Intracellular folate concentrations in Down syndrome patients with arthritis

Purpose Patients with Down syndrome (DS) have an increased prevalence of arthritis compared to the general population, and often the arthritis is severe and debilitating. In light of the concern for folate deficiency in this patient population, and a clinically observed increased risk for methotrexate (MTX) toxicity, we investigated intracellular folate concentrations in DS patients on methotrexate therapy.