Atypical lymphocytic lobular panniculitis: A clonal subcutaneous T-cell dyscrasia

Background: Atypical lymphocytic lobular panniculitis (ALLP) is a recently described entity characterized by waxing and waning plaques. A morphologic and biologic continuum with subcutaneous panniculitis-like T-cell lymphoma has been suggested. Methods: Between 2003 and 2007, we encountered five patients with ALLP. Comprehensive phenotypic and molecular studies were performed using multiplex polymerase chain reaction. Results: The patient population comprised four women, one man and two boys, age range of 6-42 years. All patients had a similar clinical presentation, being one of the recurrent infiltrative plaque-like lesions. All cases showed a permeation of the interstitial spaces of the subcutis by well-differentiated lymphocytes unaccompanied by significant fat necrosis. Molecular studies showed a clonal and/or oligoclonal profile in all cases. In all cases in which multiple biopsies were obtained, there was preservation of the identical T-cell clonotypes at different biopsy sites and over time. No patient progressed to lymphoma. One patient achieved remission with isotrentinoin. Conclusions: ALLP represents a form of cutaneous lymphoid dyscrasia given the relatively self-limited nature of the eruption, albeit in the context of clinical recurrence.