Cutaneous Borreliosis With a T-Cell-Rich Infiltrate and Simultaneous Involvement by B-Cell Chronic Lymphocytic Leukemia With t(14;18)(q32;q21).

Pseudolymphomatous infiltrates in Borrelia infection of the skin most commonly manifest with dense B-cell infiltrates and plasma cells. Cutaneous infiltrates of B-cell chronic lymphocytic leukemia (B-CLL) may accumulate at sites of infection, including Borrelia infection. We report an unusual constellation in a patient with synchronously diagnosed B-CLL and Borrelia infection of skin presenting with a dense dermal T-cell-rich infiltrate masking specific leukemic infiltrates of neoplastic B cells in the context of B-CLL harboring t(14;18)(q32;q21). Specific cutaneous involvement by B-CLL was confirmed by the detection of t(14;18)(q32;q21) (BCL2-IGH) using FISH in neoplastic B cells within the skin infiltrates. Borrelia burgdorferi (sensu lato) DNA detected by nested polymerase chain reaction in the skin biopsy and serological findings proved Borrelia infection. Complete resolution of the cutaneous infiltrates was observed after antibiotic treatment. This case demonstrates that Borrelia infection of the skin may present with dense T-cell-rich infiltrates mimicking cutaneous T-cell lymphoma and masking the synchronous presence of neoplastic B cells in the context of B-CLL.