Chronic idiopathic neutrophilia: experience and recommendations

To distinguish chronic idiopathic neutrophilia (CIN) in a cost-effective manner from neutrophilia caused by important underlying illnesses.

This was a retrospective review of patients visiting a Veterans Affairs Medical Center over the last 10 years with a diagnosis of leukocytosis or myeloproliferative disorder. Of this group, fifty-seven patients from 1999 to 2008 were identified with CIN. Clinical and laboratory parameters were examined to identify CIN and establish its course. Eighty-one patients who presented from 2005 to 2010 with myeloproliferative disorders were also studied at time of diagnosis to determine any possible confusion with CIN.

The patients with CIN were followed for a mean of ≥ 7.3 years without progression to other serious disorders. Compared to non-CIN patients evaluated for neutrophilia, in multiple logistic regression analyses, smoking (P = .001) and increased BMI (P = .004) were significantly associated with CIN. No CIN patient developed a clinically apparent myeloproliferative disorder other than chronic myeloid leukemia (CML). Of the patients with myeloproliferative neoplasms reviewed at the time of their initial diagnosis, only CML occasionally presented with a picture consistent with CIN. For nonsmokers, the BMI of CIN patients was significantly higher than the average VA population (P < .001).

Cigarette smoking and obesity are confirmed as factors associated with CIN and may be causative. CIN is unlikely to develop into a clinically recognizable myeloproliferative neoplasm other than CML. Cost-effective guidelines for the diagnostic evaluation of neutrophilia in otherwise healthy patients are presented.