An otherwise healthy 8-year-old boy who lived in a rural area in Majorca was admitted due to an 11-day history of fever, abdominal pain, listlessness, anorexia, and 2kg weight loss. He also had headache and myalgias during the first few days of the illness. There were no enlarged lymph nodes, hepatosplenomegaly, or other positive physical examination findings. The initial laboratory tests showed 10,600leucocytes/mm3, with 50% neutrophils, and a C-reactive protein of 15.9mg/dL. Further laboratory evaluation on admission including serum alanine and aspartate aminotransferase levels, an ultrasound examination of the liver and the spleen, and a chest radiography revealed no abnormalities. On the basis of a working diagnosis of fever of unknown origin (FUO) a hospital diagnostic work-up was carried out over the following 2 weeks. The assessment consisted of the following studies: repeated measurements of full blood count (FBC), peripheral smear, erythrocyte sedimentation rate (ESR), and serum biochemistry, Mantoux skin test, blood and urine cultures, serology for Epstein-Barr virus (EBV), cytomegalovirus (CMV), adenovirus, influenza virus, enteroviruses, herpes simplex viruses, and for Rickettsia conorii, bone marrow aspirate to rule out malignancies, visceral leishmaniasis and miliary tuberculosis. The only positive finding was a gradual increase in the ESR value until a peak of 72mm/h on hospital day 14. In the meantime, he continued to be febrile with spikes up to 39.7°C late evening or at night, despite his good general condition and an unremarkable physical examination. However, the child's history of exposure to domestic cats found out on day 9 of hospitalization prompted us to order serology for Bartonella henselae. Serology for B. henselae, performed by indirect immunofluorescence assay, revealed a positive IgM with an IgG titre of 1:1024. The fever abated spontaneously 15 days after admission.
B. henselae infection should be included in the differential diagnosis of children with FUO, especially if there is a history of kitten or cat contact, as atypical cat-scratch disease (CSD) can present, irrespective of the immune status of the host, as FUO associated with hepatosplenomegaly due to hepatosplenic granulomatosis or, even more rarely, without hepatosplenic involvement.1
Fever of intermediate duration (FID) is a new syndrome, recently defined by adult infectious diseases specialists in our country as fever of 7–28 days which remains unexplained after the patient's history, physical examination, and basic laboratory and imaging screening. Since treatable infections with a good prognosis are by far the most commonly aetiology, the proposed diagnostic approach to this entity allows clinicians to avoid some expensive and uncomfortable procedures recommended for patients with classic FUO.2,3 Likewise, although FID has never been studied in children, the aetiology and prognosis of prolonged fever also varies greatly depending on whether the fever lasts for more or less than 4 weeks. For example, overall, infections can account for up to 50% of FUO in children in developed countries.4 The infections most commonly involved, regardless of local epidemiological particularities, are tuberculosis, EBV and CMV infection, other prolonged viral infections, CSD, osteomyelitis, and urinary tract infections.4,5 Most of these conditions can currently be diagnosed before fever reaches 4 weeks with the microbiological tests available. However, the likelihood of conditions with a worse prognosis such as connective tissue diseases, malignancies or inflammatory bowel disease dramatically increases when fever persists for more than 4 weeks without a clear origin.5–8In times of budget constraints in healthcare, the aetiology of FID is also worth studying in the paediatric population to optimise its management. We believe that a thorough clinical history, a meticulous physical examination, and a limited number of laboratory and imaging tests could be a rational initial approach to well-appearing and immunocompetent children. Additional investigations can be driven by new diagnostic clues discovered by revisiting the history and repeated physical examination.
