“Are scratches safe?” Cat Scratch Disease & Osteomyelitis

MRI left forearm

~ By a Pediatrician and Infectious Disease Specialist in the US

I would like to present a “rare complication” of “not so rare disease.” The case also illustrates the importance of a complete medical history, including contact with animals.

A 12-year-old was recently admitted with swelling of the left proximal forearm and elbow joint for 5 days.  It was associated with soreness and restriction of movement of the same area.  Family also gave a history of diffuse left neck swelling associated with fatigue which has resolved without treatment approximately 6 weeks ago.  It had lasted for three or four days.  CT scan of the neck at that time showed reactive lymph nodes.  Basic lab work was unremarkable six weeks ago.  EBV titers and rapid strep were negative. The patient was sent home on Augmentin for incidental maxillary sinus disease noted on the CT scan.

MRI left forearm

Patient was apparently asymptomatic in the intervening period until five days before this admission for left elbow and forearm pain with painful restriction of movement. He did not report any redness or warmth over the area of the left elbow joint or the forearm. The patient is exposed to 2 cats at home, and mother reports that he and the cats are “attached at the hip.” The cats sleep with him in his bed. He also cleans the litter of the cats. The patient reports that the “cats are scratching him all the time.” At the time of admission he was nontoxic in appearance, and his vitals were stable.  Physical examination was positive for significant diffuse swelling, stiffness and tenderness over the elbow joint and extending over the proximal forearm. His neck examination was normal. On admission patient Hemoglobin and leukocyte levels were normal. C-reactive protein level was elevated, at 18.3 mg/liter. Tumor markers were normal. HIV serology was negative.  Acute antibody titers for Bartonella henselae IgG and IgM were both reactive at 1:512 and 1:80, respectively. An MRI of the left forearm was indicative of left proximal ulnar osteomyelitis and myositis (see attached image). It did show infiltrative edema and enhancement in the deep proximal forearm musculature. There was also a small elbow joint effusion. This prompted Bone Biopsy, arthrocentasis & I & D. Bone biopsy indicated a granulomatous tissue consistent with cat scratch disease (suppurative granulomas with central necrosis containing disintegrating neutrophils surrounded by palisading epithelioid cells and lymphocytes). The tissue was also positive for Bartonella by PCR. Initially patient was started on Vancomycin and Ceftriaxone  till the definitive diagnosis was available. Anaerobic, aerobic, fungal, and mycobacterial cultures of blood and osseous tissue obtained did not grow any organism.

MRI left forearm

A diagnosis of Left ulna osteomyelitis, left elbow joint synovitis and left proximal forearm myositis was made.  Our first differential diagnosis was Cat scratch disease or Bartonella henselae infection. The diagnosis was established by serology, histopathology, and PCR analysis of osseous tissue. The timeline was classical with the history of close and prolonged exposure to cats.  No active cat scratches were seen though few well-healed linear scars on forearms were seen. The patient did not have any ocular features or hepatosplenomegaly. However, the patient does have osteomyelitis which is seen with cat scratch fever. Osteomyelitis of cat scratch disease usually resolves without antibiotics but we did use Azithromycin. The patient’s history of left neck tumefaction (transient abnormal enlargement of a body part or area not due to cell proliferation) and fatigue, which had since resolved, goes with the self-limiting nature of the cat scratch disease which can sometimes be bimodal and recurrent.

MRI left forearm

The other differential diagnoses which were entertained and were ruled out included mycobacterial infection. This could be either an atypical or classical Mycobacterium tuberculosis infection of the bone; however, tuberculosis is rare in our geographical area. Chest x-ray and PPD testing were negative.  Bone sample was cultured and sent for PCR.  Both were negative for Mycobacterium. Classical bacterial osteomyelitis and Lyme disease were appropriately ruled out.  Bone biopsy was negative for malignancy.  Chronic recurrent autoimmune nonbacterial osteomyelitis in children was a distant possibility.  However, that condition is recurrent and multifocal.  Langerhans’ Histiocytosis was ruled out by HPE.

Literature Review:

Osteomyelitis is a rare complication of cat scratch disease (CSD). CSD, caused by B henselae, is a common zoonosis.  Cats and young kittens are the typical reservoir. CSD can result from a cat scratch or bite, as well as from a flea bite.  It can also occur after scratches from dogs, monkeys, and thorns. CSD is typically a self-limited regional lymphadenopathy. CSD may cause a wide variety of systemic manifestations, including, for example, Parinaud oculoglandular syndrome (conjunctivitis with ipsilateral preauricular lymphadenopathy), neuroretinitis, encephalitis, meningitis, seizures, hemiplegia, erythema nodosum, hepatosplenic involvement, endocarditis, glomerulonephritis, and pulmonary nodules. Musculoskeletal complications of CSD are uncommon. In patients with typical CSD, a 5-day course of azithromycin has been shown to improve clinical symptoms. Currently, there are no recommendations for the treatment of CSD-associated osteomyelitis. Only aminoglycosides have demonstrated in vitro bactericidal activity; however, different antibiotic regimens (including cephalosporins, penicillin, macrolides, rifampin, tetracyclines, cotrimoxazole, gentamicin, aminoglycosides, and vancomycin) have resulted in good recovery in all cases. Furthermore, patients who have received no antibiotic treatment have had complete recovery too. Prognosis of CSD-associated osteomyelitis is generally good, with no fatalities reported.


  1. Lamps LW, Scott MA. Cat-scratch disease: historic, clinical and pathologic perspectives. Am J Clin Pathol. 2004;121(suppl):S71-S80.
  2. Maman E, Bickels J, Ephros M, et al. Musculoskeletal manifestations of cat scratch disease. Clin Infect Dis. 2007;45:1535-1540.
  3. Hajjaji N, Hocqueloux L, Kerdraon R, Bret L. Bone infection in cat-scratch disease: a review of the literature. J Infect. 2007;54:417-421.
  4. Bass JW, Freitas BC, Freitas AD, et al. Prospective randomized double blind placebo-controlled eval-uation of azithromycin for treatment of cat-scratch disease. Pediatr Infect Dis J.


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