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- Presentation
Lupus Mimickers and Diagnostic Pearls: Lupus Paniculitis, SPTCL, and Secondary Syphilis
Description
The talk presented two dermatology cases that highlight lupus mimickers and diagnostic pitfalls. In the first case, a woman with longstanding systemic and discoid lupus developed tender subcutaneous nodules and plaques consistent with lupus paniculitis, including breast involvement that mimicked breast cancer on imaging and led to extensive biopsies; the speaker emphasized lupus paniculitis as a cause of lipoatrophy and stressed communication across dermatology, primary care, and oncology. When the patient later developed unusual distal leg plaques, repeat biopsy showed atypical alpha-beta T-cell infiltrates with clonality, leading to a diagnosis of subcutaneous panniculitis-like T-cell lymphoma (SPTCL), underscoring that patients can have more than one diagnosis and that unusual features should prompt reevaluation. The speaker noted that alpha-beta SPTCL generally has an indolent course and can respond to immunomodulatory therapy, unlike gamma-delta T-cell lymphoma. In the second case, a woman with annular scaly plaques, facial and palm involvement, a lupus-suggestive biopsy, positive ANA, anticardiolipin antibodies, and a very high RPR was ultimately diagnosed with secondary syphilis rather than cutaneous lupus. Key pearls included that lupus-related false-positive RPRs are usually low titer, palm involvement strongly suggests syphilis, facial SCLE often suggests a drug-induced process, and spirochete staining can confirm the diagnosis. Her lesions improved dramatically with penicillin.
View moreConclusions
- Lupus paniculitis can closely mimic malignancy, especially breast cancer, so biopsy and close interdisciplinary communication are essential to avoid unnecessary oncologic workups and treatment.
- Patients with lupus can develop more than one simultaneous disease, and unusual lesions should prompt reconsideration of the initial diagnosis rather than assuming all findings are due to lupus.
- Subcutaneous panniculitis-like T-cell lymphoma should be suspected when panniculitis is atypical, and alpha-beta SPTCL generally has an indolent course with a favorable prognosis compared with gamma-delta T-cell lymphoma.
- False-positive RPR results can occur in lupus because antiphospholipid antibodies cross-react with non-treponemal test antigens, but these false positives are usually low titer.
- A very high-titer RPR should not be dismissed as lupus-related serologic noise and instead should raise strong concern for true syphilis requiring treatment.
- Secondary syphilis can mimic subacute cutaneous lupus, particularly when lesions involve the face and palms, which are unusual sites for SCLE.
- Drug-induced SCLE should be considered when facial involvement is present, since that distribution is often a clue to medication-triggered disease.
- Using the full clinical pattern, serology, and pathology together is crucial for distinguishing autoimmune skin disease from infectious mimickers and preventing misdiagnosis.
- Sontheimer RD, Thomas JR, Gilliam JN. Subacute Cutaneous Lupus Erythematosus: A Cutaneous Marker for a Distinct Lupus Erythematosus Subset. Arch Dermatol. 1979;115(12):1409-1415.#10.1001/archderm.1979.04010120007006
- Guitart J, et al. Clinical and Pathological Characteristics and Outcomes Among Patients With Subcutaneous Panniculitis-like T-Cell Lymphoma and Related Adipotropic Lymphoproliferative Disorders. JAMA Dermatology, 2023.#10.1001/jamadermatol.2022.3347
- Ghanem KG, Ram S, Rice PA. The Modern Epidemic of Syphilis. N Engl J Med. 2020 Feb 27;382(9):845-854.#10.1056/nejmra1901593
- Two-Stage Syphilis Testing. JAMA Diagnostic Test Interpretation. Published online June 14, 2024.#10.1001/jama.2024.10505