Background: Mycosis fungoides is the most frequent cutaneous T-cell lymphoma but has been rarely reported in children and teenagers. Although transformation into large-cell T-cell lymphoma has been described in 10% of adult cases, it is seen very rarely in children. We report here the clinical case of mycosis fungoides in a child with an unusual transformed form at presentation and treated by bone marrow allograft.

Methods: A 13 year-old boy, presenting guttate parapsoriasis for 5 years was referred to our Dermatology Department with a 2-month history of infiltrated plaques throughout the body and face. Large erythematous-squamous plaques on the trunk and face as well as a nodular lesion of the arm were also noted. On histology, typical features of mycosis fungoides were observed, in addition to transformed cells which were CD30-negative. Local treatment comprising caryolysin and dermal corticosteroids allowed initial regression of the lesions. However, a few months later, nodular lesions reappeared as well as axillary lymph nodes. Repeated histology confirmed the diagnosis of transformed mycosis fungoides with large CD30-positive cells. Despite chemotherapy, cutaneous and lymph node disease recurred, and bone marrow allograft was performed, resulting in rapid disease regression. Following the recurrence of skin lesions 2 years later, donor lymphocytes were administered in addition to treatment with interferon alpha, aiming at stimulating a graft-versus-lymphoma reaction. One year post-lymphocyte injection, the patient is in full remission.

Conclusions: This is a new case report of juvenile mycosis fungoides with unusual clinical features such as rapid course and transformed form at presentation. Juvenile mycosis fungoides represents 2.5 to 5% of cases of mycosis fungoides and transformation to large cell lymphoma is exceptional. Our case illustrates the aggressive pattern observed in some teenage patients as well as the efficacy of bone marrow allograft, most likely thanks chiefly to its graft-versus-lymphoma effect.