Plaque form of pretibial myxedema in hypothyroidism

Mala Dharmalingam¹ , G Seema² , B Khaitan³ , A Karak³ , AC Ammini³

¹ Department of Endocrinology, All India Institute of Medical Sciences, New Delhi, India
² Department of Dermatology, All India Institute of Medical Sciences, New Delhi, India
³ Department of Pathology, All India Institute of Medical Sciences, New Delhi, India

Correspondence Address:
Mala Dharmalingam
No 10 Yamunabai Road, Madhavanagar, Bangalore - 560001
India

Introduction

Pretibial myxedema (PTM) is an infiltrative dermopathy. It is a very rare clinical finding and when present it is usually seen in 5-10% of Graves thyrotoxicosis.[1],[2] However, it has also been described in autoimmune thyroid disease, like Hashimotos thyroiditis and idiopathic hypothyroidism.[3] The diffuse, non pitting variety is more commonly described. The other forms of plaque, nodule and tubular are rare. We present an uncommon form of PTM, the plaque form in a hypothyroid individual.

Case Report

A 27 - year - old man presenting with plaque lesions on the dorsum of the leg and foot for the past 3 years was seen in our OPD. Patient was apparently normal three years back when he developed raised lesions on the leg and foot. A year ago he resorted to indigenous medicine both systemic and local, following which there was worsening of the lesions with increasing size, and serous discharge. On further questioning, he admitted having cold intolerance, lethargy and weight gain for the past one year which worsened over the past two months. There was no family history of thyroid dysfunction or enlargement.

His height was 165 cms with a body weight of 100.5 kg and body mass index (BMI) of 36.73. The other physical examination was not contributory except that the deep tendon reflexes were delayed. The thyroid was not enlarged. Dermatological examination revealed well defined indurated plaques measuring 8 x 6 cms, having sloping margins, mildly erythematous with hyperpigmentation in the center, lobulated surface, with loss of hair on anterior aspect of left leg. Similar lesions measuring 2 x 3 cms and 2 x 2 cms were present on the right leg.

Patient was biochemically evaluated, the ft3 was 1.0 pg/ml (Normal - 1. 4-4.4) and fT4 was o.2ng/ dl (Normal - 0.8-2.0) with the TSH of 95.0 ulU/ml (Normal 0.2-5). The thyroid antibodies were positive, thyroid microsomal antibody (TMA) positive 1:1600 titre (N-Negative in this dilution) and anti thyroglobulin antibody (TGA) positive 1: 640 titre. (N-Negative in this dilution). The ultrasound of the thyroid showed a normal right lobe with a small left lobe. The CT of the orbit did not reveal any enlargement / infiltration of the ocular muscles. Ultrasonogram of the skin lesions showed the dermis and the epidermis to be thickened.

Histopathology of the skin lesion showed a dermal mucin accumulation which was compatible with pretibial myxedema.

Discussion

Pretibial myxedema is a poorly understood autoimmune process, usually occurring with Graves thyrotoxicosis.[1] Salvi et al have studied 76 patients with pretibial myxedema and found it to be present, 76.31% in Graves, 17.1% in Hashimotos thyroiditis, and 6.5% in idiopathic hypothyroidism.[4] It was 64% of the times associated with ophthalmopathy.[3]

Epidemiological studies have shown that 4% of the patients with clinically evident opthalmopathy have demopathy. In the above patient the pretibial lesions were present in a nongoitorous form of autoimmune thyroiditis. There was no associated orbiteropathy. The lesions are more common in the female in the sixth decade. The msot common form of presentation is the diffuse non pitting edema form. It can appear as a raised plaque lesion, sharply circumscribed tubular or nodular lesion. Very rarely they are elephantiastic, polypoid, or fungating.[5] The common sites include the pretibial region and the dorsum of the foot. The lesions present in the patient were of the plaque variety which is an uncommon manifestation.

In the study by Salvi et al,[4] it was histopathologically confirmed in all the patients though clinically suspected only in 28%. The histopathologic finding of mucin accumulation confirmed the diagnosis of pretibial myxedema. Ultrasound examination of the lesions showed a dermal thickening[4] which was also confirmed in this patient.

Pretibial myxedema presenting as a diffuse plaque form in a hypothyroid young male is very uncommon.

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