HLA-B27 and modified bone formation

Molecular mimicry and autoimmune thyroid disease

Hypothesized 40 years ago, molecular mimicry has been thereafter demonstrated as an extremely common mechanism by which microbes elude immune response and modulate biosynthetic/metabolic pathways of the host. In genetically predisposed persons and under particular conditions, molecular mimicry between microbial and human antigens can turn a defensive immune response into autoimmunity. Such triggering role and its pathogenetic importance have been investigated and demonstrated for many autoimmune diseases. However, this is not the case for autoimmune thyroid disease, which appears relatively neglected by this field of research. Here we review the available literature on the possible role of molecular mimicry as a trigger of autoimmune thyroid disease. Additionally, we present the results of in silico search for amino acid sequence homologies between some microbial proteins and thyroid autoantigens, and the potential pathogenetic relevance of such homologies. Relevance stems from the overlap with known autoepitopes and the occurrence of specific HLA-DR binding motifs. Bioinformatics data published by our group support and explain the triggering role of Borrelia, Yersinia, Clostridium botulinum, Rickettsia prowazekii and Helicobacter pylori. Our new data suggest the potential pathogenic importance of Toxoplasma gondii, some Bifidobacteria and Lactobacilli, Candida albicans, Treponema pallidum and hepatitis C virus in autoimmune thyroid disease, indicating specific molecular targets for future research. Additionally, the consistency between in silico prediction of cross-reactivity and experimental results shows the reliability and usefulness of bioinformatics tools to precisely identify candidate molecules for in vitro and/or in vivo experiments, or at least narrow down their number.

COL6A1, the candidate gene for ossification of the posterior longitudinal ligament, is associated with diffuse idiopathic skeletal hyperostosis in Japanese

STUDY DESIGN

Genetic screening of collagen 6A1 gene (COL6A1) in patients with diffuse idiopathic skeletal hyperostosis (DISH) recruited in Japan and the Czech Republic.

OBJECTIVE

To investigate allelic associations between DISH and nucleotide variants of COL6A1.

SUMMARY OF BACKGROUND DATA

DISH is a skeletal hyperostotic disease characterized by ligamentous ossification of the anterolateral side of the spine. Ossification of the posterior longitudinal ligament (OPLL) is a related disorder with DISH, and COL6A1 was identified as a susceptibility gene to OPLL. COL6A1 was examined for susceptibility in DISH patients from Japan and the Czech Republic.

METHODS

Seven single nucleotide polymorphisms of COL6A1 were genotyped by direct sequencing. The allele frequencies were compared between 97 Japanese DISH patients and 298 Japanese controls, and between 96 Czech DISH patients and 96 Czech controls by chi2 test.

RESULTS

The intron 32 (-29) single nucleotide polymorphisms of COL6A1 was significantly associated with the Japanese DISH patients (chi2 = 9.33; P = 0.0022), but not with the Czech DISH patients.

CONCLUSIONS

Because COL6A1 could be a susceptibility to the occurrence of DISH and OPLL in the Japanese population, we consider that COL6A1 could be responsible for the hyperostotic state, leading to ectopic bone formation in the spinal ligament.

Elbow heterotopic ossification in head-trauma patients: diagnosis and treatment

Heterotopic ossification is a disorder characterized histologically and radiographically by normal bone formation in soft tissues that normally have no ossification properties. In severe head-trauma patients, a high incidence of heterotopic ossification occurs. The diagnosis of this pathology in these patients often is difficult for residual neurological damage. The etiology of heterotopic ossification following head trauma is unknown. Similarities have been found between heterotopic ossification and myositis ossificans, a hereditary autosomal dominant disease.

A controlled study of diffuse idiopathic skeletal hyperostosis. Clinical features and functional status

Diffuse idiopathic skeletal hyperostosis (DISH) is a common but little-studied disorder in the elderly that is infrequently recognized by physicians. Its prevalence in adults over 40 years of age is estimated at 3.8% for men and 2.6% for women. The present case-control study evaluated the history of pain and stiffness, radicular pain and enthesitis, physical findings on the musculoskeletal examination, and level of physical and psychologic disability in 130 persons: 56 patients with DISH, 43 control patients with spondylosis of the lumbar spine, and 31 healthy control patients. DISH patients were more likely to report a past history of upper extremity pain, medial epicondylitis of the elbow, enthesitis of the patella or heel, or dysphagia than spondylosis patients. They had more extremity and spinal stiffness and pain than healthy controls. DISH patients weighed more at a young age and their body mass index was greater at the time of the clinical evaluation than either spondylosis or healthy control patients. On musculoskeletal examination, DISH patients had a greater reduction in neck rotation and thoracic movements than either spondylosis patients or healthy controls, and had a greater reduction in lumbar movement than healthy controls. DISH patients had similar levels of spinal disability and physical disability overall, as measured by standardized indices, as spondylosis patients. No differences were found among the 3 groups of patients for the laboratory tests evaluated. DISH is clearly a distinct disorder with signs and symptoms that distinguish it from other causes of spinal complaint and from healthy individuals. It has the potential to cause major disability. Future studies need to address the natural history of DISH, pursue pathogenic mechanisms, and evaluate treatment modalities.

Insulin and new bone formation in diffuse idiopathic skeletal hyperostosis

The tendency of patients with DISH towards obesity or an adult onset of diabetes has been reflected in marked hyperinsulinaemia following glucose challenge. It is hypothesized that insulin at prolonged and high physiologic levels promotes new bone growth, particularly in the entheseal regions. These areas are also subject to various mechanical forces. The resulting new bone produces the radiological changes which characterise DISH.

Ankylosing hyperostosis in American blacks: a longitudinal study

We studied 63 consecutive patients with ankylosing hyperostosis to investigate any possible difference in clinical or roentgenographic features between whites and blacks. Our data suggest that (a) the disease may not be less common among blacks, (b) presence of extraspinal hyperostosis in this disease may be more frequent in black patients, and (c) the known male preponderance of the disease among whites may not occur among blacks.

HLA-B27-associated spondyloarthritis and enthesopathy in childhood: clinical, pathologic, and radiographic observations in 58 patients

HLA-B27 typing of all arthritic children helped to identify and focus attention on a subset whose disease was pathogenetically related to and demonstrated clinical features of ankylosing spondylitis and Reiter syndrome, but only rarely fulfilled current diagnostic criteria for those disorders (spondyloarthritis). In contrast to other forms of childhood arthritis, enthesopathy (inflammation at the sites of attachment of ligaments and tendons to bone) was a prominent feature in 75%; a family history of similar arthritis was obtained from 60%; boys were more frequently affected (2:1); urethritis, acute iritis, conjunctivitis, or keratoderma blennorrhagicum occurred at some time in 42%; and the initial attack followed an unexplained febrile illness, known dysentery or urethritis, or severe musculoskeletal trauma in 41%. The arthritis was generally pauciarticular, asymmetric, and primarily in the feet and large joints of the lower extremities. Distinctive radiographic features included periostitis, severe osteopenia, calcaneal erosions, and heel spurs; three of 58 had rapid destruction of a single joint. Only ten patients (all boys) were found to have radiographic sacroiliitis after an average of five years of disease, and only three had the Reiter triad. The lifetime risk of sacroiliitis and spinal ankylosis can only be determined by long-term follow-up of such prospectively identified groups of spondyloarthritic children.

Calcified periarthritis at multiple sites including lumbar intervertebral discs. Report of a case

A case with calcified periarthritis at peripheral sites and calcification in intervertebral discs gives support to the perception of a distinct disease entity as proposed by SANDSTROM. The possible significance of genetic factors is discussed.

Vertebral ankylosing hyperostosis (Forestier's disease) and HLA antigens in Pima Indians

Vertebral ankylosing hyperostosis is a common skeletal disorder among Pima Indians. Prevalence rates of approximately 50% have been reported in Pima Indian males aged 44 or older. The HLA-B27 antigen is also found more commonly in Pima Indians than in Caucasians (18% versus 6%). Because of the increased prevalence of both vertebral ankylosing hyperostosis and HLA-B27 in Pima Indians, a possible association between the two was thought to exist. Therefore, histocompatibility testing was done on 44 adult male Pima Indians age 55 or older with classic vertebral ankylosing hyperostosis and 33 age-matched controls. No significant association between any histocompatibility antigen phenotype or haplotype and vertebral ankylosing hyperostosis was found. This disease, therefore, connot be classified with the HLA-B27 associated spondylarthropathies.

Ankylosing spondylitis with subsequent development of rheumatoid arthritis, Sjögren's syndrome, and rheumatoid vasculitis

Twelve years after the onset of ankylosing spondylitis, a patient developed severe seropositive rheumatoid arthritis with subcutaneous nodules. This was subsequently complicated by Sjögren's syndrome and rheumatoid vasculitis. The literature is reviewed, and the nature of the association between ankylosing spondylitis and rheumatoid arthritis is discussed.

HLA and kidney stone disease

Normocalcemic patients with recurring kidney stones were HLA typed. 54 patients with an idiopathic high urinary excretion of calcium but without signs of renal tubular defect showed a B27 phenotype frequency which was more than twice that of the controls and a CW1 frequency that was doubled. After correction for the number of tested HLA specificities the increase was not significant. 35 patients with renal tubular acidosis and 16 patients with no metabolic diagnosis had no deviant HLA antigen distribution.