Pathology · patient case question
What is the principal adverse effect that required monitoring during her isoniazid course?
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: A. Hepatitis
- A. Correct. Isoniazid hepatotoxicity ranges from asymptomatic transaminase elevation to fulminant hepatitis, and the risk rises with age and alcohol use. Liver enzymes are checked at baseline and periodically. Isoniazid also causes peripheral neuropathy by interfering with pyridoxine, which is why vitamin B6 is co-prescribed.
- B. Ototoxicity, both cochlear and vestibular, is again a streptomycin and aminoglycoside effect.
- C. Orange staining of urine, sweat and tears, which permanently discolours soft contact lenses, is the signature of rifampin.
- D. Nephrotoxicity is a feature of aminoglycosides such as streptomycin, not isoniazid.