Primary myxoedema with idiopathic thrombocytopenia

Abstract

To the Editor: Graves' disease, Hashimoto's thyroiditis and primary hypothyroidism are considered chronic autoimmune thyroid disorders (1). All these three are relatively common, with primary hypothyroidism being even more prevalent than Graves' hyperthyroidism (1). Whereas very many cases of either Hashimoto's thyroiditis or particularly Graves' disease may co-exist with idiopathic thrombocytopenic purpura (ITP) (2, 3), ITP association with primary hypothyroidism has been limited to few cases and mostly with borderline subclinical hypothyroidism (3). The literature, in addition, lacks documented evidence of the concurrence of ITP and idiopathic myxoedema. This study describes the first case report of the clear association of ITP and idiopathic myxoedema. Besides, it presents ideas of why, in spite of having a higher prevalence than Grave's disease, primary hypothyroidism is still much less commonly associated with ITP. An 18-year-old woman presented with menorrhagia and facial puffiness. Her thyroid gland was not palpable and she had a nonpitting pretibial oedema. Her thyroid-stimulating hormone (TSH) levels were markedly elevated, whereas her thyroid hormone levels were very low. Antithyroglobulin and thyroid peroxidase antibodies were both negative. On sonography, her thyroid echogenicity was similar to that of her submandibular gland. In addition, there was no evidence of lymphocytic thyroiditis in thyroidal fine needle aspiration biopsy (FNAB) cytology. She was diagnosed as having idiopathic myxoedema and her symptoms and signs resolved with thyroid hormone replacement therapy. Shortly before, she had been found to be thrombocytopenic, with platelet counts of 70,000–80,000/mm3. Extensive investigations had failed to disclose a cause for her thrombocytopenia and she was under observation. Temporary discontinuation of thyroid hormone on several occasions resulted in a reappearance of symptoms and signs of hypothyroidism with elevated TSH and decreased T4 levels necessitating the resumption of hormone replacement therapy. At 21 years of age, while continuing her thyroid replacement therapy, she first experienced excessive menstrual bleedings and then tarry stools requiring hospital admission. Petechiae and ecchymoses had appeared on her lower extremities and there was a haemorrhagic bulla in her mouth. Her platelet count had fallen to 8000/mm3 (Figure 1, left panel). Levels of TSH and thyroid hormones remained normal. Extensive investigations disclosed no diseases, conditions or medicines to account for her low platelet count. She had had no transfusions or drug abuse. She did not drink alcohol and had no toxic substance exposure. She took no regular medication except thyroid hormone. Smear of bone marrow aspiration showed normocellular marrow with increased megakaryocytes (Figure 1, right panel). A peripheral blood smear confirming the decreased platelet count (left panel); smear of bone marrow aspirate showing normocellular marrow with increased megakaryocytes (right panel). Possible reasons for these seemingly marked differences in the rates of association of ITP with any of the three chronic autoimmune thyroid diseases can be the following. First is the fact that patients with goitrous Hashimoto's disease are often treated with thyroid hormone well before their disease even progresses to subclinical hypothyroidism. A subsequent ITP in such patients would still, most probably, be considered in association more with the initial Hashimoto's thyroiditis than with the consequent hypothyroidism masked by thyroid hormone therapy (1). Another reason could be related to differences in age-of-occurrence of these three thyroid diseases (1). Graves' hyperthyroidism is particularly common in the third and fourth decades of life when ITP also is most common. Hashimoto's thyroiditis occurs most frequently in middle age and is therefore in proximity to the life period when ITP has its usual occurrence. At the same time, primary hypothyroidism is mostly diagnosed after mid-fifties, the period of life deemed much less likely for ITP to occur. Several diagnostic procedures can now be used in combination in order to view chronic autoimmune thyroiditis and idiopathic (primary) myxoedema as separate entities (1, 4, 5). These are the measurements of antithyroid antibody levels (1, 4, 5), thyroidal FNAB cytology (4) and thyroidal ultrasonography (4, 5); on the basis of the same diagnostic modalities, the case presented in this study, a 21-year-old woman, is the first report of the concurrence of ITP and a documented idiopathic myxoedema. Then, this association could probably lend support to a still autoimmune nature of the latter.