Ankylosing spondylitis (AS) is a chronic systemic inflammatory disorder affecting the axial skeleton, peripheral joints, entheses, eyes, skin, and intestines. It is characterized by inflammatory back pain, radiographic sacroiliitis, excess spinal bone formation, and a high prevalence of human leukocyte antigen (HLA)-B27. Clinical manifestations of ankylosing spondylitis include back pain, progressive spinal rigidity, and inflammation of the hips, shoulders, peripheral joints, and fingers or toes.

Autoinflammatory diseases, commonly called systemic autoinflammatory diseases, are a group of disorders mediated by dysfunction of the innate immune system, wherein the innate immune response is activated without an apparent trigger, leading to hyperinflammation.

Septic arthritis can have bacterial, fungal, mycobacterial, or viral etiologies. Streptococcus aureus is the most common bacterial pathogen in both children and adults. Commonly-affected joints are the hip joint in children and the knee in adults.

Behcet disease — also known as Behcet’s syndrome, Behcet’s vasculitis, Adamantiades-Behcet’s syndrome, and Silk Road disease — is a chronic inflammatory disorder that can affect multiple systems throughout the body. The most common symptoms include mouth sores, skin lesions, and eye inflammation, but the disease can also cause joint pain, gastrointestinal problems, and neurological symptoms.

Calcium pyrophosphate deposition (CPPD) disease, also known as chondrocalcinosis, is a form of arthritis caused by CPP crystals. It involves the synovial and perarticular tissues and is characterized by painful swelling it at least 1 joint.

Central nervous system (CNS) vasculitis is the inflammation of blood vessels in the brain and spinal cord. Primary CNS vasculitis can be triggered by bacteria, viruses, or connective tissue disorders. Secondary CNS vasculitis can be triggered by bacteria, viruses, or fungi.

Degenerative disc disease incorporates multiple conditions, including spinal compression, pinched nerve, and back or neck pain. Lumbar degenerative disc disease is the most common cause of lower back pain in the world. Cervical degenerative disc disease can cause neck pain and radiating arm pain.

Lupus, a chronic inflammatory autoimmune disease, has multiple etiologies. Drug-induced lupus, a subtype of lupus caused by specific drugs triggering the production of autoantibodies, can be further categorized as drug-induced subacute cutaneous lupus, drug-induced systemic lupus, and drug-induced chronic cutaneous lupus.

Ehlers-Danlos syndrome is a group of inherited connective tissue disorders that primarily affects the skin, joints, and blood vessel walls1 but can affect every organ system and result in significant morbidity and mortality. Typical clinical manifestations are skin hyperelasticity, hypermobility of joints, the fragility of blood vessels, and atrophic scarring. Hypermobility Ehlers-Danlos syndrome (formerly known as Ehlers-Danlos syndrome type 3) and classical Ehlers-Danlos syndrome are the two most common subtypes.

Facet hypertrophy, also known as facet joint hypertrophy, occurs when facet joints in the spine are enlarged as a result of injury, arthritis, or increasing age.

Giant cell arteritis (GCA), also known as temporal arteritis, is a granulomatous vasculitis that mostly affects large- and medium-sized arteries, particularly the branches of the proximal aorta. Giant cell arteritis is the most frequent systemic vasculitis involving large and medium vessels, with advanced age being the most significant risk factor.

Medial epicondylitis (ME), also known as Golfer’s elbow, is caused by damage to the muscles and tendons that control the wrist and fingers. The damage is typically related to excess or repeated stress — especially forceful wrist and finger motions.

Gout is the most common type of inflammatory arthritis in the world. Dietary, environmental, and genetic factors appear to play a role in disease pathogenesis which is reflected in the varying distributions of prevalence by region and demographic factors. Age is a major factor affecting prevalence, with rates increasing over the entire lifespan in men and after menopause in women.

Granulomatosis with polyangiitis (GPA), also known as Wegener granulomatosis, is a type of anti-neutrophil cytoplasmic antibody-associated (ANCA)-associated small vessel vasculitides. It is a severe autoimmune disease that affects the upper and lower respiratory system and kidneys.

Hemochromatosis, a disorder where the body accumulates excess iron, can affect the skin, heart, liver, pancreas, pituitary gland, and joints. Etiology is linked to the autosomal recessive inheritance of the HFE protein. Laboratory anomalies include raised serum ferritin and transferrin saturation.

A typically uniarticular condition, hydroxyapatite (HA) crystal deposition disease (HADD) is marked by the presence of hydroxyapatite crystals in the periarticular soft tissues, especially the tendons. HA is a mineral found in normal bone, but when it builds up in and around the joints it can cause inflammation, tenderness, and pain.

Hyperparathyroidism is broken into 2 main subcategories: primary and secondary hyperparathyroidism. Primary hyperparathyroidism is a common endocrine disorder of calcium metabolism characterized by hypercalcemia and elevated concentrations of the parahyroid hormone. Secondary hyperparathyroidism is the increased secretion of parathyroid hormone triggered by hypocalcemia, hyperphosphatemia, or decreased active vitamin D.

Hypothyroidism occurs when this hormone is in short supply, which causes body processes to slow down, resulting in a constellation of symptoms, including joint pain.

Large-vessel vasculitis is an umbrella term for diseases that affect the large arteries. The two main types are giant cell arteritis and Takayasu arteritis. There are other forms of large-vessel vasculitis that do not have specific names, such as idiopathic isolated aortitis.

Leukocytoclastic vasculitis (LCV), a type of small vessel vasculitis, affects the skin and organs due to inflammation caused by neutrophils. It is a histopathological phenomenon seen in various disease states.

Medium-vessel vasculitis affects medium-sized arteries. The two main types of medium-size vessel vasculitis are polyarteritis nodosa and Kawasaki disease.

Microscopic polyangiitis (MPA) vasculitis is a rare type of vasculitis that causes inflammation in the body’s small to medium-sized blood vessels.1 This inflammation causes decreased blood flow to the body’s organs and tissues. MPA vasculitis typically affects the nerves, kidneys, joints, lungs, and skin.

Derived from the Greek word “ochre,” meaning pale yellow, ochronosis is a rare disease characterized by a blue-black or gray-blue pigmentation. It is caused by deposits of yellow or ochre-colored pigment and typically affects the skin, the cartilage of the ears, and eye sclerae.

Osteoarthritis, the leading form of arthritis, is a chronic degenerative disorder characterized by articular cartilage and periarticular bone remodelling. It affects weight-bearing joints, particularly the knee and hip. Osteoarthritis can present as localized, generalized, or erosive osteoarthritis.

Patellar tendonitis presents with a history of activity-related anterior knee pain. Symptoms initially appear after sports activity, particularly sports involving jumping. Repetitive loading over a single session or with insufficient rest between sessions leads to tears and altered mechanics of the tendon.

Psoriatic arthritis (PsA) is a chronic inflammatory joint condition that can develop in patients with psoriasis. Inflammatory musculoskeletal characteristics in the joints, entheses, or spine are most commonly identified in skin or nail psoriasis. A hallmark characteristic is the absence of rheumatoid factor and anti-cyclic citrullinated peptide.

Raynaud disease, also known as Raynaud’s phenomenon, typically affects distal areas such as the fingers. It is a rare disorder that affects the cutaneous arterioles and can cause them to abnormally vasoconstrict, temporarily limiting blood flow. The most common symptoms are episodes of coldness, numbness, and tingling in the fingers or toes.

Scleroderma is an umbrella term for a heterogeneous group of rheumatic disorders; it includes several fibrosing conditions with varying features and management. Scleroderma is a chronic connective tissue and autoimmune disorder that has immune dysfunction, vasculopathy, tissue fibrosis, and inflammation as the main underlying pathologic processes.

Sjogren’s syndrome is a chronic autoimmune condition caused by lymphocytic infiltration into the exocrine glands and other organs. It is characterized by dry mouth and dry eyes from involvement of the salivary and lacrimal glands as well as a variety of extraglandular manifestations.

Small-vessel vasculitis is the umbrella name for a group of rare diseases characterized by inflammation of smaller blood vessels, such as arterioles, venules, and capillaries.