Vitamin D deficiency in patients with primary immune-mediated peripheral neuropathies

T cells are important in the immunopathology of immune-mediated peripheral neuropathies (PNP) and activated vitamin D regulates the immune response through increasing the amount of regulatory T cells. An association between vitamin D deficiency and polyneuropathy has been stipulated; hence we assessed whether patients with primary immune-mediated PNP have low vitamin D [25(OH)D] levels.

Plasma levels of 25(OH)D were analyzed in 26 patients with primary immune-mediated PNP, 50 healthy matched blood donors and 24 patients with motor neuron disease (MND). INCAT score was assessed in patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy. ALSFRS-R score was applied to MND patients and the modified Rankin (mRankin) scale compared disability among patient groups.

Mean 25(OH)D value in PNP patients was 40 ± 16 nmol/l, compared to 69 ± 21 nmol/l in healthy blood donors (p<0.001). MND patients had a higher mean 25(OH)D than PNP patients (59 ± 26 nmol/L; p=0.006) and comparable levels to healthy blood donors (p=0.15). Mean 25(OH)D value was not higher in PNP patients with pre-existing vitamin D3 supplementation of 800 IU/day (N=6; 35 ± 18 nmol/L) than in unsupplemented PNP patients (42 ± 16 nmol). INCAT score ranged from 0 to 10 (mean 3.5) and ALSFRS-R ranged from 11 to 44 (mean 31). mRankin score was more severe in MND patients (mean 3.5) compared to PNP patients (mean 2.1).

All patients with primary immune-mediated PNP were diagnosed with vitamin D deficiency and they had significantly lower 25(OH)D values than healthy control persons and MND patients. We suggest monitoring of vitamin D status in patients with autoimmune PNP, since immune cells are responsive to the ameliorative effects of vitamin D.