Primary central nervous system lymphoma (PCNSL) is a rare (incidence rate of 0.6 cases per 100,000 person years) non-Hodgkin lymphoma (NHL) found in the brain, spinal cord, and leptomeninges.1,2 PCNSL is most commonly seen in patients who are immunosuppressed, such as those with human immunodeficiency virus (HIV) or who are post-solid organ transplantation. In addition, Epstein-Barr Virus (EBV) has been implicated in the pathogenesis of PCSNL in these immunosuppressed patients.3 The underlying pathophysiology to explain exactly why immunosuppressed patients are at greater risk is not completely understood, although it has been postulated that it could be related to the patient’s immunosuppressive medication, or the disease state itself.

Although the incidence rates of PCNSL are relatively low, recent data from the United States Surveillance, Epidemiology, and End Results (US SEER) study from 1992 to 2011 have shown that the rates have increased up to 1.7% in both men and women 65 years or older, even when immunosuppressed patients were excluded.2 This is not the case for other NHLs in similar populations, where rates plateaued in 2004.4 Patients can present with a flu-like prodrome along with gastrointestinal symptoms such as nausea, vomiting and/or diarrhea along with nonspecific neurological complaints such as headache, fatigue, and back pain.5

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One possible explanation of this increased incidence in nonimmunosuppressed patients is the eventual development of autoimmune conditions along with their respective treatments. Recently a research team led by Mahale and colleagues reviewed the SEER-Medicare database to further investigate this increased incidence.3 

The study was conducted retrospectively using a case-control design to identify 1727 patients with PCNSL from 1992 to 2015. These patients were compared with 200,000 control patients during the same time period. The authors surveyed these patients for the presence of any of 31 autoimmune conditions, provided these autoimmune disorders were diagnosed at least 12 months prior to the PCNSL diagnosis. The autoimmune conditions of interest included rheumatoid arthritis, systemic lupus erythematosus (SLE), psoriasis, ulcerative colitis, polyarteritis nodosa (PAN), autoimmune hepatitis (AIH), and myasthenia gravis (MG), among others.