The diagnostic challenge of Microsporidium keratoconjunctivitis: Case reports and literature review

The purpose of the study was to review the current medical evidence on Microsporidium keratoconjunctivitis (MKC) and to illustrate its clinical presentation, diagnostic challenges, and management through case reports. A comprehensive literature review was conducted using Google Scholar, PubMed, Scopus, and Embase to identify and synthesize available evidence on microsporidial keratoconjunctivitis, focusing on epidemiology, risk factors, clinical features, diagnostic methods, and treatment outcomes. In addition, two cases of MKC in immunocompetent young adults are presented to highlight common diagnostic challenges and clinical management. The literature consistently characterizes MKC as an uncommon but increasingly recognized cause of acute keratoconjunctivitis, frequently mistaken for viral or other nonspecific inflammatory entities. The disease typically presents with unilateral, multifocal, grayish-white corneal epithelial and subepithelial infiltrates, often associated with a follicular conjunctival response. Across published studies, delayed recognition and prior exposure to topical corticosteroids are recurrently linked to clinical deterioration. In our case series, initial misdiagnosis led to persistent or worsening symptoms despite corticosteroid or supportive therapy. Following initiation of topical 0.5% moxifloxacin monotherapy, both patients demonstrated prompt resolution of corneal lesions, complete visual recovery, and no evidence of recurrence. Microsporidiosis should be considered in the differential diagnosis of atypical keratoconjunctivitis that resembles viral infections, particularly when characteristic corneal lesions are present, and symptoms worsen with corticosteroids or do not improve with standard supportive therapy. Prompt recognition and appropriate management are crucial to prevent disease progression. Although fluoroquinolone monotherapy has been recommended and proved effective in these two cases, no established therapeutic regimen currently exists.