Background: Erythroderma is a diffuse, inflammatory skin reaction that, in rare instances, is associated with hematologic malignancies such as cutaneous T-cell lymphoma (erythrodermic mycosis fungoides) or T-cell leukemia (Sezary syndrome or adult T-cell leukemia/lymphoma).
Observations: We screened 30 patients with erythroderma (20 patients with erythroderma of known etiology and 10 patients with idiopathic erythroderma) for the presence of circulating monoclonal T-lymphocyte populations using T-cell receptor (TCR)-gamma gene-specific polymerase chain reaction and automated capillary DNA electrophoresis. Moreover, the phenotypic analysis of peripheral blood CD4+ lymphocytes was performed using the following surface markers: CD3, CD7, CD8, CD25, CD26, CD27, CD28, CD29, CD30, CD45RO, CD45RA, CD56, CD134, HLA-DR, TCRalphabeta, TCRgammadelta, and cutaneous lymphocyte antigen (CLA). In 5 patients with idiopathic erythroderma we detected T-cell clones in peripheral blood (in 1 case, associated with the presence of the same clone in the skin) and a 2-fold increase in the proportion of CD3+ CD4+ CD7- CD26- cells. Cell depletion studies indicated that the monoclonal T cells were present within the CD4+ CD7- cell population. Clinically, all patients had chronic, recalcitrant erythroderma but none developed any hematological malignancy during their lifetimes or fulfilled the criteria for cutaneous lymphoma or Sezary syndrome.
Conclusions: A proportion of patients with chronic erythroderma present with the monoclonal expansion of CD4+ CD7- CD26- lymphocytes in their blood. This condition represents a probably benign T-cell dyscrasia, or one of very low malignancy. Alongside monoclonal gammapathy of undetermined significance (MGUS) and monoclonal (B-cell) lymphocytosis of undetermined significance (MLUS), we propose using monoclonal T-cell dyscrasia of undetermined significance (MTUS) to underline a conceptual similarity between this disorder and the more common types of lymphocytic dyscrasia.