Cutaneous borreliosis associated with T cell-predominant infiltrates: a diagnostic challenge.

BACKGROUND:With the exception of erythema migrans, Borrelia infection of the skin manifests much more commonly with B cell-rich infiltrates. T cell-rich lesions have rarely been described. OBJECTIVE:We report a series of 6 patients with cutaneous borreliosis presenting with T cell-predominant skin infiltrates. METHODS:We studied the clinicopathologic and molecular features of 6 patients with T cell-rich skin infiltrates. RESULTS:Half of the patients had erythematous patchy, partly annular lesions, and the other patients had features of acrodermatitis chronica atrophicans. Histopathology revealed a dense, band-like or diffuse dermal infiltrate. Apart from small, well differentiated lymphocytes, there were medium-sized lymphocytes with slight nuclear atypia and focal epidermotropism. An interstitial histiocytic component was found in 4 cases, including histiocytic pseudorosettes. Fibrosis was present in all cases but varied in severity and distribution. In 5 patients, borrelia DNA was detected in lesional tissue using polymerase chain reaction studies. No monoclonal rearrangement of T-cell receptor gamma genes was found. LIMITATIONS:This retrospective study was limited by the small number of patients. CONCLUSION:In addition to unusual clinical presentation, cutaneous borreliosis can histopathologically manifest with a T cell-rich infiltrate mimicking cutaneous T-cell lymphoma. Awareness of this clinicopathologic constellation is important to prevent underrecognition of this rare and unusual presentation representing a Borrelia-associated T-cell pseudolymphoma.