[A patient with relapsing-remitting multiple sclerosis who relapsed frequently and developed primary biliary cholangitis after pregnancy and discontinuation of fingolimod].

We present the case of a 37-year-old woman who was diagnosed as having relapsing-remitting multiple sclerosis (MS) when she was 25 years old. She remained relapse-free after she was started on treatment with oral fingolimod. However, at the age of 35, when she became pregnant, fingolimod was discontinued, and she began to suffer from frequent relapses. Following her delivery, she was started on treatment with dimethyl fumarate. Subsequently, with elevation of the serum levels of hepatobiliary enzymes and peripheral blood eosinophil count, possibly caused by dimethyl fumarate, her treatment was switched back to fingolimod. However, the elevation of the serum hepatobiliary enzyme levels and peripheral blood eosinophil count persisted. A serological test for autoantibodies revealed the diagnosis of primary biliary cholangitis (PBC). Pregnancy or discontinuation of fingolimod could have influenced the immune status of the patient and worsened the state of MS. There are some reports of autoimmune hepatic diseases, including PBC, being caused by disease modifying drug (DMD), like interferon-β or even steroid pulse therapy, although the underlying mechanisms remain unknown. This risk should be borne in mind when treating patients with MS, especially younger women, with DMD.