Scleromyxoedema and Thyroid Disease: A Case Report.

Scleromyxoedema (SM) is a rare cutaneous mucinosis characterised by waxy papules, diffuse skin induration, and systemic involvement such as gastrointestinal, cardiopulmonary, or neurological complications. The disease is strongly linked to the presence of monoclonal gammopathy. Traditionally, thyroid dysfunction is considered an exclusion criterion for the diagnosis of SM; however, clinical observations suggest that this association may occur in certain cases. We present the case of a 70-year-old woman with a history of hypothyroidism on levothyroxine for three months, who presented with progressive cutaneous sclerosis affecting the face, trunk, and limbs, along with dysphagia for solid food. Clinical examination revealed generalised induration of the skin and limited mouth opening. Skin biopsy confirmed the diagnosis of SM, revealing fibroblast proliferation and mucin deposition. Laboratory tests identified a monoclonal immunoglobulin G kappa gammopathy, elevated free kappa light chains, and persistent hypothyroidism with high levels of anti-thyroid peroxidase antibodies, which confirmed the diagnosis of Hashimoto's thyroiditis. Liver abnormalities and biopsy findings were consistent with primary biliary cholangitis. The patient was treated with systemic corticosteroids and intravenous immunoglobulin (IVIG), but no clinical improvement was observed. The disease progressed, and she died five months after the last treatment cycle. This case illustrates the rare coexistence of SM and autoimmune thyroid disease, raising questions about whether thyroid dysfunction should systematically exclude SM diagnosis. The differential diagnosis with hypothyroid myxedema and systemic sclerosis is crucial, as their histopathological features differ significantly. Although IVIG is first-line therapy for SM and achieves good response rates in many cases, therapeutic failure, as seen here, highlights the need for further research into optimal treatment strategies for SM with overlapping autoimmune conditions.