To the Editor: Pretibial myxedema (PTM) is a cutaneous manifestation of Graves disease that is often refractory to treatment even with control of underlying thyroid disease. We read with great interest the case series by Hoesly et al1 describing PTM successfully treated with hyaluronidase. Here we report a case of recalcitrant pretibial myxedema that improved significantly with intralesional hyaluronidase and triamcinolone.
Our patient is a 43-year-old man who had Graves disease diagnosed after presenting with thyrotoxicosis with hypercalcemic thyrotoxic periodic paralysis necessitating thyroidectomy because of disease severity. Two years after diagnosis, he presented to the dermatology department with an enlarging firm plaque on his right shin (Fig 1) refractory to compression therapy and topical corticosteroids. Also notable on examination was nail clubbing, acropachy, and proptosis with exophthalmos. Incisional biopsy found pools of mucin throughout the reticular dermis consistent with PTM. A mixture of intralesional hyaluronidase (Hylenex, Halozyme Therapeutics, San Diego, CA human recombinant hyaluronidase, 150 U/mL) and triamcinolone were injected into the plaque on the right leg during 5 consecutive office visits at 4-week intervals. For treatment, 1 mL of hyaluronidase (150 U) was mixed with 1 mL of 40 mg/mL triamcinolone at a 1:1 ratio and delivered in 0.05- to 0.1-mL aliquots spaced approximately 1 cm apart. This treatment regimen resulted in a roughly 90% reduction in volume of the plaque with most residual volume at the inferior aspect (Fig 2). Of note, the patient was also taking pentoxifylline, 400 mg 3 times a day, and reported intermittent use of compression stockings during the treatment period. The goal of treatment is a 100% reduction in volume of the plaque with the above regimen and continued use of pentoxifylline and compression therapy.
Fig 1.
Pretibial myxedema. Baseline (24 cm long × 17 cm wide × 2 cm deep).
Fig 2.
Pretibial myxedema. After 5 treatments (20.7 cm long × 13 cm wide × 0.3 cm deep).
Although the precise pathogenesis of PTM is unknown, it is theorized that circulating autoantibodies bind to TSH-Rs on fibroblasts, stimulating T cells to secrete cytokines that promote production of glycosaminoglycans, namely hyaluronic acid and chondroitin sulfate, resulting in excess mucin deposition within the dermis and subcutaneous tissue.2 PTM classically presents as bilateral, asymmetric, firm, nonpitting, painless nodules and plaques that favor the anterior shins. Conventional therapy includes topical or intralesional corticosteroids and pressure therapy as first line, with oral pentoxifylline as second-line therapy. Intralesional triamcinolone alone has been shown to decrease size and improve appearance of lesions of PTM.3 In the above case, we propose a synergistic effect when used with hyaluronidase. Hyaluronidase is readily available commercially to enhance the dispersion and absorption of subcutaneous drugs and to correct complications related to hyaluronic acid soft tissue augmentation. Treatments are generally well tolerated, with transient burning pain, erythema, and pruritus at the injection site.1,4,5
Footnotes
Funding sources: None.
Conflicts of interest: None disclosed.
References
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