Spondylitis, Ankylosing: A chronic inflammatory condition affecting the axial joints, such as the SACROILIAC JOINT and other intervertebral or costovertebral joints. It occurs predominantly in young males and is characterized by pain and stiffness of joints (ANKYLOSIS) with inflammation at tendon insertions.Spondylitis: Inflammation of the SPINE. This includes both arthritic and non-arthritic conditions.HLA-B27 Antigen: A specific HLA-B surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-B*27 allele family.Sacroiliac Joint: The immovable joint formed by the lateral surfaces of the SACRUM and ILIUM.Spine: The spinal or vertebral column.Spondylarthritis: Inflammation of the joints of the SPINE, the intervertebral articulations.Antirheumatic Agents: Drugs that are used to treat RHEUMATOID ARTHRITIS.Spondylarthropathies: Heterogeneous group of arthritic diseases sharing clinical and radiologic features. They are associated with the HLA-B27 ANTIGEN and some with a triggering infection. Most involve the axial joints in the SPINE, particularly the SACROILIAC JOINT, but can also involve asymmetric peripheral joints. Subsets include ANKYLOSING SPONDYLITIS; REACTIVE ARTHRITIS; PSORIATIC ARTHRITIS; and others.Blood Sedimentation: Measurement of rate of settling of erythrocytes in anticoagulated blood.ArthritisIritis: Inflammation of the iris characterized by circumcorneal injection, aqueous flare, keratotic precipitates, and constricted and sluggish pupil along with discoloration of the iris.Severity of Illness Index: Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder.Tuberculosis, Spinal: Osteitis or caries of the vertebrae, usually occurring as a complication of tuberculosis of the lungs.Arthritis, Reactive: An aseptic, inflammatory arthritis developing secondary to a primary extra-articular infection, most typically of the GASTROINTESTINAL TRACT or UROGENITAL SYSTEM. The initiating trigger pathogens are usually SHIGELLA; SALMONELLA; YERSINIA; CAMPYLOBACTER; or CHLAMYDIA TRACHOMATIS. Reactive arthritis is strongly associated with HLA-B27 ANTIGEN.Arthritis, Psoriatic: A type of inflammatory arthritis associated with PSORIASIS, often involving the axial joints and the peripheral terminal interphalangeal joints. It is characterized by the presence of HLA-B27-associated SPONDYLARTHROPATHY, and the absence of rheumatoid factor.Rheumatic Diseases: Disorders of connective tissue, especially the joints and related structures, characterized by inflammation, degeneration, or metabolic derangement.Balneology: Therapy by various hot or warm baths in natural mineral waters, spas, or "cures". It includes not only bathing in, but also drinking the waters, but it does not include whirlpool baths (HYDROTHERAPY).Uveitis, Anterior: Inflammation of the anterior uvea comprising the iris, angle structures, and the ciliary body. Manifestations of this disorder include ciliary injection, exudation into the anterior chamber, iris changes, and adhesions between the iris and lens (posterior synechiae). Intraocular pressure may be increased or reduced.Lumbar Vertebrae: VERTEBRAE in the region of the lower BACK below the THORACIC VERTEBRAE and above the SACRAL VERTEBRAE.Kyphosis: Deformities of the SPINE characterized by an exaggerated convexity of the vertebral column. The forward bending of the thoracic region usually is more than 40 degrees. This deformity sometimes is called round back or hunchback.Arthritis, Rheumatoid: A chronic systemic disease, primarily of the joints, marked by inflammatory changes in the synovial membranes and articular structures, widespread fibrinoid degeneration of the collagen fibers in mesenchymal tissues, and by atrophy and rarefaction of bony structures. Etiology is unknown, but autoimmune mechanisms have been implicated.Thoracic Vertebrae: A group of twelve VERTEBRAE connected to the ribs that support the upper trunk region.HLA Antigens: Antigens determined by leukocyte loci found on chromosome 6, the major histocompatibility loci in humans. They are polypeptides or glycoproteins found on most nucleated cells and platelets, determine tissue types for transplantation, and are associated with certain diseases.Cervical Vertebrae: The first seven VERTEBRAE of the SPINAL COLUMN, which correspond to the VERTEBRAE of the NECK.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Osteitis: Inflammation of the bone.Sulfasalazine: A drug that is used in the management of inflammatory bowel diseases. Its activity is generally considered to lie in its metabolic breakdown product, 5-aminosalicylic acid (see MESALAMINE) released in the colon. (From Martindale, The Extra Pharmacopoeia, 30th ed, p907)Anti-Inflammatory Agents, Non-Steroidal: Anti-inflammatory agents that are non-steroidal in nature. In addition to anti-inflammatory actions, they have analgesic, antipyretic, and platelet-inhibitory actions.They act by blocking the synthesis of prostaglandins by inhibiting cyclooxygenase, which converts arachidonic acid to cyclic endoperoxides, precursors of prostaglandins. Inhibition of prostaglandin synthesis accounts for their analgesic, antipyretic, and platelet-inhibitory actions; other mechanisms may contribute to their anti-inflammatory effects.Back Pain: Acute or chronic pain located in the posterior regions of the THORAX; LUMBOSACRAL REGION; or the adjacent regions.Pseudarthrosis: A pathologic entity characterized by deossification of a weight-bearing long bone, followed by bending and pathologic fracture, with inability to form normal BONY CALLUS leading to existence of the "false joint" that gives the condition its name. (Dorland, 27th ed)Receptors, Tumor Necrosis Factor: Cell surface receptors that bind TUMOR NECROSIS FACTORS and trigger changes which influence the behavior of cells.Spinal DiseasesTreatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Sacroiliitis: Inflammation of the SACROILIAC JOINT. It is characterized by lower back pain, especially upon walking, fever, UVEITIS; PSORIASIS; and decreased range of motion. Many factors are associated with and cause sacroiliitis including infection; injury to spine, lower back, and pelvis; DEGENERATIVE ARTHRITIS; and pregnancy.Antibodies, Monoclonal: Antibodies produced by a single clone of cells.Klebsiella: A genus of gram-negative, facultatively anaerobic, rod-shaped bacteria whose organisms arrange singly, in pairs, or short chains. This genus is commonly found in the intestinal tract and is an opportunistic pathogen that can give rise to bacteremia, pneumonia, urinary tract and several other types of human infection.Psoas Abscess: Abscess of the PSOAS MUSCLES resulting usually from disease of the lumbar vertebrae, with the pus descending into the muscle sheath. The infection is most commonly tuberculous or staphylococcal.