The diagnostic assessment of cutaneous T-cell infiltrates is problematic for dermatopathologists. A variety of conditions, including lymphomatoid hypersensitivity reactions and lymphomatoid lupus erythematosus, can demonstrate lymphoid atypia and phenotypic changes that can mimic cutaneous T-cell lymphoma (CTCL). A similar issue revolves around lymphoid dyscrasias, which includes parapsoriasis, atypical pigmentary purpura, pityriasis lichenoides chronica, indeterminate lymphocytic lobular panniculitis, and lymphomatoid papulosis, which can progress to CTCL. A reverse transcription (RT) in situ PCR assay for T-cell receptor beta rearrangements (TCRbeta) was used to assess T-cell clonality in formalin-fixed, paraffin-embedded tissues. In 7 of 8 cases of classic CTCL, the RT in situ PCR assay for TCRbeta rearrangement showed monoclonality; the other was biclonal. Further, in cases with multiple lesions over time, the same T-cell clone could be detected including in those patients whose biopsies showed large-cell transformation. Monoclonality was also demonstrated in each of 2 cases of cutaneous lymphomatoid papulosis. Demonstration of oligoclonality (and one case of biclonality) by RT in situ PCR was confined to those cases that either represented prelymphomatous conditions such as large plaque parapsoriasis or pityriasis lichenoides or lesions of drug-induced lymphomatoid hypersensitivity that all demonstrated clinical regression. In conclusion, RT in situ PCR for TCRbeta, which can be done on formalin-fixed biopsies and allows direct correlation of the molecular data with the histology, is a useful adjunctive test in the differentiation of CTCL from its mimics.
Mycobacterium marinum is an atypical mycobacterium predominant in aquatic environments that can be acquired by contact with contaminated water, causing skin infections or, less commonly, deeper infection of tendons and joints. Although M. marinum has been recognized as a mimicker of inflammatory arthropathy (1-4), the diagnosis of infection requires a high index of suspicion and is often delayed, resulting in unsuccessful regimens of immunosuppression and a prolonged clinical course. We present a case of M. marinum-induced tenosynovitis with cutaneous manifestations, which at first was highly suggestive of rheumatoid arthritis (RA) until the use of musculoskeletal ultrasound (MSK-US) by a rheumatologist brought that diagnosis into question and appropriately delayed immunosuppressive therapy. Subsequent work-up including biopsy and culture of a skin lesion differentiated the correct infectious diagnosis from inflammatory arthropathy, and ensured appropriate antibiotic treatment in a timely fashion.A 53-year-old man was referred to our rheumatology office for evaluation of a subacute asymmetric polyarthropathy, predominantly affecting the right metacarpophalangeal (MCP) joints. Two months prior to presentation, the patient palpated a nodular subcutaneous mass proximal to his right dorsal second MCP, with subsequent development of swelling and pain of that MCP. Naproxen and a brace provided partial relief, but the swelling and pain spread to other MCP joints, to some proximal interphalangeal (PIP) joints, and the wrists, predominantly of the right side. He had difficulty making a fist, and the stiffness was significantly worse each morning for hours. Review of systems was negative for fever, weight loss, skin rash, alopecia, oral ulcers, dry eyes, dry mouth, photosensitivity, Raynaud's phenomenon, or constitutional symptoms.The patient's past medical history was unremarkable. His only medication was naproxen. He had no drug allergies. The patient had no history of tobacco smoking, alcohol or drug abuse, or any family history of autoimmune disease or inflammatory arthritis.On examination, the patient had substantial swelling and tenderness of the right second, third, and fifth MCP joints, with limited flexion of all digits, but no swelling or
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