In the Mayo Clinic study, 83 percent of JDM patients had cells from their mother. This compares to 23 percent of their unaffected siblings who had maternal cells, and 17 percent of healthy children who had maternal cells in their blood. The presence of this maternal (also called chimeric) cell is strongly associated with a particular genetic makeup of the mother. Children with JDM may suffer organ failure in the same way transplant patients often do. Because of this resemblance to a type of organ rejection disease, the Mayo Clinic team investigated the idea that non-self or chemeric cells may play a role in initiating JDM.

The Mayo Clinic researchers discovered two new aspects of chimeric cells. First, they remain in the offspring after birth and are related to the HLA genes, and second, chimeric cells are not merely present in the children ” but they are active, as shown by the attacks they mount against the child ™s body.

About the Disease JDMJDM causes inflammation of the blood vessels under the muscle and skin. This results in muscle damage, as well as in tissue changes of skin over the eyelids, finger joints and knuckles. Symptoms appear gradually and include: muscle pain and tenderness; difficulty swallowing, which results in weight loss; irritability; fatigue; fever; rash around the eyelids, finger joints, knuckles, elbows, ankles or knees.

Diagnosis may involve blood tests to detect muscle enzymes and markers of inflammation; an electromyography (EMG) to assess nerve or muscle damage; muscle biopsy for examination; X-rays; and MRI. Current treatments include medications to reduce inflammation and skin rashes; physical and occupational therapy to improve muscle function; and nutritional support.

[Reed, A.M., McNallan, K., Wettstein, P., Vehe, R., and Ober, C. (2004). Does HLA-dependent chimerism underlie the pathogenesis of juvenile dermatomyositis? J. Immunol. 172, 5041-5046.]