Differential Diagnosis for Cat Scratch Fever without Fever and Leukocytosis
Single Most Likely Diagnosis
- Cat Scratch Disease (CSD): This is the most likely diagnosis, as it typically presents with lymphadenopathy (enlargement of lymph nodes) after a cat scratch or bite, even in the absence of fever and leukocytosis. The disease is caused by Bartonella henselae and usually results in localized lymph node swelling.
Other Likely Diagnoses
- Toxoplasmosis: Caused by the parasite Toxoplasma gondii, this infection can lead to lymphadenopathy without systemic symptoms like fever. It's commonly associated with cat exposure, as cats are the definitive hosts of the parasite.
- Lymphogranuloma Venereum (LGV): Although typically associated with genital symptoms, LGV can cause lymphadenopathy without fever. It's caused by certain serovars of Chlamydia trachomatis and can be transmitted through contact with an infected cat's saliva or feces.
- Sporotrichosis: A fungal infection caused by Sporothrix schenckii, which can enter the body through cuts or scratches in the skin. It often presents with lymphocutaneous lesions and can cause lymphadenopathy.
Do Not Miss Diagnoses
- Lymphoma: Although less common, lymphoma (cancer of the lymphatic system) can present with isolated lymphadenopathy without systemic symptoms. It's crucial to consider this diagnosis to ensure timely and appropriate treatment.
- Tuberculosis (TB): TB can cause lymphadenopathy, and while it often presents with systemic symptoms like fever, it can be asymptomatic. Given its potential severity and the importance of early treatment, TB should not be missed.
- HIV: Human Immunodeficiency Virus infection can lead to persistent generalized lymphadenopathy. Early diagnosis of HIV is critical for managing the disease and preventing its progression to AIDS.
Rare Diagnoses
- Yersiniosis: Caused by Yersinia pestis or Yersinia pseudotuberculosis, these infections are rare but can present with lymphadenopathy. Yersinia pestis is the causative agent of plague, which can be transmitted through the bites of infected fleas that live on cats.
- Francisella tularensis (Tularemia): This bacterial infection can cause lymphadenopathy and is typically associated with contact with infected rabbits or other small mammals, but can also be transmitted by the bite of an infected cat or tick.
- Pasteurella multocida: While more commonly associated with animal bites, Pasteurella multocida can cause lymphadenitis (inflammation of the lymph nodes) following a cat scratch or bite.