Infant with Fever and Splenomegaly—Time is Ticking

Introduction: We report on a case of babesiosis in an infant younger than 6 months who presented with fever and splenomegaly in late fall. Clinical Findings: This full-term, previously healthy infant was febrile at home and clinically well-appearing, though pale with splenomegaly on examination. Clinical Course: The patient presented with several days of irritability and pallor, following suspected viral illness with fever, and treated at home. Initial outpatient work-up revealed a normocytic anemia and splenomegaly was confirmed on abdominal ultrasound. They were admitted to the hospital for blood transfusion and comprehensive evaluation. Peripheral smear was normal and Babesia microti was detected by polymerase chain reaction. Parasite levels were less than 0.1%. They completed a 7-day course of atovaquone and azithromycin. They followed up with Pediatric Infectious Disease, which documented resolution of symptoms. Conclusions: Although a palpable spleen may be present in up to 30% of healthy infants, true splenomegaly (>1 to 2 cm below the costal margin) warrants a prompt further work-up. This work-up is particularly important if infants have other symptoms, such as fever, because fever may indicate a severe underlying illness. Although rare, babesiosis does occur in infants, and, thus, tick-borne illnesses should be considered.