Infectious sacroiliitis caused by Bartonella henselae in an immunocompetent adult: An unusual case

Cat scratch disease (CSD) is the most common manifestation in humans caused by Bartonella henselae (Bh).¹ In adults, there are atypical signs and symptoms with extranodal (e.g., musculoskeletal) involvement.^2–4 The following is the first case of an adult patient with sacroiliitis secondary to Bh infection, a site of infection not previously reported in the literature. A 57-year-old woman with a history of controlled hypertension. A housewife whose neighbour trains cats, she fell with a blow to her right hip, with no clinical or radiographic evidence of fracture. She followed a favourable course with a gradual decrease in local pain. Two weeks later, she presented a productive cough with mucopurulent expectoration and a sensation of fever which was not measured, in addition to pain in the right gluteus radiating towards the knee, associated with a mild functional impediment. She had no other symptoms. On admission, she was tachycardic, normotensive and afebrile with 4 l/min of oxygen via cannula for 91% saturation. Physical examination revealed diffuse rhonchi in both lung fields, tenderness in the right and left upper quadrant and pain on deep palpation of the right gluteus. Laboratory values: haemoglobin 15.8 g/dl, platelets 130,000 µl, leukocytes 10,510 µl (predominantly neutrophils), CRP 303 mg/l (normal value: <5), total bilirubin 5.89 mg/dl, direct bilirubin 1.94 mg/dl, GOT 84 U/l, GPT 82 U/l, GGT 133 U/l and AP 195 U/l. A chest X-ray showed right basal condensation. An abdominal ultrasound revealed a narrow bile duct and splenomegaly.

She was hospitalised with a diagnosis of right basal pneumonia and started on empirical treatment with ceftriaxone 2 g/day and clarithromycin 500 mg/every 12 h. After completing 10 days of antibiotic therapy, the patient followed a favourable course with respect to the respiratory tract, and her liver test results normalised. Her elevated liver tests results were interpreted to have reflected a context of sepsis. However, she showed persistent intermittent fever and elevated inflammatory parameters, with increasing pain and functional impediment of her right hip. The study was extended with HIV ELISA, blood cultures, urine culture, sputum culture with Kinyoun stain, smear microscopy and Koch culture. All were negative. Computed tomography of the abdomen and pelvis showed findings consistent with right sacroiliitis with focal bone resorption and splenomegaly, with no lumboaortic or iliac lymphadenopathy. Bone scintigraphy did not show other foci of hyperenhancement. In the absence of clinical indications of a non-infectious inflammatory aetiology, the patient was started on empirical treatment with piperacillin/tazobactam and vancomycin. She was evaluated for trauma, and joint aspiration and surgery were ruled out. After 24 days of treatment, the patient followed a course with less gluteal pain; she was afebrile, her CRP level had normalised and her ESR was 48 mm/h. It was decided to discharge her, with instructions to continue empirical antibiotic treatment at home with Co-Trimoxazole Forte, covering micro-organisms that typically infect the bone, and with close monitoring by an outpatient internal medicine team. Two weeks later, positive anti-Bh IgG was recovered with titres above 1:1,024. The patient's treatment was adjusted to doxycycline 100 mg/every 12 h. She completed treatment in 4 months, with an asymptomatic course.

It has been reported that up to 10% of patients with CSD have an atypical presentation such as neuroretinitis, encephalitis, erythema nodosum, hepatitis, pulmonary nodules or musculoskeletal involvement.^1–3 We reported the case of a patient in whom the only clinical sign of Bh infection was sacroiliitis. Few published studies in the literature report the frequency of musculoskeletal manifestations (MSMs). One of them analysed 913 subjects diagnosed with CSD between 1991 and 2002. 10.5% presented an MSM: 5.8% had myalgia and 5.5% had arthralgia/arthritis.² The most commonly affected joints were the knees (23%), wrists (20%), ankles (18%) and elbows (11%); no cases of sacroiliitis were reported.³ Among patients with joint disease, 42% presented severe compromise of weigh-bearing joints that limited walking, similar to that reported in our case.^2,3

Regarding risk factors, it has been reported that being over 20 years of age and being female are significantly associated with developing MSM.^2,3 Our patient presented both risk factors.

In atypical cases of CSD, the non-specificity of the signs and symptoms requires a high level of suspicion. Our case is a clear example, in which the bartonellosis study was proposed due to the patient's persistent fever. At present, the most widely used diagnostic method is serology, in which an anti-Bh IgG titre of >1:256 is highly suggestive of a current or recent infection.⁴

Lastly, we would like to mention that there are no pathognomonic radiological signs of osteoarticular compromise by Bh. In the literature, they are generally described as osteolytic lesions, similar to our case.⁵