A Case of Extremely Elevated Ferritin Levels in a Patient with Fever of Unknown Etiology

ABSTRACT

Fever of unknown etiology that occurs along with highly elevated serum ferritin concentrations (>500 ng/mL) is mostly observed in hematologic malignancies and rheumatic diseases such as systemic lupus erythematosus, temporal arteritis, and adult-onset Still's disease (AOSD), among which AOSD is a type of systemic inflammatory disorder with unknown pathophysiology and has very low incidence. AOSD presents with various nonspecific symptoms and signs such as high spiking fever, joint pain, skin rash, and increased leukocytes. Because AOSD is diagnosed after excluding the possibility of other conditions such as neoplasms, infections, and inflammations, diagnosis and treatment are generally delayed. Patients with AOSD often have high serum ferritin levels than those with other conditions, although the underlying mechanism for this is not clearly understood. In addition, decreased proportion of glycosylated ferritin are observed in most patients with AOSD. Therefore a combination of high serum ferritin and a decreased proportion of glycosylated ferritin seems to be important for the differential diagnosis of AOSD that thus may allow early diagnosis of AOSD. Here we report a case of AOSD diagnosed via extremely high serum ferritin levels and decreased glycosylated ferritin proportion.