Coexistence of Riehl's Melanosis, Lupus Erythematosus and Thyroiditis in a Patient.

Introduction: Riehl's melanosis (RM) is an acquired hyperpigmentation disorder, presenting diffused and reticulate brownish-gray pigmentation, preferentially on the face and neck. RM overlaps with systemic lupus erythematosus (SLE) and Hashimoto's thyroiditis has never been reported. Case: We report a case of RM patient accompanied with SLE and Hashimoto's thyroiditis of primary hypothyroidism. Progressing, diffuse, symmetric, and reticular hyperpigmentation was seen on the face, neck, and upper limbs, manifesting as typical melanosis. Skin microscopy showed diffuse black-pepper-like changes and telangiectasias. The diagnosis of SLE and primary hypothyroidism were confirmed by follow-up investigations. The hyperpigmentation turned notably lighter after 14 months of treatment with prednisone, hydroxychloroquine, and L-thyroxine. Discussion: The exact pathogenesis of RM is unclear and exposure to coal tar dyes, ultraviolet, and fragrance fixatives in cosmetics are believed to be contributing factors, while some cases involve no triggers. It is not impossible that RM is a rare skin manifestation of SLE that has never been reported. The skin hyperpigmentation in this patient was not triggered by thyroid disease. Conclusion: RM could be a skin manifestation of autoimmunity. Coexistence of RM, lupus erythematosus and thyroiditis in the same patient is rare and has never been reported.