infectious thyroiditis; suppurative thyroiditis; acute thyroiditis

Infectious thyroiditis, suppurative thyroiditis or acute thyroiditis is an uncommon form of thyroiditis caused by bacterial seeding of the thyroid, almost invariably from a blood-borne primary infection originating elsewhere. Etiology: 1) bacterial (68%) a) Staphylococcus b) Streptococcus c) Salmonella d) Enterobacter e) Mycobacterium tuberculosis 2) fungi (15%) a) Candida b) Aspergillus c) Mucor 3) parasitic (<1%) (Viral thyroiditis causes subacute granulomatous thyroiditis) Epidemiology: 1) most common in women 20-40 years of age 2) 50-60% of patients have pre-existing thyroid disease 3) 70% have concurrent upper respiratory tract infection Clinical manifestations: 1) abrupt onset of illness, may be preceded by upper respiratory tract infection (URI) a) anterior neck pain (100%) b) fever (92%) c) dysphagia (91%) 2) 4 phases of disease occurring over 4-6 months a) initial acute hyperthyroid phase (2-3 weeks) b) euthyroid phase c) hypothyroid phase (weeks to months) d) asymptomatic recovery phase Laboratory: 1) complete blood count (CBC) - increased WBC (70%) 2) fine-needle aspiration (FNA), Gram stain & culture 3) T4 generally normal 4) radioactive iodine uptake (RAIU) generally normal 5) thyroid auto-antibodies generally negative Radiology: ultrasound to exclude cervical abscess Differential diagnosis: 1) hemorrhage into adenoma or carcinoma 2) malignant neoplasm of thyroid a) fast growth with focal necrosis may mimic pyogenic infection b) hyperthyroidism may result from neoplasm by release of colloid-stored thyroxine 3) subacute granulomatous thyroiditis Management: 1) parenteral antibiotics 2) non-steroidal anti-inflammatory drugs (NSAIDs) 3) surgical drainage of abscess 4) rest & local heat 5) follow-up a) permanent sequelae rare b) hypothyroidism may occur if gland destruction is extensive c) recurrences suggest anatomic anomaly 1] persistent thyroglossal duct 2] fistula

References

Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 646-650