IgG4-Related Disease of the Thyroid Gland Requiring Emergent Total Thyroidectomy: A Case Report

Abstract

IgG4-related disease of the thyroid gland is a recently recognized subtype of thyroiditis, often with rapid progression requiring surgical treatment. It is considered as a spectrum of disease varying from early IgG4-related Hashimoto's thyroiditis (HT) pattern to late fibrosing HT or Riedel's thyroiditis patterns. Here, we report a 47-year-old Malay woman presenting with progressively painless neck swelling over 3 years and subclinical hypothyroidism. Computed tomography (CT) scan revealed diffuse thyroid enlargement (up to 13 cm) with retrosternal extension and without regional lymphadenopathy. Fine needle aspiration of the thyroid showed a limited number of follicular epithelial cell groups with widespread Hurthle cell change and scanty background colloid, but no evidence of lymphocytosis. The cytologic features fell into the category of 'atypia of undetermined significance'. Subsequently, the patient developed hypercapnic respiratory failure secondary to extrinsic upper airway compression by the thyroid mass and underwent emergent total thyroidectomy. Histology of the thyroid showed diffuse dense lymphoplasmacytic infiltrate and fibrosis. Follicular cells exhibited reactive nuclear features and some Hurthle cell change. IgG4+ plasma cells were over 40/high power field while overall IgG4/IgG ratio was above 50%. The overall features suggest the diagnosis of IgG4-related disease of the thyroid gland in the form of IgG4-related HT. Post-surgery, the patient was found to have markedly elevated serum IgG4 concentration but PET/CT did not show significant increased fludeoxyglucose uptake in other areas. Her recovery was complicated by a ventilator-associated pneumonia with empyema, limiting early use of corticosteroids for treatment of IgG4-related disease.

Keywords: Emergent total thyroidectomy; Hashimoto’s thyroiditis; IgG4-related disease; Thyroid.

Fig. 1

Computed tomography scan showed homogenous and diffuse thyroid enlargement measuring 8.4 × 13.0 × 12.7 cm with retrosternal extension. It displaced the surrounding structures and compressed the trachea (a coronal plane, b transverse plane)

Fig. 2

FNA cytology of the thyroid showed an adequate but low yield of follicular epithelial cells, which were mostly obscured by blood clot (a, original magnification ×200). They were arranged in acini, solid groups and papillaroid clusters (b, ×400). There was widespread Hurthle cell change (c, ×400), without lymphocytosis. Admixed stromal spindle cells were noted (d, ×600)

Fig. 3

Histology of the thyroid showed a multi-lobulated appearance with separating fibrous septae (a, original magnification ×2.5). Focal storiform fibrosis (b, ×50), diffuse dense lymphoplasmacytic infiltrate (c, ×100) with Hurthle cell change of follicular cells (d, ×400) were demonstrated. Focal vessels showed perivascular plasmacytic infiltrate (e, ×200). IgG4+ plasma cells were over 40/high power field and an overall IgG4/IgG ratio was above 50% (f, ×400: IgG in red, IgG4 in brown)