A 35-year-old woman presents with a 2-week history of anterior neck pain, fever, and malaise. On examination, the thyroid is tender and enlarged. Thyroid function tests show elevated free T4 and suppressed TSH. Which is the most common cause of thyroiditis presenting with this acute inflammatory picture?

Explanation

## Subacute Granulomatous Thyroiditis — The Most Common Acute Thyroiditis ### Clinical Presentation Subacute granulomatous thyroiditis (also called de Quervain thyroiditis or viral thyroiditis) is the most common cause of acute thyroiditis with systemic symptoms. It typically presents with: - Severe anterior neck pain (often radiating to jaw or ear) - Fever and constitutional symptoms - Tender, enlarged thyroid gland - Triphasic thyroid dysfunction: hyperthyroid → euthyroid → hypothyroid phase ### Pathophysiology **Key Point:** Subacute thyroiditis is a granulomatous inflammation, likely viral in origin (often preceded by upper respiratory infection). The condition causes thyroid follicle destruction, releasing preformed thyroid hormones into circulation. ### Laboratory Features - Elevated free T4 and suppressed TSH (early phase) - **Very high ESR** (often >50 mm/hr) — hallmark finding - Low radioiodine uptake (distinguishes from Graves disease) - Elevated CRP - Thyroid peroxidase (TPO) antibodies typically negative or low-titer ### Histopathology - Granulomatous inflammation with multinucleate giant cells - Follicular destruction - Absence of fibrosis (unlike Riedel) ### Epidemiology **High-Yield:** Subacute thyroiditis accounts for ~5% of all thyroid disease and is the most common cause of acute thyroiditis. It is more common in women (female:male ratio 4:1) and typically occurs in middle-aged adults. ### Management - NSAIDs for pain and inflammation (first-line) - Beta-blockers for hyperthyroid symptoms - Corticosteroids in severe cases - Self-limited course; most recover within 6–12 months ### Differential from Other Thyroiditis Types | Feature | Subacute | Hashimoto | Riedel | Suppurative | |---------|----------|-----------|--------|-------------| | **Onset** | Acute (days–weeks) | Insidious (months) | Insidious | Acute (bacterial) | | **Pain** | Severe | Minimal | Severe (fibrosis) | Severe (infection) | | **ESR** | Very high (>50) | Normal/mildly elevated | Elevated | Very high | | **Antibodies** | Negative/low | High TPO/thyroglobulin | Negative | Negative | | **Histology** | Granulomas | Lymphocytic infiltrate | Fibrosis | Suppuration/abscess | | **Radioiodine uptake** | Low | Variable | Low | Low | **Clinical Pearl:** The combination of acute neck pain, fever, very high ESR, and low radioiodine uptake is pathognomonic for subacute thyroiditis. **Mnemonic:** **VAGUE** — Viral origin, Acute onset, Granulomatous, Ultrahigh ESR, Elevated free hormones (early phase).