Purpose <p>Median canaliform dystrophy of Heller (MCDH) is a rare nail matrix disorder typically affecting one or both thumbnails. Multinail involvement, including toenails, is rarely reported. We describe a case with atypical multi-digit involvement to broaden the recognized clinical spectrum.</p> Methods <p>A 29-year-old male underwent dermatologic evaluation for chronic, asymptomatic nail deformities of both thumbnails and the left great toenail. Diagnosis was made clinically based on characteristic morphology and exclusion of major clinical mimickers, including habit-tic deformity, inflammatory nail disorders, and clinically evident onychomycosis.</p> Results <p>Examination revealed central longitudinal canals with symmetric oblique lateral ridging forming a fir-tree pattern. Periungual tissues were normal, and there was no history of trauma, habitual manipulation, major psychological stressor temporally associated with lesion onset or progression, systemic disease, or medication exposure. A clinical diagnosis of MCDH was established. The patient was managed conservatively with reassurance and advice to avoid microtrauma. At 6-month follow-up, the nail changes remained clinically stable, with no appreciable improvement or progression, and the patient remained asymptomatic.</p> Conclusion <p>This case demonstrates an uncommon idiopathic presentation of MCDH involving bilateral thumbnails and a toenail. Awareness of such atypical presentations may improve recognition, reduce misdiagnosis, and help avoid inappropriate treatment or unnecessary invasive procedures.</p>