From the symptom to the disease: asthenia

Asthenia is a common symptom that is shown to be a cause of medical consultation in teenagers, but is also in common in children and breastfed infants. Two clinical cases are presented, one of a 4-year-old girl and another of a 14-year-old teenager who, from the same asthenia symptom, two different diagnoses were arrived at in the Primary Care clinic: infectious Mononucleosis due to Epstein-Barr virus associated with pneumonia and acute renal failure. This article also deals with the anamnesis, physical examination, aetiological diagnosis, complementary examinations, and finally, for the paediatrician, the most common reasons for asthenia in children and adolescents.