Febrile ulceronecrotic Mucha-Habermann disease (FUMHD) is a severe variant of pityriasis lichenoides et varioliformis acuta (PLEVA). PLEVA patients only very rarely have systemic signs; the cutaneous lesions are usually asymptomatic, but may be pruritic and may heal with scarring. FUMHD often starts out as classic PLEVA, but goes on to develop widespread ulceronecrotic lesions and is associated with a high mortality rate. Whether Pityriasis lichenoides chronica (PLC) and PLEVA form a spectrum rather than single entities of clonal lymphoproliferative diseases has been discussed. Recently, it has been proposed that FUMHD, too, is a clonal lymphoproliferative disorder. Here, we report two cases of FUMHD with monoclonal T-cell population, as detected by Southern blot analysis. We propose that clonal FUMHD represents a cutaneous T-cell lymphoma entity.