Prevalence of thyroid autoantibodies in patients with systematic autoimmune rheumatic diseases. Cross-sectional study

ABSTRACT BACKGROUND: Thyroid autoimmunity is more common in patients with rheumatic diseases than in healthy populations. The degree of association seems subject to influence from patients' geographical location. Here, we aimed to ascertain the prevalence of thyroid autoantibodies in a cohort of patients with systemic rheumatic disease and the degree of association between its presence and inflammatory activity. DESIGN AND SETTING: Cross-sectional observational study in a rheumatology unit. METHODS: 301 patients with systemic lupus erythematosus (SLE), 210 with rheumatoid arthritis (RA), 58 with scleroderma (SSc) and 80 with spondyloarthritis (SpA) were studied regarding thyroid function (TSH and T4), anti-thyroglobulin (TgAb) and anti-thyroperoxidase (TPOab) and compared with 141 healthy controls. Disease activity in patients with rheumatic disease was assessed through appropriate indexes. RESULTS: There were more antithyroid antibodies in SLE patients with hypothyroidism (P = 0.01; odds ratio, OR 2.7; 95% confidence interval, CI: 1.20-6.26) and in those without hypothyroidism (P = 0.06; OR 2.4; 95% CI: 1.28-4.55) than in controls. SSc patients also showed: P = 0.03 both with antithyroid antibodies and hypothyroidism (OR 3.4; 95% CI: 1.06-10.80) and without hypothyroidism (OR 3.1; 95% CI: 1.11-0.13). RA and SpA patients had the same prevalence as controls (P not significant). Presence of autoantibodies with and without hypothyroidism was not associated with the activity or functional indexes evaluated. CONCLUSION: SLE and SSc were associated with higher prevalence of thyroid autoantibodies in patients with and without hypothyroidism, unlike SpA and RA. There was no link between thyroid autoantibody presence and disease activity or functional impairment.

Comprendiendo la inmunopatogenia de las artropatías seronegativas / Understanding the immunopathogenesis of seronegative arthropathy

Las artropatías seronegativas o espondiloartropatías corresponden a un grupo de enfermedades que comparten características clínicas y genéticas, asociadas fuertemente con el complejo mayor de histocompatibilidad clase I HLA-B27. El rol patogénico del HLA-B27 es desconocido; se han propuesto múltiples teorías, entre las cuales cabe destacar tres: 1) péptido artritogénico, 2) cadenas pesadas aberrantes en la superficie celular y 3) estrés en el retículo endoplásmico rugoso. Es conocido que los linfocitos T CD4 tienen un rol primordial en esta patología. Se ha encontrado que en la mayoría de estas artropatías hay una gran producción de citoquinas del perfil Th1, sobre todo de TNF alfa, el que jugaría un rol crucial, pues se ha visto que con los fármacos anti TNF se produce una mejoría en la mayoría de estas patologías.

Seronegative arthropathies or spondyloarthropathy belong to a group of diseases that share clinical and genetic characteristics associated strongly with major histocompatibility complex class I HLA-B27. The pathogenic role of HLA-B27 is unknown, many theories have been proposed, among which we highlight three: 1) arthritogenic peptides, 2) aberrant heavy chains on the cell surface and 3) stress on the rough endoplasmic reticulum. It is known that CD4 T lymphocytes have a pivotal role in this pathology. A great production of Th1 profile cytokines have been found to exist in most of these arthropathies, especially TNF alpha., which may play a crucial role, since anti-TNF drugs have been known to produce an improvement in most of these pathologies.