Histopathology and immunophenotype of acrodermatitis chronica atrophicans correlated with ospA and ospC genotypes of Borrelia species

BackgroundChronic cutaneous borreliosis (acrodermatitis chronica atrophicans, ACA) is a relatively rare manifestation of borreliosis attributed mainly to Borrelia afzelii. Chronic borreliosis has been associated with ospA and ospC genotypes. Literature on molecular investigations of Borrelia in lesions of ACA is scant. MethodsHistopathological and immmunohistochemical features in 22 biopsies of ACA (16 patients) were examined. Paraffin-embedded biopsies were analyzed with polymerase chain reaction (PCR) assays targeting ospA and ospC genes, sequencing and phylogenetic analysis. ResultsGenotyping of ospA identified B. afzelii, serotype 2, in 12 of 16 patients. ospC-PCR was positive in seven patients revealing genotypes Af5 (n=4), Af2 (n=2) and Af6 (n=1). Histopathologically, interstitial granulomatous infiltrates (CD68 positive) were common, combined with thickened collagen bundles and band-like infiltrates of CD4 positive T lymphocytes. Plasma cells were sparse/absent in 9 of 22 specimens even on staining with CD138. On CD34-staining, interstitial fibroblasts were often reduced akin to the situation in morphea. ConclusionsWith assays targeting ospA and ospC genes we confirmed from paraffin-embedded biopsies that B. afzelii, serotype 2, osp C groups Af5, Af2 and Af6 is the main cause of ACA. Specimens commonly showed a combination of band-like T-cell-rich infiltrates with interstitial granulomatous features, a pattern previously under-recognized in ACA. This finding was particularly typical for lesions infected with ospC genotype Af5.