Etiology of Incidental Asymptomatic Neutropenia and Prevalence of Benign Ethnic Neutropenia in Patients of Chinese Ethnicity.

Incidental asymptomatic neutropenia, where absolute neutrophil count (ANC) is less than the lower limit of normal, is a condition not associated with infection and does not require interventions. This condition overlaps with Benign Ethnic Neutropenia (BEN), which has been described in African Americans, Israel and Jordan ethnic groups. However, data on the identifiable causes on patients with asymptomatic neutropenia, or BEN in Chinese ethnic group is few. This study aims to evaluate the etiologies of neutropenia in asymptomatic patients of Chinese origin and to estimate the prevalence of benign ethnic neutropenia in this ethnic group.

Patients of Chinese origin, who were evaluated in Maimonides Hematology clinic between 1/2006 and 12/2008 for asymptomatic neutropenia, were included. Patients with current diagnosis of malignancy undergoing chemotherapy were excluded. Data were collected from chart review, including age, gender, medications, symptoms of infections, physical examination, complete blood counts with differentials, HIV, HBV status, vitamin B12 and folate levels and the duration of neutropenia.

Forty patients were identified, including 10 males and 30 females. The age ranges from 19 to 74 years old, with the median age of 42 years old. All patients were immigrants from Southeast region of China. All but one patient had persistent neutropenia. None had previous significant bacterial infections, while two patients reported associated viral symptoms and one of them showed transient neutropenia only. Three patients reported mouth sores, one of which was followed with serial blood tests which did not show further decrease from baseline. Majority of the patients demonstrated mild neutropenia. Twenty seven (68%) patients present showed grade 1 (ANC < lower limit of normal to 1500/mm²), 10 (25%) patients showed grade 2 (ANC 1000 to 1500/mm²) and 3 (7%) patients showed grade 3 (ANC 500 to 1000/mm²) neutropenia respectively. Probable causes of neutropenia were identified in 10 (25%) patients, including 2 patients with B12 deficiency, 4 patients with positive ANA while one confirmed for SLE and 2 patients with splenomegaly. The possible causes for other 2 patients were previous chemotherapy and current medications. Seventy five percent of the patients have no apparent causes, among them, 11 (27.5%) patients showed carrier status of HBV, and 2 patients have active HBV infection receiving treatment. No patients were found to have HIV infection.

Asymptomatic incidental neutropenia in Chinese ethnic group requires careful workup. Neutropenia can be the first presentation of rheumatologic diseases and B12 deficiency. There is a unique high rate of HBV carrier status and active infection in this ethnic group, its association with neutropenia is suspected and warrants further study. Benign ethnic neutropenia may be an entity in Chinese ethnic group, further prospective study targeting healthy subjects will yield more definitive information in Chinese ethnic group.

No relevant conflicts of interest to declare.