COMMENTS
FINDINGS:
This subacute infection is usually self-limited. A red papule can be found at the site of a cat bite, lick, or scratch in 50%-90% of cases. Lymphadenitis develops. Some patients have prolonged high fever and lesions of the bone, liver, and spleen. Neurological complications occur in some patients. Fleas are known to transmit the pathogen from cats to cats, but not from cats to humans. [CCDM, p. 95-6] Several cases transmitted by ticks have been described. [Cecil, p. 1969] In addition to regional lymphadenopathy, some patients have fever. Atypical presentations include conjunctivitis in 6% of patients and neurological complications (meningoencephalitis, myelitis, and neuritis) in 2% of patients. Granulomas of the spleen and liver have been reported. [Merck Manual, p. 1578] Other presenting symptoms compiled from several case series are fatigue (20-45%), splenomegaly (8-12%), and headache (13%). Erythema nodosum and parotitis are possible complications. [ID, p. 1213, 1502] 85-90% of cases are typical: papule, blister, or nodule at inoculation site with painful regional lymphadenopathy (usually axillary or epitrochlear) >1-3 weeks after cat contact (scratched, bitten, or licked). 50% of patients have low-grade fever, malaise, and anorexia. Findings in atypical cases include eye involvement, neurological manifestations, and osteomyelitis. The disease (typical or atypical) resolves spontaneously without treatment after weeks or months in immunocompetent patients. [Harrisons, p. 489]
SYNDROMES:
There are 3 main syndromes of cat-scratch disease: typical CSD (88%), Parinaud's oculoglandular syndrome (6%), and atypical CSD (6%). Patients with typical CSD have regional lymphadenopathy, and 1/3 of these patients have involvement at more than one site. Patients with typical CSD also have fever for several days (30% to 60%), fatigue (25%), and headache or sore throat (10%). The primary lesion is a papule, pustule, or blister that may resemble an insect bite. Lymph nodes suppurate in about one sixth of patients. About 10-15% of patients present with a systemic illness consisting of headache, weight loss, and hepatosplenomegaly. Atypical syndromes include hepatitis/splenitis, pneumonitis, osteitis, and neurologic syndromes (encephalopathy and neuroretinitis). Encephalopathy usually follows in cases with lymphadenopathy, and symptoms may include persistent headache, combativeness, restlessness, seizures, nuchal rigidity, cranial nerve palsies, ataxia, and coma. Fever may be present or absent. Encephalopathy is usually self-limited over several weeks to a year. Bartonella henselae is an important cause of neuroretinitis that usually resolves in 2-3 months. Other complications are arthritis, atypical pneumonia, hilar adenopathy, and thrombocytopenia. [PPID, p. 1320-1, 2824-36]
REFERENCES FOR CASES/YEAR
1. (US) About 10 cases per 100,000 with about 10% of cases hospitalized; [Harrison ID, p. 580] Calculated to 30,000 cases using a population of 300 million;
2. (Global) 20 X US cases/yr;