Progressive multifocal leukoencephalopathy in a 27-year-old lady with systemic lupus erythematosus - rheumatoid arthritis overlap syndrome.

Progressive multifocal leukoencephalopathy (PML) is a rare viral demyelinating disease of central nervous system. Immunosuppression is a significant risk factor for the disease. Previously, PML developed more commonly in patients of hematological malignancy and acquired immune deficiency syndrome (AIDS). In the era of biological disease modifying anti-rheumatic drugs, PML is more frequently reported in patients of autoimmune diseases. However, for its rarity and unspecific clinical presentations, accurate diagnosis and immediate immune restoration might be difficult in clinical practice, and the outcome might thus be miserable. Herein we present a 27-year-old lady of systemic lupus erythematosus (SLE) - rheumatoid arthritis overlap syndrome with suspected involvement of central nervous system. Neuropsychiatric SLE was suspected first. However, after intensive immunosuppressive treatment, the condition kept deteriorating. An alternative diagnosis was thus considered. PML was suspected for her immunosuppressive status and suggestive radiological findings, and the diagnosis was confirmed by a polymerase chain reaction of JC virus from cerebrospinal fluid. After restoring the immune status by decreasing the dose of immunosuppressants, the condition of the patient improved significantly. We report this case to raise the importance of clinical alertness for the rare but possibly underdiagnosed disease.