A 72- year old man presented to the dermatology clinic with a six-month history of indurated skin lesion involving both shins. The initial lesion started as asymptomatic, erythematous papules, which slowly coalesced and formed an infiltrative indurated plaque. Over the ensuing months the lesion enlarged to cover the entire lower two-third of the pretibial region, causing associated edema, itching and discomfort. There was no history of pretibial trauma or insect bite. He had no self or family history of thyroid illness and no current symptoms of thyrotoxicosis or thyroiditis.
He was known to have type 2 diabetes mellitus for the last 20 years and hypertension for 10 years. His medications included insulin, enalapril, atorvastatin and aspirin.
On physical examination, his blood pressure was 140/90 mmHg and body mass index 31 kg/meter2.
There was no palpable thyroid swelling, signs of ophthalmopathy or acropachy. He had central obesity with waist circumference of 115 cm.
Dermatological examination revealed an indurated translucent papules and plaque with erythematous and hyperpigmented background, non-pitting edema on the pretibial areas bilaterally with “peau d’orange” appearance [Fig. 1]. He had acanthosis nigricans with skin tags over the posterior neck, arm pit and elbow.
In our patient pretibial myxedema, necrobiosis lipoidica diabeticorum, stasis dermatitis and scleroderma were considered as possible causes of his skin lesion.
His free T4 was 15.4 pmol/L [reference range: [11–21], total T4 303 nmol/L [41–350], total T3 0.05 nmol/L [0.01–0.06], free T3 2.6 pmol/L [2–4], TSH 2.4 uU/ml [0.27–4.2]. His thyroid function tests were repeated three times in 1 month interval and were within normal reference range. Complete blood count, liver function tests, electrolytes were within normal reference range. His fasting blood sugar was 170 mg/dl and HbA1c [glycated hemoglobin] was 10%. Renal function tests showed creatinine 1.7 mg/dl [0.5–1.04], urea 47 mg/dl [14–45] and estimated glomerular filtration rate [eGFR] 38 ml/min/1.73m2 and he had proteinuria on urinalysis.
His Anti TSH receptor antibody [TRAB] was 0.52 IU/L [0–1.75], anti-thyroid peroxidase (TPO-Ab) was 10.8 IU/ml [2–34] and anti-thyroglobulin was 126 IU/ml [< 115]. Basal serum cortisol with adrenocorticotropic hormone [ACTH] were within normal range.
Neck ultrasonography was unremarkable. Doppler ultrasound of the lower limbs revealed normal arterial and venous study. Echocardiography showed mild left ventricular hypertrophy with grade 1 diastolic dysfunction.
Skin biopsy showed histopathologic features consistent of myxedema demonstrated by abundant mucin deposition in both papillary dermis and reticular dermis between thin fibrils of collagen with no associated inflammatory changes [Fig. 2].
The diagnosis of pretibial myxedema in a euthyroid state was confirmed and he was started on treatment with super potent topical corticosteroid under occlusion with significant clinical improvement [Fig. 3].