Clonal cutaneous and neurosyphilis: A pitfall in pseudolymphoma diagnosis

Syphilis is a sexually transmitted infectious disease caused by the bacterium Treponema pallidum and can cause a wide variety of cutaneous manifestations, most commonly, a papulosquamous eruption of the trunk and extremities. Treatment with penicillin is curative. We report a case of a 69‐year‐old man who presented with recent onset of blurry vision and a nonpainful, nonpruritic eruption of pink‐to‐violaceous dermal nodules on his upper trunk and upper extremities. Biopsies of two separate locations revealed a dense superficial and deep perivascular atypical lymphocytic infiltrate with admixed plasma cells, histiocytes, and eosinophils. Some scattered cells expressed CD30, PD1, BCL‐6, and ICOS. T‐cell receptor (TCR)‐rearrangement showed an identical TCR‐gamma clone between both biopsy specimens. The patient was subsequently seen by ophthalmology and diagnosed with acute anterior uveitis. Rapid plasma reagin was reactive and cerebrospinal fluid studies showed findings consistent with a diagnosis of neurosyphilis. A T. pallidum immunostain of the skin biopsies was performed upon re‐review, and was diffusely positive for spirochetes at the dermal‐epidermal junction and within injured vessels. The patient was treated with penicillin G with near‐resolution of his skin lesions. This case highlights the unusual ability of syphilis to mimic a T‐cell lymphoma with matching clones across two different biopsy sites.