Follistatin-like protein-1 as a biomarker for inflammatory disorders

A method of identifying a patient with systemic onset juvenile idiopathic arthritis who is at increased risk for developing macrophage activation syndrome comprising:

• (a) measuring the level of human FSTL-1 in a sample collected from the patient by an enzyme-linked immunosorbent assay;
• and
• (b) identifying the patient with systemic onset juvenile idiopathic arthritis as being at increased risk for developing macrophage activation syndrome if the level of human FSTL-1 in the sample of the patient is measured to be increased by about 40 percent or more relative to control levels.

A method of identifying a patient with Kawasaki disease who is at increased risk for developing macrophage activation syndrome comprising:

• a) measuring the level of human FSTL-1 in a sample collected from the patient by an enzyme-linked immunosorbent assay;
• and
• (b) identifying the patient with Kawasaki disease as being at increased risk for developing macrophage activation syndrome if the level of human FSTL-1 in the sample of the patient is measured to be increased by about 50 percent or more relative to control levels.