Neutropenia in Congenital and Adult Babesiosis

Anemia and thrombocytopenia are expected hematologic abnormalities in patients with acute babesiosis, whereas neutropenia (defined as an absolute neutrophil count of ≤1,800 neutrophils/μL for adults and <1,200 neutrophils/μL for infants) is not usually considered a feature of this infection. We studied the frequency with which neutropenia occurs in congenital and adult cases of babesiosis.

The frequency of neutropenia in cases of congenital babesiosis was determined based on a literature review and on the findings in an unreported case. The frequency of neutropenia in adult patients was assessed based on a review of the medical records of 51 patients who were diagnosed with babesiosis between 2010 and 2013 at two medical centers in the Northeastern United States.

Four (80%; 95% confidence interval [CI], 36%-98%) of five infants with congenital babesiosis whose neutrophil count was reported were neutropenic. Among 51 adult cases with babesiosis, 11 (22%; 95% CI, 12%-35%) were neutropenic on clinical presentation, and seven others developed neutropenia over the next 1 to 21 days. Thus, a total of 18 (35%; 95% CI, 24%-49%) of the adult patients with babesiosis had neutropenia.

Neutropenia appears to be a common finding in infants with congenital babesiosis and is also observed not infrequently in adults with this infection.