Pathology · patient case question
Her oral ulceration is most likely a direct effect of which agent, and by what mechanism?
Patient case: Joints, immunosuppression and a sore mouth
demo: 58-year-old female
chief: Painful mouth ulcers that appeared over the last three weeks and are interfering with eating.
history: Seropositive rheumatoid arthritis for eleven years, currently in low disease activity. She was also treated for latent tuberculosis before starting her biologic.
meds: Methotrexate 20 mg weekly with folic acid. Adalimumab (Humira) every other week. She completed a nine-month course of isoniazid last year.
findings: Multiple shallow, painful ulcers on the buccal mucosa and lateral tongue with erythematous halos. No vesicles. Mild pallor of the conjunctivae.
Show answer and explanation
Correct answer: D. Methotrexate, through folate antagonism impairing epithelial turnover
- A. Folic acid is given precisely to reduce methotrexate mucosal and marrow toxicity. Deficiency, not supplementation, causes ulceration.
- B. Isoniazid can cause a lupus-like syndrome and peripheral neuropathy, but she completed that course a year ago, so it cannot explain ulcers appearing three weeks ago.
- C. TNF inhibitors increase infection risk and can provoke lupus-like and psoriasiform reactions, but they are not a common direct cause of aphthous-like ulceration in the way methotrexate is.
- D. Correct. Methotrexate inhibits dihydrofolate reductase, starving rapidly dividing cells of the thymidine they need. Oral and gastrointestinal mucosa turn over quickly, so stomatitis and ulceration are among the earliest and most common toxicities. Folic acid supplementation reduces but does not eliminate the risk.