White Blood Cell Count in Lyme Disease

Expected Laboratory Findings in Lyme Disease

Routine laboratory parameters, including complete blood counts, are generally unremarkable in patients with erythema migrans and early Lyme disease, according to the Infectious Diseases Society of America 1
Unlike many bacterial infections, Lyme disease does not typically trigger leukocytosis, which helps distinguish it from other acute bacterial processes, as recommended by the Centers for Disease Control and Prevention 2

If a patient with suspected or confirmed Lyme disease presents with leukopenia, thrombocytopenia, or persistent high-grade fever (>48 hours despite appropriate antibiotics), strongly consider coinfection with Anaplasma phagocytophilum or Babesia microti, as suggested by the Infectious Diseases Society of America 1

The absence of leukocytosis is actually characteristic of Lyme disease and should not delay diagnosis when clinical features (erythema migrans, appropriate exposure history) are present, according to the Infectious Diseases Society of America 1 and the American Academy of Pediatrics 3
In patients with more severe initial symptoms than typically seen with Lyme disease alone, obtain a complete blood count with differential to assess for cytopenias that would suggest coinfection, as recommended by the Infectious Diseases Society of America 1

Do not exclude Lyme disease based on a normal WBC count, as this is the expected finding and supports rather than refutes the diagnosis, according to the Centers for Disease Control and Prevention 2
Do not assume all tick-borne illnesses present similarly, while Lyme disease has normal WBC counts, Rocky Mountain spotted fever may show normal or slightly elevated counts with bandemia, and anaplasmosis characteristically causes leukopenia, as noted by the Centers for Disease Control and Prevention 4

The American College of Physicians and the Infectious Diseases Society of America recommend considering Lyme disease in patients with erythema migrans, fever, headache, fatigue, and musculoskeletal pain 5, 6
The Centers for Disease Control and Prevention suggests that cardiac involvement occurs in approximately 4-10% of patients, typically presenting as atrioventricular heart block or myopericarditis, although this fact is from a less preferred source 7

The American Academy of Neurology and the American College of Rheumatology state that neurological manifestations include meningitis, cranial neuropathy (particularly facial nerve palsy), and radiculopathy 5, 8
The American College of Rheumatology recommends that joint involvement typically presents as monoarthritis or oligoarthritis, most commonly affecting the knee 9

The Infectious Diseases Society of America recommends considering coinfection with Anaplasma phagocytophilum or Babesia microti in patients with high-grade fever persisting >48 hours despite appropriate antibiotic therapy, unexplained leukopenia, thrombocytopenia, or anemia 9
The Centers for Disease Control and Prevention states that laboratory abnormalities in anaplasmosis include thrombocytopenia, leukopenia, elevated hepatic transaminases, and mild anemia, but not hyperammonemia 10
The Centers for Disease Control and Prevention reports that coinfection with A. phagocytophilum has been reported in <10% of patients with Lyme disease 10