Background: MS is common in people of northern European ethnicity who live
in northern geographic areas; however, MS is rarely identified among aborig
inal peoples living in the same areas. Objectives: To determine the prevale
nce, clinical features, HLA type, and viral infections associated with MS a
mong aboriginals in Manitoba, Canada. Methods: A retrospective study was pe
rformed in which the clinical features of all aboriginal patients with MS t
ogether with HLA type and human herpesvirus-6, HTV-1, human T-cell lymphotr
opic virus-1, and endogenous retrovirus associated with MS (MSRV) infection
s were analyzed and compared with results from nonaboriginal patients with
MS. Results: Seven aboriginals with MS were identified with a period preval
ence among aboriginals of 40:100,000. Clinical features included relapsing-
remitting (n = 6) or primary progressive (n = 1) phenotypes with aggressive
disease courses and frequent involvement of optic nerves and spinal cord (
n = 5) compared with nonaboriginal patients. Autopsy of one patient showed
necrosis and eosinophil infiltrates in a cervical spinal cord lesion and a
demyelinated optic nerve. Analysis of HLA alleles at the DRB1 and DQB1 loci
indicated that the HLA types detected were common in aboriginals, but ther
e were no HLA alleles previously associated with the development of MS. Ana
lysis of the copy number of MRSV did not show differences among aboriginals
and nonaboriginals with or without MS. Conclusions: Aboriginals of Algonki
an background are at increased risk for an aggressive type of MS, resemblin
g neuromyelitis optica, which is resistant to conventional MS treatments an
d occurs independently of HLA alleles previously associated with MS.