Abstract
35-year-old African-American woman with a history of Graves’ disease treated with radioactive iodine ablation, presented with fatigue, weakness, and new subacute pruritic rash. Patient previously seen by dermatology for treatment recalcitrant pretibial myxedema. Her new dermatologic findings were confluent, well-demarcated, hyperpigmented, scaling plaques with an erythematous border on the bilateral upper and lower extremities. Onset was one month ago, it started as a small dark spot on the distal lower extremity. She endorsed increased bilateral lower extremity swelling, left eye ptosis and blurry vision. Patient endorsed nonadherence to levothyroxine for months, and only restarted her medication a few weeks ago. Laboratory work-up notable for transaminitis, elevated thyroid stimulating hormone (TSH) 76, decreased free T4 0.91, and elevated autoantibodies associated with Graves’ disease (thyroid stimulating immunoglobulin antibody 11.50, TSH receptor antibody 21.50). Surgical pathology revealed prominent hyperkeratosis and parakeratosis with heavy pigmentation of the stratum corneum due to melanin incontinence. The epidermis showed mild papillomatosis. A dermal pattern of significant mucin deposition was also present. The dermal changes are compatible with dysthyroid myxedema, however the etiology for the epidermal change is unknown, as the epidermis is usually normal or slightly thickened in pretibial myxedema. The authors propose that the patient could have presented with plaque-like myxedema with exaggerated pigment incontinence due to her Fitzpatrick skin type. This case presents an unusual histopathological epidermal change in pretibial myxedema, with a striking clinical manifestation.