Usually a self-limited illness, cat-scratch disease (CSD) has two general clinical presentations. Typical CSD, the more common, is characterized by subacute regional lymphadenopathy; atypical CSD is the collective designation for numerous extranodal manifestations involving various organs. B. henselae is the principal etiologic agent of CSD. Rare cases have been associated with Afipia felis and other Bartonella species.
CSD occurs worldwide, favoring warm and humid climates. In temperate climates, incidence peaks during fall and winter; in the tropics, disease occurs year-round. Adults are affected nearly as frequently as children. Intrafamilial clustering is rare, and person-to-person transmission does not occur. Apparently healthy cats constitute the major reservoir of B. henselae, and cat fleas (Ctenocephalides felis) may be responsible for cat-to-cat transmission. CSD usually follows contact with cats (especially kittens), but other animals (e.g., dogs) have been implicated as possible reservoirs in rare instances. In the United States, the estimated disease incidence is ~10 cases per 100,000 population. About 10% of patients are hospitalized.
Inoculation of B. henselae, possibly via contaminated flea feces, usually results from a cat scratch or bite. Infection of mucous membranes or conjunctivae via droplets or licking may occur as well. With lymphatic drainage to one or more regional lymph nodes in immunocompetent hosts, a TH1 response can result in necrotizing granulomatous lymphadenitis. Dendritic cells, along with their associated chemokines, play a role in the host inflammatory response and granuloma formation.
CLINICAL MANIFESTATIONS AND PROGNOSIS
Of patients with CSD, 85–90% have typical disease. The primary lesion, a small (0.3- to 1-cm) painless erythematous papule or pustule, develops at the inoculation site (usually the site of a scratch or a bite) within days to 2 weeks in about one-third to two-thirds of patients (Fig. 69–1A, B). Lymphadenopathy develops 1–3 weeks or longer after cat contact. The affected lymph node(s) are enlarged and usually painful, sometimes have overlying erythema, and suppurate in 10–15% of cases (Fig. 69–1C, D, and E). Axillary/epitrochlear nodes are most commonly involved; next in frequency are head/neck nodes and then inguinal/femoral nodes. Approximately 50% of patients have fever, malaise, and anorexia. A smaller proportion experience weight loss and night sweats mimicking the presentation of lymphoma. Fever is usually low-grade but infrequently rises to ≥39°C. Resolution is slow, requiring weeks (for fever, pain, and accompanying signs and symptoms) to months (for node shrinkage).
Manifestations of cat-scratch disease. A. Primary inoculation lesion. Axillary and epitrochlear lymphadenitis appeared 2 weeks later. B. Primary inoculation lesion. Submental lymphadenitis appeared 10 days later. C. Axillary lymphadenopathy of 2 weeks’ duration. The overlying skin appears normal. D. Cervical lymphadenopathy of 6 weeks’ duration. The overlying skin is red. Thick, odorless pus (12 mL) was aspirated. E. Preauricular lymphadenopathy. F. Left-eye neuroretinitis. Note papilledema and stellate macular exudates (“macular star”).
Atypical CSD occurs in 10–15% of patients as extranodal or complicated disease in the absence or presence of lymphadenopathy. Atypical disease includes Parinaud’s oculoglandular syndrome (granulomatous conjunctivitis with ipsilateral preauricular lymphadenitis; Fig. 197–1E), granulomatous hepatitis/splenitis, neuroretinitis (often presenting as unilateral deterioration of vision; Fig. 69–1F), and other ophthalmologic manifestations. In addition, neurologic involvement (encephalopathy, seizures, myelitis, radiculitis, cerebellitis, facial and other cranial or peripheral palsies), fever of unknown origin, debilitating myalgia, arthritis or arthralgia (affecting mostly women >20 years old), osteomyelitis (including multifocal disease), tendinitis, neuralgia, and dermatologic manifestations (including erythema nodosum [see Fig. 14-40], sometimes accompanying arthropathy) occur. Other manifestations and syndromes (pneumonitis, pleural effusion, idiopathic thrombocytopenic purpura, Henoch-Schönlein purpura, erythema multiforme [see Fig. 14-25], hypercalcemia, glomerulonephritis, myocarditis) have also been associated with CSD. In elderly patients (>60 years old), lymphadenopathy is more often absent but encephalitis and fever of unknown origin are more common than in younger patients. In immunocompetent individuals, CSD—whether typical or atypical—usually resolves without treatment and without sequelae. Lifelong immunity is the rule.
Routine laboratory tests usually yield normal or nonspecific results. Histopathology initially shows lymphoid hyperplasia and later demonstrates stellate granulomata with necrosis, coalescing microabscesses, and occasional multinucleated giant cells—findings that, although nonspecific, may narrow the differential diagnosis. Serologic testing (immunofluorescence or enzyme immunoassay) is the most commonly used laboratory diagnostic approach, with variable sensitivity and specificity. Seroconversion may take a few weeks. Other tests are of low sensitivity (culture, Warthin-Starry silver staining), of low specificity (cytology, histopathology), or of limited availability in routine diagnostic laboratories (polymerase chain reaction [PCR], immunohistochemistry). PCR of lymph node tissue, pus, or the primary inoculation lesion is highly sensitive and specific and is particularly useful for definitive and rapid diagnosis in seronegative patients.
APPROACH TO THE PATIENT: Cat-Scratch Disease
A history of cat contact, a primary inoculation lesion, and regional lymphadenopathy are highly suggestive of CSD. A characteristic clinical course and corroborative laboratory tests make the diagnosis very likely. Conversely, when acute- and convalescent-phase sera are negative (as is the case in 10–20% of CSD patients), when spontaneous regression of lymph node size does not occur, and particularly when constitutional symptoms persist, malignancy must be ruled out. Pyogenic lymphadenitis, mycobacterial infection, brucellosis, syphilis, tularemia, plague, toxoplasmosis, sporotrichosis, and histoplasmosis should also be considered. In clinically suspected CSD in a seronegative individual, fine-needle aspiration may be adequate and PCR can confirm the diagnosis. When data are less supportive of CSD, lymph node biopsy rather than fine-needle aspiration is preferred. In seronegative CSD patients with lymphadenopathy and severe complications (e.g., encephalitis or neuroretinitis), early biopsy is important to establish a specific diagnosis.
TREATMENT Cat-Scratch Disease
(Table 69-2) Treatment regimens are based on only minimal data. Suppurative nodes should be drained by large-bore needle aspiration and not by incision and drainage in order to avoid chronic draining tracts. Immunocompromised patients must always be treated with systemic antimicrobials.
TABLE 69-2ANTIMICROBIAL THERAPY FOR DISEASE CAUSED BY BARTONELLA SPECIES IN ADULTS ||Download (.pdf) TABLE 69-2 ANTIMICROBIAL THERAPY FOR DISEASE CAUSED BY BARTONELLA SPECIES IN ADULTS
|DISEASE ||ANTIMICROBIAL THERAPY |
|Typical cat-scratch disease ||Not routinely indicated; for patients with extensive lymphadenopathy, consider azithromycin (500 mg PO on day 1, then 250 mg PO qd for 4 days) |
|Cat-scratch disease retinitis ||Doxycycline (100 mg PO bid) plus rifampin (300 mg PO bid) for 4–6 weeks |
|Other atypical cat-scratch disease manifestationsa ||As per retinitis; treatment duration should be individualized |
|Trench fever or chronic bacteremia with B. quintana ||Gentamicin (3 mg/kg IV qd for 14 days) plus doxycycline (200 mg PO qd or 100 mg PO bid for 6 weeks) |
|Suspected Bartonella endocarditis ||Gentamicinb (1 mg/kg IV q8h for ≥14 days) plus doxycycline (100 mg PO/IV bid for 6 weeksc) plus ceftriaxone (2 g IV qd for 6 weeks) |
|Confirmed Bartonella endocarditis ||As for suspected Bartonella endocarditis minus ceftriaxone |
|Bacillary angiomatosis || |
Erythromycind (500 mg PO qid for 3 months)
Doxycycline (100 mg PO bid for 3 months)
|Bacillary peliosis || |
Erythromycind (500 mg PO qid for 4 months)
Doxycycline (100 mg PO bid for 4 months)
|Carrión’s disease || |
| Oroya fever || |
Chloramphenicol (500 mg PO/IV qid for 14 days) plus another antibiotic (β-lactam preferred)
Ciprofloxacin (500 mg PO bid for 10 days)
| Verruga peruana || |
Rifampin (10 mg/kg PO qd, to a maximum of 600 mg, for 14 days)
Streptomycin (15–20 mg/kg IM qd for 10 days)
Avoiding cats (especially kittens) and instituting flea control are options for immunocompromised patients and for patients with valvular heart disease.