An 85-year-old female is referred to your practice for assessment of neutropenia. She is on 22 medications and does not remember the names. She denies any infections or systemic symptoms.
- What other investigations would you order?
- What are common medications associated with neutropenia?
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Diagnosis: idiosyncratic drug-induced neutropenia (IDIN)
Q1: What other investigations would you order?
B12 levels, infectious workup +/- autoimmune work-up or bone marrow biopsy
Q2: What are common medications associated with neutropenia?
See Box for IDIN drugs
IDIN Drugs (Anti-)
• Anti-thyroid (thionamides)
• Antibiotics (amoxicillin, cotrimoxazole)
• Antivirals (valganciclovir)
• Antipsychotic (clozapine)
• Sulfasalazine
Neutropenia can result from reduced bone marrow production, margination of neutrophils into tissues, or neutrophil destruction. Some populations (e.g. patients of sub-saharan African or Arab ancestry) have lower mean neutrophil counts compared to European and Asian populations. Severe neutropenia (< 0.5) is associated with an increased risk of bacterial and fungal infections. Patients should be counselled to monitor for signs of fever/infection and to seek medical attention if present.
When evaluating a patient with isolated neutropenia, it is important to assess other cell lines for abnormalities. In this case, the patient presents with an isolated neutropenia, which is in keeping with drug-induced or congenital cause. If additional cell lines were involved, further investigations such as bone marrow biopsy may be warranted to rule out a primary marrow disorder (e.g. MDS or aplastic anemia).
CBC Pearls
IDIN and congenital neutropenia often present as isolated neutropenia (other cell lines preserved)
If the patient had signs of infection, an infectious work-up (blood cultures, chest x-ray, etc) would be warranted. Finally, consideration for nutrition deficiencies (vitamin B12) and autoimmune disease should be considered based on the history and physical examination.
IDIN can be challenging to diagnose and there are limited reports on offending agents. However, some common classes of offending medications can be remembered by the prefix “anti-“ e.g. antibiotics, anti-thyroid, etc. (see Box).