Case Presentation: Bartonella henselae classically presents in immunocompetent children as regional lymphadenopathy and fever following a cat bite or scratch. Atypical manifestations such as neuroretinitis and oculoglandular syndrome are well described, but sacral osteomyelitis is exceedingly rare. We report the case of a 4 year old male with fever, sacral pain and splenic lesions initially raising concern for malignancy but ultimately diagnosed with disseminated Bartonella infection with splenic lesions and sacral osteomyelitis.A previously healthy 4-year-old male presented with two weeks of fever, sacral pain, and decreased appetite following a fall. Initial evaluations for appendicitis and constipation were unrevealing, and persistent symptoms led to repeat emergency department visits and eventual admission. Laboratory studies showed an elevated ESR (73) and CRP (8.3), with a CBC notable only for thrombocytosis (489); the CMP was unremarkable. As the patient was well appearing without neurological deficits, empiric antibiotics were deferred pending further diagnostic evaluation. Given the history of a fall, MRI of the sacrum was obtained, which revealed ill-defined enhancing marrow infiltration of the S2 region and right iliac wing with periosteal extension into the neural foramen. The differential diagnosis included an oncologic etiology, osteomyelitis, Langerhans Cell Histiocytosis, and chronic recurrent multifocal osteomyelitis (CRMO). As part of oncologic evaluation, an abdominal ultrasound was obtained and showed mild hepatosplenomegaly with multiple hypoechoic splenic lesions. The constellation of marrow infiltration of the sacrum and hypoechoic splenic lesions raised significant concern for malignancy. Given this, bone marrow biopsy was performed which showed no evidence of a neoplastic process. CT-guided sacral biopsy demonstrated histiocytic proliferation with acute and chronic inflammation, with infectious studies pending. Upon further Pediatric Infectious Disease evaluation, Bartonella and TB testing were sent given the patient’s recent international travel and exposure to kittens. Bartonella henselae serologies returned positive and PCR from sacral tissue confirmed infection. At time of discharge, cultures remained negative and inflammatory markers down-trended. Treatment was started with Azithromycin.
Discussion: Bartonella osteomyelitis is a rare cause of osteomyelitis, but typically involves the vertebrae. Sacral involvement is rare with only a few case reports, and can resemble malignancy on imaging. Hypoechoic splenic lesions, while a well-documented manifestation of systemic Bartonella infection, can further complicate the picture by mimicking oncologic processes. Nondiagnostic bone marrow studies and a comprehensive exposure history helped narrow the differential in this case. Our patient completed a 4 week course of Azithromycin and had complete resolution of sacral pain and fevers with improvement of splenic appearance on abdominal ultrasound. There is no consensus on treatment duration in the pediatric literature.
Conclusions: Bartonella henselae can present as marrow infiltration and hepatosplenomegaly with hypoechoic lesions mimicking malignancy. This case highlights the importance of broadening the differential when initial oncologic work up is negative, especially with relevant exposure history.