Atypical Facial and Scalp Lupus Erythematosus Tumidus: Diagnostic Challenges from Long-Term Misdiagnosis and Conflicting Histopathology.

BACKGROUND: Lupus erythematosus tumidus (LET) is a rare photosensitive skin lupus subtype. Its erythematous swelling easily mimics erysipelas, cellulitis or herpes zoster, leading to frequent misdiagnosis. Atypical cases complicated by interface dermatitis and patient self-medication create prominent differential diagnostic difficulties. CASE PRESENTATION: A 58-year-old woman had scalp and facial erythema swelling for 1 year, worsened over 4 days. She was repeatedly misdiagnosed with bacterial infectious skin diseases and given ineffective antibiotics. Before admission, she took herbal decoctions and received bloodletting acupuncture by herself, aggravating facial edema. Examination showed infiltrative erythema and scalp alopecia. Full autoantibody, complement and routine lab tests were nearly normal. Cheek biopsy showed typical LET mucin deposition and periadnexal lymphocytic infiltration, while scalp biopsy unexpectedly revealed focal basal liquefaction degeneration. The final diagnosis of atypical LET was made after comprehensive clinicopathological evaluation. Combined hydroxychloroquine and methylprednisolone therapy induced obvious lesion remission within 6 months of follow-up. CONCLUSION: This atypical LET case illustrates key differential diagnostic traps caused by long-term misdiagnosis and conflicting pathological findings. Unsupervised herbal treatment and blood-letting acupuncture disturbs clinical manifestations and delays formal therapy. For patients presenting with facial edematous erythema accompanied by atypical epidermal pathological changes, comprehensive serological screening and thorough histopathological examination are warranted. Early clinicopathological combined diagnosis, antimalarial drugs and strict sun protection help avoid misdiagnosis and recurrence.