Infectious Diseases Case
A 15-year-old girl is evaluated in the emergency department (ED) for abdominal pain and fevers.
The fevers started about 3 weeks ago and have not resolved despite intermittent treatment with acetaminophen and ibuprofen. The girl has had some right upper quadrant pain for the last several days and had a small bump on her right arm a few weeks ago that has since resolved. She cannot remember any other symptoms. Because of no improvement in symptoms her family brought her in to be evaluated. On exam you note her to be febrile to 38.5°C (101.3°F) with a heart rate of 110 beats per minute, but she is non–toxic appearing. She has a somewhat tender right axillary lymph node that feels like it is approximately 3 cm in diameter. She has some tenderness in the right upper quadrant and the liver edge is palpable about 2 cm below the right costal margin. Her lab results are remarkable for a mildly elevated white blood cell count of 13,000 with neutrophil predominance and normal liver function tests. A computed tomography (CT) scan with contrast is ordered and shows a normal appendix and gallbladder but some mild hepatomegaly with multiple scattered small abscesses.
You explore the history further and are most likely to find that:
A. She recently went to rural Mexico.
B. She has a kitten at home.
C. She had Staphylococcus aureus bacteremia a few months ago that was treated with IV antibiotics.
D. She drinks unpasteurized milk.
E. None of the above.
The correct answer is B.
This patient has cat-scratch disease caused by Bartonella henselae. Cats, especially kittens, are known to carry the bacteria in their blood. Infection usually occurs after being scratched, but often patients cannot remember a specific scratch occurring. Typically a couple of weeks after the scratch, a red papule forms near the area of inoculation. The lesion then resolves and lymphadenopathy occurs somewhere along the chain of lymph nodes that drain the skin where the lesion occurred. Because scratches often occur on the arm, axillary and epitrochlear lymphadenopathy is common. Fever, though not always present, can develop and last for weeks. The lymph nodes may suppurate and drain or may require surgical drainage to improve pain. The disease often resolves spontaneously (may take months), though antibiotics may help symptoms to improve.
In some cases, more systemic involvement may occur, and liver and splenic lesions often are seen on CT scan or ultrasound. These lesions typically are small and scattered in the liver or spleen. They can calcify after disease resolution. The CNS and eye (neuroretinitis) may be involved as well.
Infectious organisms can reach the liver by several mechanisms such as bacteremia, contiguous spread of intra-abdominal infection, or traumatic inoculation. Organisms such as S. aureus are common owing to their propensity to cause bacteremia leading to their deposition in the liver. Gram-negative enteric organisms are common as well, due to spread from intra-abdominal infection such as appendicitis or cholangitis. Rarer causes include Brucella, which should be suspected if the patient has been exposed to livestock or unpasteurized dairy products. Travel to undeveloped countries should prompt inclusion of amebic abscess, such as Entamoeba histolytica, on the differential diagnosis. In these situations the abscess is often solitary, but a few smaller or larger abscesses may be present. Multiple small abscesses would be more likely in the setting of Bartonella infection.