AQP4+ NMOSD has also been associated with specific human leukocyte antigen (HLA) alleles, as well as other autoimmune disorders such as systemic lupus erythematosus.^1,2 Additional risk factors that have been suggested to play a role in NMOSD include smoking and infections.^1,2

AQP4-IgG positive NMOSD often coexists with other autoimmune diseases, such as Sjögren’s syndrome, systemic lupus erythematosus or myasthenia gravis (MG).^1,3,4 The reason these diseases occur together is unclear, but it could be related to a predisposing genetic background, environmental factors or shared pathological mechanisms.⁴ Patients with NMOSD can also have other non-autoimmune diseases, such as diabetes, hypertension and cardiovascular disease.⁴ A study examining the frequency of comorbidities among individuals with NMOSD also noted that psychiatric disorders – such as general anxiety disorder and major depressive disorders – were more common in NMOSD patients, possibly due to the chronic neuropathic pain and fatigue.⁵ It has been suggested that some of the non-autoimmune comorbidities, such as hyperglycemia and diabetes, could result from corticosteroid treatment of NMOSD used to suppress inflammation during relapses.⁴