Multiple sclerosis (MS) has a positive association with young-adult onset Hodgkin lymphoma (YAHL) due to common environmental and inherited risks, according to the study “Multiple sclerosis and risk of young-onset Hodgkin lymphoma” published in the Neuroimmunology and Neuroinflamation journal.

Although MS has been associated with an overall reduction of cancer risk in patients from Sweden, a positive association between MS and Hodgkin lymphoma (HL) may exist, possibly due to shared inherited or environmental causes, such as exposure to Epstein-Barr virus in childhood. A previous Danish study identified familial association of MS and YAHL, a phenotype of Hodgkin lymphoma that occurs at ages 15-39 years, leading researchers to hypothesize that MS was only associated with YAHL but not other HL phenotypes.

To test their hypothesis, the research team led by Shahram Bahmanyar, PhD, analyzed 29,617 patients from the Swedish general population with an MS diagnosis between 1968 and 2012, and 296,164 patients without MS, and assessed the occurrence of HL among each group.

Results revealed that 4 patients with MS developed YAHL, compared to 16 patients in the non-MS group, demonstrating that MS patients are 3.3 times more likely to be diagnosed with YAHL, but not with older-onset HL. Furthermore, all of the 4 YAHL diagnosis in MS patients occurred in women, who have a risk of developing YAHL four times higher when diagnosed with MS.

Although previous studies have proposed shared susceptibility to MS and HL is in part due to genetic factors, such as the HLA DR2 allele, other possible causes may be linked to common patterns of childhood exposure to microorganisms, suggesting that infectious causes may be shared in both diseases. However, the authors explain that they were not able to identify specific childhood exposures that could underlie the association, possibly due to the lack of relevant personal characteristics, such as ethnic origin, that may have limited their study.

“The association of MS with YAHL indicates shared inherited or acquired risks for these diseases, which are not necessarily mutually exclusive,” the authors conclude in their study. “Although the study cannot demonstrate which exposures are responsible, they might include some previously identified shared putative factors, such as pattern of childhood infectious exposures.”