Juvenile rheumatoid arthritis (JRA), also known as juvenile idiopathic arthritis (JIA), is a rare autoimmune joint disorder of children. The concrete causes for the prevalence of the above pathological state are still unknown. In other words, it is an arthritis affecting mainly children and adolescents. Clinically, it has 3 different clinical subtypes. JRA patients are often noticed with some confirmed symptoms including coagulopathy, disseminated intravascular coagulation (DIC) with hepatosplenomegaly, fall in erythrocyte sedimentation rate and higher levels of liver enzymes leading to a life-threatening outcome. The above complications of JRA are recognized as a macrophage activation syndrome (MAS), which is similar to hemophagocytic lymphohistiocytosis (HLH). Pathogenesis of JRA manly involves deregulation of immunological processes with excessive and persistent activation of antigen presenting cells and T-lymphocytes. Further, abnormalities in the functioning of NK cells are often observed in JIA cases. Also, 40% of patients with these abnormalities are habitually associated with perforin gene mutations. Today, MAS remains a clinical and diagnostic challenge.
The diagnosis of MAS is mainly based on clinical grounds. However, laboratory evidence of macrophages in the bone marrow performing phagocytosis of variable hematopoietic cells also help in diagnosis. For confirmation of MAS, there must be present either of two clinical or laboratory criteria. Further, laboratory criteria often appear late and are unable to diagnose the complication right at the beginning stage. Important laboratory findings in macrophage activation syndrome associated with JIA include hypertriglyceridemia, anemia, low erythrocyte sedimentation rate, elevated alanine aminotransferase level, higher than normal bilirubin levels, presence of fibrin degradation products, high lactate dehydrogenase level, low sodium, low albumin, and hyperferritinemia.
MAS is a confirmed life threatening complication of patients with JIA. Further, an early diagnosis and treatment of MAS could be a life-saving mode for this syndrome.