Causes of FUO in Infants and Children

Fever of unknown origin (FUO) is a relatively common pediatric complaint. The time of FUO generally ranges from 10 to 21 days. Generally the fever should be greater than 38.3 ˚c for at least 10 days with no evident source after initial outpatient or inpatient workup. A broad range of illnesses are known to cause FUO, including infectious, autoimmune and oncologic etiologies. Definitive diagnosis of FUO can be challenging, with many cases resolving spontaneously without a diagnosis. There is currently no standardized diagnostic approach for working up FUO. The general direction of the workup often depends on the patient's presentation, symptoms, and environmental exposures. It is generally accepted that a complete history and physical examination as well as basic laboratory tests, and empiric antibiotic therapy are initial steps in the workup of FUO. With no advanced resources available, radiographs such as chest X-rays and abdominal ultrasonography as well as simple tests e.g. ESR are commonly performed looking for infectious and malignant sources of FUO. If the diagnosis is still obscure laboratory tests for auto immune antibodies or specific infectious agents, are additional logical steps if the diagnosis remains in question.

Unlike adult studies, the categorical distribution of diagnosis of the causes of FUO in pediatrics has not changed in recent decades (Nield&Kamat , 2018) [1]. Additional studies are needed to improve the recognition of causes of prolonged fever in children.

So that FUO is not a single specific medical disorder but may be a potential manifestation of several diseases and disorders. The initial approach to FUO is suggested to be determination of the causes of prolonged fever in each of the body systems, as suggested by the presenting complaint. For instance in the respiratory system in developing countries tuberculosis (TB) must be searched for in the first place. Similarly Protein Energy Malnutrition (PEM), and vitamin D deficiency rickets must be also thought of as a cause of recurrent / chronic chest infection leading to FUO. In the gastrointestinal system persistant/ recurrent diarrhea must be searched for. In the developing countries, urinary tract infection, typhoid fever and viral hepatitis constitute other hidden causes of FUO. Collagen diseases, auto inflammatory diseases as well as immune deficiency diseases and auto immune disorders must be searched for as causes of FUO.