Differential Diagnosis (DD) of Febrile Diseases
Establishing a diagnosis from several clinical presentations is a challenge in paediatrics that needs knowledge and experience to solve. This chapter provides clinicians with a guide to clinical and laboratory means to reach a diagnosis of the most common febrile diseases.
Infection is the most likely diagnosis in a child with fever, where the fever is usually of short duration and is associated with a focus in about three quarters of cases, and without a focus in the majority of the remaining cases.
Viral infections, affecting mainly the upper respiratory tract (URT), are the cause of fever in about 90–95% of febrile children. It is the physician’s primary role to identify the remaining 5–10% of children who have a bacterial infection and who may require antibiotic treatment. Nowadays, most cases of tonsillitis, otitis media and pneumonia, during the first years of life, are caused by a viral infection.
In the tropics, bacterial and parasitic infections are more common than in developed countries and are important causes of mortality of millions of children.
Pyrexia of unknown origin is considered when fever persists for more than 1 week, and its cause is unknown despite thorough investigation. In contrast to adults, PUO in children is mostly due to infection followed by collagen and vascular causes. The diagnosis of fever of non-infectious origin is considered after excluding an infection. This is done by history, physical examination and laboratory tests. Persistent and/or insidious fever of a low degree (<39.5 °C), the absence of chills and diurnal rhythm of fever are suggestive of non-infectious fever.
Other subjects discussed in this chapter include the differential diagnoses in pneumonia, abdominal pain, gastroenteritis, jaundice, coma, blanching rash, arthritis and seizures.