Question
You are seeing in follow-up a 46-year-old man who, 6 months ago, presented to the hospital acutely with hemoptysis, diffuse nodular pulmonary infiltrates, and glomerulonephritis. Workup revealed a positive serologic study for antibodies against cytoplasmic ANCA, and he was eventually diagnosed with granulomatosis with polyangiitis. Treatment was initiated with high-dose glucocorticoids and daily cyclophosphamide with excellent clinical response. You are ready today to have the patient transition from induction therapy with cyclophosphamide to maintenance therapy with azathioprine. What blood test should you check before starting azathioprine?
| A. |
ANCA titers
|
| B. |
Cryoglobulins
|
| C. |
CYP3A4 genotyping
|
| D. |
Thiopurine methyltransferase enzyme activity
|
Show Answer
[ads id=”53026″]
|
Correct Answer � D
Explanation
|
|
Ans. D
Treatment of granulomatosis with polyangiitis (Wegener’s) is currently viewed as having two phases: induction, where the active disease is put into remission, followed by maintenance.
Induction
cyclophosphamide combined with glucocorticoids
rituximab with glucocorticoids.
Remission maintenance
Methotrexate
Azathioprine
mycophenolate mofetil
Rituximab
Before initiation of azathioprine, thiopurine methyltransferase (TPMT), an enzyme involved in the metabolism of azathioprine, should be assayed because inadequate levels may result in severe cytopenia.
The antineutrophil cytoplasmic antibody (ANCA) titer can be misleading and should not be used to assess disease activity.Many patients who achieve remission continue to have elevated titers for years.
A rise in ANCA by itself is not a harbinger of immediate disease relapse and should not lead to reinstitution or an increase in immunosuppressive therapy.
Like this:
Like Loading...
