Our patient demonstrated all 3 aspects of the Diamond triad: PTM, exophthalmos, and acropachy. Patients present with all 3 features in less than 1% of reported cases of Graves disease.3 Although all 3 features are seen together infrequently, thyroid dermopathy and acropachy often are markers of severe Graves ophthalmopathy. In a study of 114 patients with Graves ophthalmopathy, patients who also had dermopathy and acropachy were more likely to have optic neuropathy or require orbital decompression.4
After overcoming the diagnostic dilemma that the elephantiasic presentation of PTM can present, therapeutic management remains a challenge. Heyes et al5 documented the successful treatment of highly recalcitrant elephantiasic PTM with rituximab and plasmapheresis therapy. In this case, a 44-year-old woman with an 11-year history of Graves disease and elephantiasic PTM received 29 rituximab infusions and 241 plasmapheresis treatments over the course of 3.5 years. Her elephantiasic PTM clinically resolved, and she was able to resume daily activities and wear normal shoes after being nonambulatory for years.5
Rituximab is a monoclonal antibody against CD20, a protein found primarily on the surface of B-cell lymphocytes. Although rituximab initially was approved by the US Food and Drug administration for the treatment of malignant lymphoma, it has had an increasing role in the treatment of autoimmune disorders such as rheumatoid arthritis. Rituximab is postulated to target B lymphocytes and halt their progression to plasma cells. By limiting the population of long-lasting, antibody-producing plasma cells and decreasing the autoantibodies that cause many of the symptoms in Graves disease, rituximab may be an effective therapy to consider in the treatment of elephantiasic PTM.6
Although the exact mechanism is poorly understood, PTM likely is a sequela of hyperthyroidism because of the expression of thyroid-stimulating hormone receptor proteins found on normal dermal fibroblasts. Thyroid-stimulating hormone receptor autoantibodies are thought to stimulate these fibroblasts to produce glycosaminoglycans. Histopathologically, accumulation of glycosaminoglycans deposited in the reticular dermis with high concentrations of hyaluronic acid is observed in PTM.7
Treatment of elephantiasic PTM remains a therapeutic challenge. Given the rarity of the disease process and limited information on effective therapeutic modalities, rituximab should be viewed as a viable treatment option in the management of recalcitrant elephantiasic PTM.