Cutaneous T cell lymphoma complicating severe atopic dermatitis. Is making a diagnosis the main challenge?

The association between severe long-term atopic dermatitis (AD) and the risk of skin lymphoma is still a matter of debate, since epidemiological studies have shown contradictory results. We report 2 cases of patients with a documented history of severe longstanding atopic disease, who had never been treated with topical or systemic calcineurin inhibitors, and who developed a cytotoxic cutaneous T cell lymphoma (CTCL). For these 2 patients, clinical manifestations preceded the diagnosis of CTCL. The diagnosis was based on histological findings and molecular analysis of the T cell receptor (TCR) clonality. These cases illustrate the difficulty in diagnosing CTCL in patients with severe AD and extensive inflammatory skin lesions. The transition between severe AD and CTCL is progressive; histological findings and molecular evidence of TCR clonality are detected after the clinical changes. These 2 cases lend further support to the hypothesis of an association between severe long-term AD and CTCL.