Linear Atrophoderma of Moulin: A Case Report Highlighting Response to Methotrexate

Abstract

Linear Atrophoderma of Moulin (LAM) is a rare dermatologic condition characterized by linear, hyperpigmented or hypopigmented atrophic lesions that follow Blaschko’s lines. Typically emerging in childhood or early adulthood, Linear Atrophoderma of Moulin remains poorly understood, with few cases reported in the literature. It is often misdiagnosed due to clinical overlap with other dermatoses, particularly Linear Morphea. While the disease is generally benign, it can cause cosmetic and functional issues. No standardized treatment exists, and therapeutic responses vary.

We report the case of a 22-year-old female who presented with a 17-year history of unilateral hyperpigmented and mildly atrophic patches on her left side, including the arm, breast, trunk, and leg. These lesions followed Blaschko’s lines and were accompanied by occasional calf pain and weakness. There was no history of inflammation, systemic symptoms, or relevant family history. Previous misdiagnoses included eczema and psoriasis, with no response to conventional treatments. A skin biopsy revealed basal layer hyperpigmentation, dermal collagen thickening, and perivascular lymphocytic infiltrates, supporting a diagnosis of Linear Atrophoderma of Moulin.

The patient was treated with oral methotrexate (20 mg weekly) and topical therapy consisting of betamethasone and calcipotriene. This treatment was maintained for one year under regular clinical monitoring.

The patient showed significant clinical improvement, including reduced calf pain, diminished weakness, and noticeable fading of hyperpigmented lesions, no new lesions developed during treatment. However, three months after discontinuation of methotrexate, new lesions appeared and symptoms recurred, highlighting the potential need for ongoing management in chronic cases.

This case emphasizes recognizing Linear Atrophoderma of Moulin as a distinct clinical entity and differentiating it from mimicking conditions such as Linear Morphea. Methotrexate, in combination with topical corticosteroid and vitamin D analog therapy, appears to offer a promising treatment option. Continued research is essential to establish effective, long-term treatment protocols.