Cat scratch disease presenting as fever of unknown origin is a unique clinical syndrome

BACKGROUND: Fever of unknown origin (FUO) is a rare manifestation of cat scratch disease (CSD). Data regarding CSD associated FUO (CSD-FUO), particularly in adults, are limited. We aimed to study disease manifestations and long-term clinical outcome. METHODS: A national CSD surveillance study is conducted in Israel since 1991. Data are obtained using questionnaires, review of medical records and telephone interviews. FUO was defined as fever of >14 days without an identifiable cause. CSD-FUO patients were identified in the 2004-17 CSD national registry. Follow-up included outpatient clinic visits and telephone/e-mail surveys. RESULTS: The study included 66 CSD-FUO patients. Median age was 35.5 (range 3-88) years. Median fever duration was 4 weeks (range 2-9). Relapsing fever pattern was reported in 52%, weight loss in 57% and night sweats in 48% of patients. Involvement of >1 organs occurred in 59% of patients; hepatosplenic space-occupying lesions (35%); abdominal/mediastinal lymphadenopathy (20%), ocular disease (18%) and multifocal osteomyelitis (6%) being the most common. Malignancy, particularly lymphoma was the initial radiological interpretation in 21% of patients; 32% underwent invasive diagnostic procedures. Of the 59 patients available for follow-up (median duration 31 weeks, range 4-445), 95% had complete recovery of symptoms; 3 patients remained with ocular sequelae. CONCLUSION: This is the first attempt to characterize CSD-FUO as a unique syndrome which may be severe and debilitating and often mimics malignancy. Relapsing fever is a common clinical phenotype. Multi-organ involvement is common. Recovery was complete in all patients except in those with ocular disease.