Methotrexate-induced Hyperpigmentation in a Patient with Rheumatoid Arthritis

Abstract

Rheumatoid arthritis (RA) is a chronic progressive systemic and inflammatory disease affecting the lining of the synovial membranes, leading to inflammatory polyarthritis and extraarticular involvement in a symmetrical way. RA is known to be an autoimmune condition, which means that the body’s natural self-defense system gets confused and starts to attack the body’s healthy tissues. Treatment of RA is usually with disease-modifying antirheumatic drugs (DMARDs), but if left untreated, the risk of morbidity, mortality rate, and socioeconomic burdens will increase. Methotrexate (MTX) is one of the folic acid antagonists and one of the conventional synthetic DMARDs. It is the most common drug for the treatment of RA. MTX is a dihydrofolate reductase inhibitor that decreases purine metabolism, which affects cell division. MTX can also cause different types of cutaneous side effects, such as acral erythema, urticaria, ulcerations of the oral mucosa, burning sensation of the skin, multiform erythema, vasculitis, and hyperpigmentation to sun-exposed area. In this case report, we describe a 31-year-old woman who had RA and then developed MTX-induced hyperpigmentation.