Ectopic Thyroid Gland Causing Dysphonia: Imaging and Molecular Studies

An 8.5-yr-old clinically euthyroid girl presented with a lingual mass, dysphonia, and occasional dysphagia. Screening for congenital hypothyroidism at 3 d had been positive [i.e. TSH, 37 mU/liter (normal, <15); total T4, 112 nm/liter (normal, 86–260)], but not the repeat test at 18 d [i.e. TSH, 12 mU/liter (<15); T4, 99 nm/liter (normal, 65–180)], so no diagnostic evaluation had been performed. The presence of a lingual mass was noted at around age 5 yr. Linear growth proceeded along the 95th percentile, and psychomotor development was normal. Family history was negative. On examination, a lingual mass was observed, and the thyroid was not palpable loco classico (Fig. 1A). On computed tomography scan, the mass was hyperdense and enhanced with contrast, and it measured 17 × 17 × 23 mm (Fig. 2A); there was no orthotopic thyroid. 123Iodine and 99mTc sodium pertechnetate scintigraphies confirmed the presence of an ectopic lingual thyroid (Fig. 2, B and C). Serum free T4 was 8.47 pmol/liter (normal, 8.3–20.3), TSH was 6.61 mU/liter (normal, 0.5–6.2), and thyroglobulin was 620.21 μg/liter (normal, 1.7–38.4). The volume of the mass and the dysphonia did not change under l-T4 75 μg/d by mouth (2.6 μg/kg · d), so the lingual thyroid was removed surgically. Pathology showed normal thyroid tissue (Fig. 1, B and C). Somatic mutations in exons and intron-exon junctions of genes involved in thyroid development (i.e. PAX8, NKX2.1, and FOXE1) were excluded by direct sequencing. This case is the first in which somatic mutations in these genes have been excluded in ectopic thyroid tissue. It further illustrates that ectopic thyroids have a normal follicular architecture and a normal capacity to trap and organify iodine and to produce thyroid hormones and thyroglobulin (1–3). This suggests that the hypothyroidism of subjects with thyroid ectopy is due to a smaller amount of tissue (absence of lateral lobes) with a limitation to TSH-induced growth, which is possibly a consequence of the migration defect, and is not due to defects in differentiation or in histological organization. A, Lingual thyroid visualized at the base of the tongue. B, Pathology showing normal thyroid tissue adjacent to the lingual mucosa (hematoxylin-phloxine-saffron staining; ×25 magnification). C, Normal follicular architecture (hematoxylin-phloxine-saffron staining; ×200 magnification). Ectopic thyroid gland shown by computed tomography scan (A), 123Iodine scintigraphy (B), and 99mTc sodium pertechnetate scintigraphy (C). We thank Dr. G. Van Vliet and Dr. Hervé Sartelet (Centre Hospitalier Universitaire Sainte-Justine, University of Montreal) for their support and collaboration. This work was supported by a scholarship of the Eugène Litta Foundation (to S.S.-V.); by a research junior 1 scholarship of the Fonds de Recherche en Santé du Québec, and a fellowship from the Canadian Child Health Clinician Scientist Program (to J.D.); and by the Belgian Fonds de la Recherche Scientifique Médicale and Fonds Erasme (to C.R. and G.V.). Disclosure Summary: All authors have nothing to disclose.

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