Fever of unknown origin and leukemoid reaction as initial presentation of adult-onset Still's disease.

Adult Still's Disease has been reported as cause of Fever of Unknown Origin. Leukocytosis has been described as a common haematological abnormality in Adult Still's Disease. In some rare cases, leukemoid reaction has been reported associated to Still's Disease. We report the case of Adult Still's Disease presenting as Fever of Unknown Origin and leukemoid reaction in a patient with Down Syndrome. The patient needed high dosage of corticosteroids to control the disease and haematological findings.