Clinical Pearls & Morning Reports

Posted by Carla Rothaus

Published April 14, 2021


What are some of the features of cat scratch disease? 

The approach to evaluating a patient with lymphadenopathy typically includes determining whether the lymphadenopathy is localized, involving only one region of the body, or whether it is generalized, affecting more than one region. Read the Case Records of the Massachusetts General Hospital here.

Clinical Pearls

Q: What are some causes of acute unilateral lymphadenitis?

A: Bacterial adenitis, which is usually caused by Staphylococcus aureus and Streptococcus pyogenes, is a common type of acute unilateral lymphadenitis. Less common causes of lymphadenitis include tularemia, nocardiosis, and sporotrichosis, all of which can cause regional lymphadenopathy distal to a site of inoculation. Typically, associated skin findings would be expected with tularemia, nocardiosis, and sporotrichosis; however, tularemia also has a glandular form without associated skin findings.

Q: Name two diseases associated with adenopathy and exposure to cats.

A: Toxoplasmosis and cat scratch disease are both associated with adenopathy and exposure to cats. Acute toxoplasmosis is manifested by a mononucleosis-like syndrome characterized by cervical lymphadenopathy or generalized, diffuse lymphadenopathy that is similar to that seen in patients with acute Epstein–Barr virus infection, acute cytomegalovirus infection, and primary HIV infection.

Morning Report Questions

Q: What are some of the features of cat scratch disease?

A:Bartonella henselae is the primary causative agent of cat scratch disease. Cats, particularly kittens, are the main reservoir of B. henselae; they transmit the bacteria through their saliva or through scratching (approximately 50% of cats are seropositive for B. henselae). Typically, a skin lesion (i.e., a papule, vesicle, or pustule) forms at the scratch site 3 to 10 days after inoculation; however, such a lesion is not always seen or properly identified. Approximately 2 weeks after inoculation, regional lymphadenopathy proximal to the inoculation site, a characteristic feature of cat scratch disease, develops. The most commonly involved sites of lymphadenopathy are the axillary, epitrochlear, cervical, supraclavicular, and submandibular regions. Generalized lymphadenopathy is rare, but up to a third of cases involve more than one anatomical site. Although lymphadenopathy associated with cat scratch disease usually resolves within 1 to 6 months without therapy, the current recommendation is treatment with a short course of azithromycin. 

Q: What are some of the sexually transmitted diseases commonly associated with inguinal lymphadenopathy?

A: The sexually transmitted infections that are commonly associated with inguinal lymphadenopathy are lymphogranuloma venereum (LGV), syphilis, and chancroid. LGV is a genital ulcer disease caused by the L1, L2, and L3 serovars of Chlamydia trachomatis. Historically, it has been most prevalent in the tropics and subtropics, but its prevalence has been increasing in high-income countries, primarily among men who have sex with men. The primary stage of infection is characterized by the presence of a genital ulcer at the site of inoculation that spontaneously heals within a few days. The secondary stage, occurring 2 to 6 weeks later, can be manifested by an enlarged, painful reactive inguinal node and is related to direct extension of the infection to the regional nodes. The secondary stage of syphilis is typically manifested by rash and generalized lymphadenopathy; regional lymphadenopathy would be atypical of syphilis.

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