Cat-scratch disease, a manifestation of bartonellosis, is a zoonotic bacterial infection caused by the Bartonella henselae microorganism. It is typically elicited by a scratch of a cat.
The disease has a varying clinical picture ranging between localized lymphadenitis and systemic infection. Due to the slow course, non-specific symptoms, and insidious onset, radiology often plays an important role in suggesting the diagnosis.
The injury leading to infection is typically a very superficial scratch, which often heals before the patient presents with the disease 1,2. Initial systemic symptoms are usually mild and non-specific (malaise, sore throat, aches, weight loss, headache, nausea, vomiting) 3.
Major forms of bartonellosis:
- the most common form (90%) of cat-scratch disease is a painful regional lymphadenopathy which first occurs adjacent to the entry point of the infection
- the lymph nodes of the upper extremity, axilla, head and neck are affected most commonly, which reflects that most cat scratches occur on the hand 1-3
- disseminated infection occurs in 5-10% of cases, manifesting as multiple granulomas (particularly in the liver and spleen); bone lesions may also develop in both the axial skeleton and extremities
- in 2-4% of patients neurologic complications also occur, ranging between encephalitis, transverse myelitis, polyneuritis, and neuroretinitis 1,2
- in patients with acquired immunodeficiency syndrome (AIDS), Bartonella henselae can cause bacillary angiomatosis
Bartonella henselae is facultative intracellular, Gram-negative bacterium which most commonly infects humans through a cat scratch or bite 1,2.
Bone lesions are typically ill-defined and lytic. The radiographic appearance is non-specific 1. Regional lymphadenitis results in diffuse soft tissue swelling 3.
Usually the initial imaging method of choice, ultrasound can depict both the regional lymphadenomegaly and lymphadenopathy, as well as liver and spleen granulomas, which are typically initially hypoechogenic, showing calcification in the late phase 1.
CT is useful for the assessment of systemic, disseminated disease. Abdominal granulomas are typically hypoattenuating on nonenhanced CT. Upon administration of intravenous contrast they can remain hypoattenuating, become isodense to the surrounding tissues, or demonstrate rim enhancement 1.
MRI can be used for further evaluation of the local and systemic form of the disease. Affected lymph nodes are typically hyperintense on T2 weighted sequences, demonstrate surrounding soft tissue edema, and enhance following the administration of intravenous contrast. MRI is particularly useful in the evaluation of the rare CNS sequelae (encephalitis, meningitis) 1,3.
Bone lesions show increased radiotracer uptake during bone scans, thereby mimicking malignancy 1.
Treatment and prognosis
The regional form of bartonellosis commonly resolves spontaneously within 3 months. Short-course antibiotic treatment is very effective if the correct diagnosis is made in time. Due to the aspecific symptoms and the diversity of systemic manifestations it can be however easily confused with other illnesses, such as soft tissue tumors 2,3.
- 1. K L Hopkins, S F Simoneaux, L E Patrick, J B Wyly, M J Dalton, J A Snitzer. Imaging manifestations of cat-scratch disease. (2013) AJR. American journal of roentgenology. 166 (2): 435-8. doi:10.2214/ajr.166.2.8553962 - Pubmed
- 2. Chen,Ying, Fu,Yan‑Biao, Xu,Xiu‑Fang, Pan,Yao, Lu,Chen‑Ying, Zhu,Xiu‑Liang, Li,Qing‑Hai, Yu,Ri‑Sheng. Lymphadenitis associated with cat‑scratch disease simulating a neoplasm: Imaging findings with histopathological associations. (2018) Oncology Letters. 15 (1): 195. doi:10.3892/ol.2017.7311 - Pubmed
- 3. P R Dong, L L Seeger, L Yao, C B Panosian, B L Johnson, Jr, J J Eckardt. Uncomplicated cat-scratch disease: findings at CT, MR imaging, and radiography. (1995) Radiology. 195 (3): 837-9. doi:10.1148/radiology.195.3.7754017 - Pubmed