The Clonality Conundrum: Navigating Diagnostic Challenges in Discoid Lupus Erythematosus

Summary: Discoid lupus erythematosus (DLE) is the most common cutaneous lupus subtype. Clonal T-cell receptor (TCR) gene rearrangements, a hallmark of T-cell lymphoma, can aid in diagnosis of ambiguous cases. However, TCR clonality may rarely occur in chronic inflammation or autoimmune disorders, complicating diagnosis. A 78-year-old female with a 20-year history of DLE presented with scalp nodules, scarring alopecia, and erythema. Biopsy showed increased dermal lymphoid infiltrate, predominantly CD4+ T cells, without significant T antigen aberrancies or epidermotropism. PCR studies revealed clonal TCR beta gene rearrangement. No clonal TCR gamma gene rearrangement was detected. She responded well to a year of intralesional and topical corticosteroids, achieving a stable and improved skin condition. Alterations in the TCR repertoire are found in multiple autoimmune diseases, including lupus and rheumatoid arthritis. TCR-gene rearrangement studies are valuable for distinguishing abnormal T-cell proliferations from reactive processes. However, the detection of a clonal TCR-gene rearrangement is not necessarily synonymous with the presence of a T cell neoplasm. The results of clonal TCR-gene rearrangements in patients with autoimmune diseases should be interpreted with caution. Clinical correlation is essential to avoid overdiagnosis of T-cell lymphoma.