Thyroid abscess of polymicrobial origin in a child

Acute suppurative thyroiditis (AST) and thyroid abscess are infectious processes in the thyroid gland that are extremely rare, accounting for 0.7%–1% of all thyroid disorders.¹ This low prevalence is due to the thyroid gland's intrinsic resistance to bacterial invasion, as a result of both its chemical and its anatomical characteristics.² In most cases, the infection's portal of entry is unknown, but colonisation of a distal region appears to be the most common cause.^3–6 Initial clinical signs are usually non-specific and difficult to detect, with painful inflammation developing in the anterior neck area as the condition progresses. This is a potentially serious condition.¹

Ultrasound is the first-line imaging technique.⁷ Treatment is based on intravenous broad-spectrum antibiotics aimed at covering germs in the patient's oropharyngeal flora. Fine-needle aspiration biopsy or surgical drainage must be performed if the clinical course demands it.⁸ With early diagnosis and treatment, the disease usually has a good prognosis. We report a case of acute suppurative thyroiditis complicated by a thyroid abscess.

A previously healthy 3-year-old boy had a fever up to 39.5 °C and odynophagia for the past 3 days. He presented with firm, painful swelling of the anterior neck slightly to the left with local erythema (Fig. 1A). Blood testing revealed leukocytosis (18 × 10⁹/l) with neutrophils 74.3% and lymphocytes 15.6%, C-reactive protein (CRP) 11 mg/dl and erythrocyte sedimentation rate (ESR) 38 mm/h. His thyroid hormone levels and antithyroid antibody levels were normal. An ultrasound of the neck showed enlargement of the thyroid gland at the expense of the left thyroid lobe, with a heterogeneous echostructure and an uneven hypoechoic area consistent with an in trathyroid abscess measuring 12 mm × 10 mm. Given the clinical picture consistent with a thyroid abscess, parenteral antibiotic therapy was administered with amoxycillin/clavulanic acid. After 48 h had elapsed since the start of treatment, the patient's fever disappeared and his laboratory test results improved; however, the swollen area on his neck increased in size. A follow-up ultrasound showed that the collection had enlarged up to 38 × 26 mm (Fig. 1B). Given the patient's poor clinical course, percutaneous abscess drainage was performed, yielding 30 mL of purulent material. In the days that followed, the patient made good progress with the swelling of his neck and his inflammatory signs gradually disappearing. Microbiological testing isolated Streptococcus con stellatus and Eikenella corrodens which were sensitive to the antibiotic therapy administered. Blood culture was negative. Following 10 days of intravenous antibiotic therapy, the patient was discharged to complete his treatment with oral amoxicillin/clavulanic acid for 11 days. Subsequent clinical monitoring was normal and magnetic resonance imaging (MRI) was performed which ruled out anatomical malformations.

Figure 1.

A) Cervical tumour in the hospitalised patient. B) Collection of heterogeneous echogenicity consistent with a left thyroid abscess measuring 38 mm × 26 mm.

Thyroid abscess is a very rare clinical condition that can occur in the context of acute suppurative thyroiditis, a disease that is unusual in itself.⁹ It can occur at any age, but it is rare in childhood.¹⁰ Its clinical presentation is characterised by inflammation and an increase in sensitivity in the anterior region of the neck, accompanied by fever and pharyngeal pain. As the initial signs are subtle, diagnosis is late in most cases.⁹ The left thyroid gland is more commonly affected, since the cause is usually a pyriform sinus fistula and thyroid function is usually normally, as in the case reported.⁷ The initial test of choice is an ultrasound of the thyroid gland. To rule out predisposing anatomical defects, and when retrosternal spread is suspected, a computed tomography (CT) scan, MRI or an oesophagogram is performed. Our case was exceptional because it involved a previously healthy boy with no associated anatomical abnormalities. Ultrasound-guided fine-needle aspiration biopsy is a simple procedure that enables diagnostic confirmation and yields a sample for microbiological testing.^4,6 The most commonly found micro-organisms are polymicrobial flora in the oral cavity, due to its anatomical cause. They are often Gram-positive bacteria such as Staphylococcus aureus and Streptococcus pneumoniae. More rarely, Gram-negative pathogens (Escherichia coli, Haemophilus influenzae, Klebsiella, Salmonella), Mycobacterium tuberculosis or fungi may be isolated.⁴ Therapeutic management includes empirical parenteral antibiotic therapy with broad-spectrum antibiotics.¹⁰ Surgery is indicated if there is any airway compromise or, in a second stage, if a pyriform sinus fistula is found.

Thyroid abscess is therefore very rare and requires strong clinical suspicion and early therapeutic management. Although the clinical course in most cases is benign, it should be considered a medical emergency due to the serious associated complications.