, and syphilis.In Case 2, we performed in-vivo confocal microscopy.While infectious screening was negative, we detected antinuclear antibodies in two out of four patients (Cases 2 and 3).Rheumatology consultation found no underlying autoimmune disease in all patients.Treatment mainly included topical antibiotics, corticosteroid eye drops and lubrication, and additional systemic valaciclovir coverage in two patients (Cases 1 and 4).The outcomes depended on the severity of the initial presentation as well as the management of the recurrences. Conclusions and Importance:Linear interstitial keratitis remains a poorly explored entity, preferably affecting adolescent patients.We recommend that future investigations include autoimmune workup to reveal unknown causal relationships.Long-term patient follow-up is paramount to detect disease recurrence and activity, finally minimizing the risk for corneal perforation.