A 28-year-old pregnant woman (12 weeks gestation) is diagnosed with Graves' hyperthyroidism. She is euthyroid on propylthiouracil (PTU). At 16 weeks gestation, she is switched to methimazole. At 18 weeks, she presents with nausea, vomiting, and fever. Lab shows WBC 900/μL with neutrophils 200/μL. What is the MOST likely diagnosis and immediate action?
- A Agranulocytosis from methimazole — immediately stop methimazole, start G-CSF, broad-spectrum antibiotics ✓
- B Drug-induced hepatitis from PTU — check LFTs and stop PTU
- C Graves' thyroid storm — start PTU, steroids, and beta-blocker
- D Hyperemesis gravidarum — IV fluids and antiemetics
Explanation
Agranulocytosis is a rare but life-threatening complication of thionamide drugs (methimazole > PTU), occurring in ~0.1–0.3% of patients, usually within the first 3 months of therapy. Presenting symptoms include fever, sore throat, and oropharyngeal ulcers. Absolute neutrophil count <500/μL confirms agranulocytosis. The drug must be IMMEDIATELY discontinued. Management includes hospitalisation, broad-spectrum IV antibiotics to cover gram-negative organisms, and G-CSF (granulocyte colony-stimulating factor) to hasten neutrophil recovery. Neither drug should be resumed; radioiodine or thyroidectomy (second trimester) should be planned.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.