Can WBC Counts Increase in ANCA Vasculitis?
Yes, WBC counts can increase in ANCA vasculitis, but this is not a typical feature of the disease itself—elevated WBC counts more commonly indicate concurrent infection, treatment effects (particularly from glucocorticoids), or drug-induced vasculitis variants. In fact, certain drug-induced forms of ANCA vasculitis, specifically levamisole-induced AAV, characteristically present with neutropenia (low WBC counts) rather than leukocytosis 1.
Understanding WBC Patterns in ANCA Vasculitis
Drug-Induced ANCA Vasculitis and Neutropenia
- Levamisole-induced AAV specifically causes neutropenia along with retiform purpuric rash, high-titre MPO ANCA positivity, and dual MPO/PR3 ANCA positivity 1.
- Other drug-induced AAVs (from hydralazine, propylthiouracil, minocycline) are characterized by high-titre MPO ANCA positivity and dual ANCA positivity, but neutropenia is specifically associated with levamisole 1.
- Discontinuation of the offending agent is critical to control AAV and prevent relapses in drug-induced cases 1.
Treatment-Related WBC Changes
- 15-Deoxyspergualin, an alternative remission induction agent for refractory disease, is dosed specifically until WBC count reaches a nadir of 3000/ml, then held until WBC returns to >4000/ml before repeating the cycle 1.
- This demonstrates that treatment-induced leukopenia is an expected and monitored effect of certain AAV therapies 1.
- Glucocorticoids, a cornerstone of AAV treatment, commonly cause leukocytosis as a side effect, which can confound interpretation of WBC counts 1.
Clinical Monitoring Considerations
- WBC counts are not a primary disease activity marker in ANCA vasculitis—structured clinical assessment tools like the Birmingham Vasculitis Activity Score (BVAS) should guide treatment decisions 2.
- Essential monitoring parameters include urinalysis, inflammatory markers (ESR, CRP), renal function, and complete blood count, but CBC monitoring is primarily for detecting treatment-related cytopenias rather than disease activity 2.
Important Clinical Pitfalls
When encountering elevated WBC counts in a patient with ANCA vasculitis, prioritize ruling out infection before attributing it to disease activity, as serious infections are a major cause of morbidity and mortality in AAV patients receiving immunosuppression 1. The increased infection risk from plasma exchange (approximately 2.7-8.5% increase depending on baseline ESKD risk) and immunosuppressive therapy makes infection a critical differential 1.
Conversely, if you observe neutropenia in a patient with suspected ANCA vasculitis, specifically inquire about levamisole exposure (often from cocaine adulterated with levamisole) and look for the characteristic retiform purpuric rash 1.