It has been suggested that patients with giant cell arteritis (GCA) may share a common pathway with atherosclerosis. Furthermore, patients with GCA and polymyalgia rheumatica (PMR), in addition to advanced age, are treated for prolonged periods of time with corticosteroids, a factor that can also accelerate atherosclerosis. Hyperhomocysteinaemia is considered an independent risk factor for atherosclerosis, and might play a role in ischaemic manifestations that occur with a variable frequency during the course of GCA. The purposes of the present study were: (i). to analyse the plasma levels of homocysteine in patients with GCA and PMR, (ii). to determine the influence of corticosteroid therapy on the homocysteine levels and (iii). to analyse if the levels of homocysteine may predict the development of ischaemic complications in patients with GCA.
Plasma homocysteine concentration was measured in 56 patients with active PMR/GCA (17 GCA and 39 isolated PMR) before steroid treatment and 23 healthy age-matched volunteers were used as controls. The total plasma homocysteine level was quantified using a fluorescent polarization immunoassay.
Homocysteine concentrations were higher in PMR and GCA patients than age-matched controls (P < 0.05). Patients with GCA had slightly higher levels of plasma homocysteine than those with isolated PMR (13.6+/-4.3 vs 12.7+/-3.1 micromol/l, P=0.6). In 30 of these patients (12 GCA and 18 PMR) a second measurement of homocysteine concentration was done when they were in clinical remission with steroid treatment. The post-treatment levels of homocysteine were significantly increased in GCA rather than in PMR patients. In 13 patients with homocysteine levels above the normal upper limit of our laboratory, therapy with folic acid and/or vitamin B12 was started. After 3 months of vitamin supplements, the homocysteine concentration significantly decreased from 19.2+/-3.1 to 13.6+/-3.2 micromol/l (P=0.001). Such decrease was less marked in the PMR than in GCA patients. Ten out of the 17 patients with GCA had ischaemic manifestations of the disease. The levels of homocysteine were slightly higher in GCA patients with ischaemia than in those without ischaemic manifestations, although the difference did not reach statistical significance (15+/-4.9 vs 11.6+/-1.9 micromol/l, P=0.46).
Patients with active PMR and GCA had elevated plasma concentrations of homocysteine. Corticosteroid therapy significantly increased such levels, especially in GCA patients. Treatment with supplements of folic acid and/or vitamin B12 reduced the homocysteine concentrations. These data support the hypothesis that patients with GCA (and to a lesser extend PMR patients) may share a common pathway with atherosclerosis and suggest a new atherogenic mechanism of corticosteroids.