Background
Iodine-131 (I-131) is an essential treatment strategy for hyperthyroidism and thyroid cancer. Although the radioiodine therapy is generally safe, the patients may experience symptoms relating to early or late side effects. Precautionary measures can be taken to minimize or reduce these complications [1,2]. Iododerma is a rare complication of the I-131 therapy which is seen in the form of cutaneous lesions.
Iododerma is a dermatological lesion caused by oral, intravenous, or topical administration of iodides [3]. These skin lesions can be acneiform, erythematous, urticarial, hemorrhagic, vesiculobullous, pustular, carbuncular, petechial, or nodular. Commonly seen is acneiform lesion which is inflammatory follicular eruptions in the form of pustules [4].
Case Presentation
A 60-year-old female was referred to our department for radioiodine therapy. She was a diagnosed case of carcinoma (CA) thyroid. Thyroidectomy was done and the first dose of radioactive iodine (RAI) was given after 2 months of surgery. The patient was non-compliant and lost follow-up. Later the patient came after 8 years with bone and lung metastasis, the second dose of 7,400 Megabecquerel (MBq) was given and intravenous bisphosphonates were started as well. The third dose of 5,920 MBq was given 2 years after the second dose. Two weeks after the third dose, the patient developed numerous pustules and bullae on the trunk and limbs. Initially, the lesions were few in number but they rapidly spread all over the body.
On examination, there were hemorrhagic, palpable, large vegetative plaques. Rest of her physical examination was normal. Laboratory tests [complete blood counts and Immunoglobulin E (IgE)] were normal. History and clinical course supported the diagnosis of I-131 therapy-induced iododerma. The patient was treated with a topical cream (flumethasone and salicylic acid) and oral antihistamines. The patient’s lesions resolved gradually, leaving only post-inflammatory hyperpigmentation (Figure 1).
Discussion
Surgery followed by radioiodine therapy is an effective standard treatment in differentiated CA thyroid patients [5]. Radioiodine therapy is generally safe, but may be associated with complications, classified as acute (early) and late adverse effects [6]. Early complications include neck pain, swelling, tenderness, nausea/vomiting, thyroiditis, sialadenitis, xerostomia, and bone marrow (BM) suppression. Late complications include chronic sialadenitis, permanent BM suppression, pulmonary fibrosis, secondary malignancies, and impaired fertility [7]. Iododerma is a rare complication following the radioiodine therapy. Paul et al. [8] first in 2005 reported a case of iododerma after the radioiodine therapy for hyperthyroidism.
Iododerma is an uncommon drug reaction that occurs after systemic or oral intake of iodine. It is diagnosed on the basis of history, the clinical examination of characteristic cutaneous lesions, and the exclusion of other differentials as no laboratory or histopathology finding is pathognomonic [9,10].
Typically, the lesions begin as papules or pustules on the face or scalp and then extend to involve the neck, back, and extremities. It most commonly affects the areas having a higher concentration of sebaceous glands. However, the mucous membrane may be involved [11].The exact pathogenesis is unknown; however, hypersensitivity reaction to iodine, delayed iodine clearance, and leukocytes invasion are proposed possible mechanisms [3]. Clinical history and histopathology are considered to be the gold standard for diagnosis [11].
Case reports on iododerma with fatal outcome have been rarely reported. This may be due to the fact that the amount of iodine [as sodium iodide (20 μg of iodide per 100 mCi)] in RAI is many-fold smaller than that in a standard CT contrast dose (350 mg of iodide per ml) [12]. Iododerma after the radioiodine therapy is a self-limiting condition. However symptomatic treatment may be required for some types of lesions. Corticosteroids, antihistamines, or anti-inflammatory agents may be administered in a few cases [13].
Conclusion
Iododerma following the oral radioactive iodine administration is rarely reported. Clinicians need to know about possibilities of developing the skin lesions before administering iodine therapy. Knowledge of iododerma and its early identification is essential to avoid unnecessary treatment; thereby improving the overall management of the patient.