How is cat scratch disease diagnosed?
Your doctor is likely to suspect cat scratch disease from what you tell them and what they find when they examine you or your child. It's really important that you tell your doctor if you have a cat or a kitten, especially if they have recently scratched you or your child.
If your doctor suspects cat scratch disease, you will also need to have blood tests done to confirm the diagnosis. The blood tests will look for signs of inflammation in your body and for signs that your body is trying to get rid of B. henselae, the germ (bacteria) that causes cat scratch disease.
What other tests will I need?
If the only symptoms you have are a swollen gland (or glands) and a history or being scratched by a kitten or a cat and you have had the typical spots of cat scratch disease, you may not need any other tests other than the blood tests described above.
If you have other symptoms or if you have no recollection of being in contact with a cat or a kitten, you might need other tests. There are lots of other illnesses that have very similar symptoms to cat scratch disease, particularly cancer. It is therefore extremely important to get the correct diagnosis.
Other tests you might need could include:
- Lymph node biopsy - a small amount of tissue is removed from a gland (lymph node). It is then looked at under a microscope to make sure there aren't any cancer cells in it and it is also tested for germs. See separate leaflet called Biopsy for more information.
- Computerised tomography (CT) scan.
- Ultrasound scan.
- Magnetic resonance imaging (MRI) scan.
- Lumbar puncture.
- Electroencephalogram (EEG).
What are the possible complications of cat scratch disease?
Complications can occur if the infection gets into the eye or if it spreads to other parts of the body. Some of the complications include:
- Parinaud's oculoglandular syndrome - occurs when the germ gets into the eye and spreads to the gland (lymph node) in front of the ear.
- Neuroretinitis - occurs when the nerve that takes messages to and from the eye to the brain (the optic nerve) is damaged by the infection.
- Osteomyelitis - when the infection spreads to the bone. This is rare.
- Pseudo-malignancy - occurs when the symptoms and changes in the body make the infection look like there is a cancer present.
Some complications can be potentially life-threatening:
- Bacillary angiomatosis - is a rare complication in which blood vessels grow out of control in the skin and in organs inside the body. It mostly affects people who have AIDS or HIV.
- Hepatitis and splenitis (bacillary peliosis) - occurs when the germ infects the liver and the spleen.
- Infective endocarditis - can occur if infection spreads to the heart.
- Encephalitis and/or meningitis - inflammation of the brain (encephalitis) and/or the covering of the brain (meningitis) - is rare.
Did you find this information useful?
- Klotz SA, Ianas V, Elliott SP; Cat-scratch Disease. Am Fam Physician. 2011 Jan 15 83(2):152-5.
- Nelson CA, Saha S, Mead PS; Cat-Scratch Disease in the United States, 2005-2013. Emerg Infect Dis. 2016 Oct 22(10):1741-6. doi: 10.3201/eid2210.160115.
- Mazur-Melewska K, Mania A, Kemnitz P, et al; Cat-scratch disease: a wide spectrum of clinical pictures. Postepy Dermatol Alergol. 2015 Jun 32(3):216-20. doi: 10.5114/pdia.2014.44014. Epub 2015 Jun 15.
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