Cat scratch disease

Additional clinical information: Six-year-old boy with swollen lymph glands under right-side of jaw. Concern for peritonsillar abscess.


Findings

CT shows a heterogeneously enhancing, right submandibular level I lymph node with several additional smaller, scattered enhancing subjacent lymph nodes. There is overlying infiltration of the subcutaneous fat consistent with cellulitis.

Differential Diagnosis:
- Lymphoma
- Sarcoid
- Cat scratch disease
- TB/histoplasmosis
- Mononucleosis
- Metastatic disease
- Other bacterial infectious processes


Diagnosis: Cat scratch disease


Further clinical probing subsequently revealed recent, unmonitored contact with a cat.


Discussion

Self-limiting infectious disease characterized by painful regional lymphadenopathy following the scratch of a cat (typically a kitten).
Bartonella henselae, (gram-negative bacillus) - determined to be nearly exclusively responsible for CSD.

Epidemiology:
- 22,000 cases of CSD diagnosed annually in US (1993 data).
- 70-90% of CSD cases occur in the fall and early winter months. (presumed to be due to a midsummer rise in kitten births accompanied by increased flea infestation).
- M:F 3:2
- < 21 years of age (80% of cases)

Clinical:
- >90% of patients with the disease report recent contact with a cat, usually a kitten.
- Incubation period of 3-12 days is followed by the development of one or more cutaneous papules or pustules at the inoculation site.
- Primary lesion lasts for 1-3 weeks then recedes as regional lymphadenopathy appears, generally immediately proximal to the inoculation site.
- Regional lymphadenopathy, (approx. 90%) - most notable manifestation (usually prompts medical evaluation).
- Lymphadenopathy primarily involves axillary >cervical > inguinal regions.
- Lymph nodes are often painful and spontaneously suppurate in 25-30% of cases.
- Constitutional symptoms (usually mild); include malaise, low-grade fever, anorexia, nausea, fatigue, or headache.
- Erythematous, tender papules or pustules at inoculation site.
- Tender unilateral lymphadenopathy (>90%); 50% have involvement of a single node, 30% have involvement of nodes in multiple sites, and 20% with involvement of several nodes in the same region.
- Routine laboratory tests are usually unremarkable and unlikely to aid in diagnosis. Mild leukocytosis and elevated ESR are common but nonspecific.
- Indirect fluorescent antibody (IFA) for Bartonella (84-88% sensitive and 94-96% specific), and rising immunoglobulin G (IgG) titers (titers above 1:64 supportive) provide laboratory confirmation of diagnosis. PCR from lymph node biopsy provides even more sensitive detection of disease.
- Self-limiting disease with excellent prognosis, even in patients with profound manifestations - usually resolves spontaneously over 2-5 months with rare permanent sequelae. However, immunocompromised patients may experience a dramatic and potentially life-threatening course of disease.
- Management primarily symptomatic. Antibiotics not indicated in most cases, but may be considered for severe or systemic disease.

Radiographic Overview of Diagnosis:
- Non-specific unilateral regional lymphadenopathy at/proximal to the site of inoculation.