Detection of clonal T-cell receptor gamma gene rearrangement with the use of PCR-DGGE for diagnosis of erythroderma.

Background. It is often difficult to establish the etiological diagnosis of erythroderma because clinical findings and immunohistology cannot always d istinguish between lymphomatous erythroderma and inflammatory erythroderma. The purpose of this work was to assess the contribution of PCR-DGGE for de tecting clonal T cell receptor gamma gene rearrangement to the etiological diagnosis of erythroderma. Patients and methods. The following inclusion criteria were used: patient w ith erythroderma; skin biopsy for histologic study, immunophenotyping and m olecular biology; minimal follow up of 12 months after initial diagnosis. T hirty patients were included from May 1, 1995 to November 30, 1998. Histolo gy slides were reread by one of the authors blinded to other data who class ed them in three categories: probable lymphoma, probable inflammatory disea se, uncertain diagnosis. Molecular data were also analyzed in the same blin ded manner. Immunohistology diagnosis was compared with the molecular data and the final diagnosis retained from clinical, histological and molecular findings as well as the disease course to last follow-up (November 1, 1999) after a mean 12 +/- 18 months follow-up. Results. Eight biopsies were classed as probable lymphomas; a T-cell clonal rearrangement of the TCR genes was detected in 7/8 cases. The one sample w ith no detectable T clone was a drug induced Sezary pseudolymphoma. The his tologial classification identified 16 cases of probable inflammatory diseas e; no clonal rearrangement of the TCR genes was found in these cases. One o f these patients had fungoid mycosis treated with caryolysin for three mont hs and developed treatment intolerance at the time of the skin biopsy. For six biopsies the histological diagnosis was "uncertain"; a clonal rearrange ment of the TCR genes was found in 2/3 of the fungoid mycosis cases and in none of the three cases of toxic dermal reactions. Discussion. This study demonstrated the contribution of genotypic analysis with PCR.DGGE to the diagnosis of erythroderma. Monoclonal TCR gene rearran gement was detected in 9/11 (82 p. 100) of the patients with lymphoma and i n 0/19 of the patients with an inflammatory dermatosis. The etiological dia gnosis of erythroderma is an excellent indication for molecular stud of ski n biopsies with PCR-DGGE.