To the Editor:
Pretibial myxedema (PTM) is bilateral, nonpitting, scaly thickening and induration of the skin that most commonly occurs on the anterior aspects of the legs and feet. Pretibial myxedema occurs in approximately 0.5% to 4.3% of patients with hyperthyroidism.1 Thyroid dermopathy often is thought of as the classic nonpitting PTM with skin induration and color change. However, rarer forms of PTM, including plaque, nodular, and elephantiasic, also are important to note.2
Elephantiasic PTM is extremely rare, occurring in less than 1% of patients with PTM.2 Elephantiasic PTM is characterized by the persistent swelling of 1 or both legs; thickening of the skin overlying the dorsum of the feet, ankles, and toes; and verrucous irregular plaques that often are fleshy and flattened. The clinical differential diagnosis of elephantiasic PTM includes elephantiasis nostra verrucosa, a late-stage complication of chronic lymphedema that can be related to a variety of infectious or noninfectious obstructive processes. Few effective therapeutic modalities exist in the treatment of elephantiasic PTM. We present a case of elephantiasic PTM.
A 59-year-old man presented to dermatology with leonine facies with pronounced glabellar creases and indentations of the earlobes. He had diffuse woody induration, hyperpigmentation, and nonpitting edema of the lower extremities as well as several flesh-colored exophytic nodules scattered throughout the anterior shins and dorsal feet (Figure 1). On the left posterior calf, there was a large, 3-cm, exophytic, firm, flesh-colored nodule. Examination of the hands revealed mild hyperpigmentation of the distal digits, clubbing of the distal phalanges, and cheiroarthropathy.
FIGURE 1. A, Diffuse woody induration, hyperpigmentation, and nonpitting edema on the right leg. B, Several flesh-colored papules were scattered throughout the anterior shins and dorsal aspects of the feet.
The patient was diagnosed with Graves disease after experiencing the classic symptoms of hyperthyroidism, including heat intolerance, tremor, palpitations, and anxiety. He received thyroid ablation and subsequently was supplemented with levothyroxine 75 mg daily. Twelve years later, he was diagnosed with Graves ophthalmopathy with ocular proptosis requiring multiple courses of retro-orbital irradiation and surgical procedures for decompression. Approximately 1 year later, he noted increased swelling, firmness, and darkening of the pretibial surfaces. Initially, he was referred to vascular surgery and underwent bilateral saphenous vein ablation. He also was referred to a lymphedema specialist, and workup revealed an unremarkable lymphatic system. Minimal improvement was noted following the saphenous vein ablation, and he subsequently was referred to dermatology for further workup.
At the current presentation, laboratory analysis revealed a low thyrotropin level (0.03 mIU/L [reference range, 0.4–4.2 mIU/L]), and free thyroxine was within reference range. Radiography of the chest was unremarkable; however, radiography of the hand demonstrated arthrosis of the left fifth proximal interphalangeal joint. Nuclear medicine lymphoscintigraphy and lower extremity ultrasonography were unremarkable. Punch biopsies were performed of the left lateral leg and posterior calf. Hematoxylin and eosin staining demonstrated marked mucin deposition extending to the deep dermis along with deep fibroplasia and was read as consistent with PTM. Colloidal iron highlighted prominent mucin within the dermis (Figure 2).
FIGURE 2. A, A biopsy of the left posterior calf showed marked mucin deposition in the superficial and deep dermis with deep fibroplasia (H&E). B, Colloidal iron staining highlighted the prominent mucin within the dermis. The notable deposition exceeds the typical amount of mucin seen in the setting of stasis, which pointed to a thyroid origin of disease.
The patient’s medical history, physical examination, laboratory analysis, imaging, and biopsies were considered, and a diagnosis of elephantiasic PTM was made. Minimal improvement was noted with initial therapeutic interventions including compression therapy and application of super high–potency topical corticosteroids. After further evaluation in our multidisciplinary rheumatology-dermatology clinic, the decision was made to initiate rituximab infusions.
Two months after 1 course of rituximab consisting of two 1000-mg infusions separated by 2 weeks, the patient showed substantial clinical improvement. There was striking improvement of the pretibial surfaces with resolution of the exophytic nodules and improvement of the induration (Figure 3). In addition, there was decreased induration of the glabella and earlobes and decreased fullness of the digital pulp on the hands. The patient also reported subjective improvements in mobility.
FIGURE 3. Following treatment with rituximab, there was striking improvement of the pretibial surfaces with nodules resolving; the induration substantially improved.