Unmasking: paronychia as the hidden face of pemphigus.

Pemphigus vulgaris (PV) is a rare, potentially life-threatening autoimmune blistering disorder primarily affecting the skin and mucous membranes. We present a unique case of delayed diagnosis in a patient with PV, initially manifesting as isolated, extensive and therapy-resistant paronychia. PV was only considered after the appearance of mucocutaneous lesions - first oral, then cutaneous - more than 1 year after symptom onset. Diagnosis was ultimately established through histopathological examination, direct immunofluorescence and serological testing. Following diagnosis, the patient received rituximab therapy, resulting in a rapid and sustained clinical remission. This case underscores the importance of considering PV in the differential diagnosis of severe, chronic and treatment-resistant paronychia. Early recognition and diagnosis are crucial for timely intervention, which can significantly improve patient outcomes. Rituximab proved highly effective in this case, aligning with current evidence supporting its use as a first-line treatment for PV. We aim to raise awareness of atypical PV presentations and stress the need for thorough evaluation of persistent, treatment-resistant paronychia to prevent delayed diagnosis.