Overview Cryoglobulinaemic vasculitis is an immune complex–mediated small to medium vessel vasculitis caused by circulating cryoglobulins—immunoglobulins that precipitate below 37 °C and redissolve on warming. These immune complexes deposit in vessel walls, activate complement (typically with marked C4 consumption), and drive leukocytoclastic vasculitis. “Mixed” CV (types II and III) is most often linked to hepatitis […]

Overview Sarcoidosis is a multisystem granulomatous disease of unknown cause, characterised by the formation of non‑caseating granulomas in affected organs. Pulmonary involvement occurs in ~90% of patients, making it the most common manifestation. Global prevalence varies widely (e.g., 3.7/100,000 in Japan vs. 28.2/100,000 in Finland), with higher rates in Black Americans and Northern Europeans. Peak […]

Overview Rheumatoid pleural effusion (RPE) is an uncommon extra‑articular manifestation of rheumatoid arthritis (RA), occurring in ~2–5% of patients, more often in middle‑aged men with high rheumatoid factor (RF) titres, despite RA being more common in women. It typically presents during active disease or in patients with rheumatoid nodules, but can occasionally precede joint symptoms. […]

Overview Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is a serious extra-articular manifestation of RA, affecting up to 10% of RA patients clinically, though subclinical involvement may be present in up to 60% on HRCT. It typically presents in the 5th–6th decade, with a male predominance and is a leading cause of RA-related mortality. The most […]

Overview Sjögren’s-associated interstitial lung disease (Sjögren’s-ILD) is a significant extra-glandular manifestation of primary Sjögren’s disease (pSS), occurring in ~9–20% of patients clinically, with subclinical involvement detectable in up to 50% on HRCT. It may precede sicca symptoms or develop late in the disease course. The most common ILD pattern is nonspecific interstitial pneumonia (NSIP), followed […]

Overview Systemic sclerosis–associated interstitial lung disease (SSc-ILD) is one of the most common and severe internal organ manifestations of systemic sclerosis (SSc), occurring in up to 50–60% of patients on HRCT, with clinically significant disease in ~25–30%. It is a major cause of SSc-related mortality. The most frequent histopathological pattern is nonspecific interstitial pneumonia (NSIP), […]

Overview Microscopic polyangiitis (MPA) is a small-vessel necrotizing vasculitis, commonly associated with myeloperoxidase-ANCA (MPO-ANCA) positivity. It typically presents with glomerulonephritis and pulmonary capillaritis, but does not involve granulomatous inflammation, distinguishing it from GPA.Incidence: ~3–24 cases per million annually; more common in middle-aged adults and slightly more frequent in males. 1 Aetiology and Risk Factors Aetiology […]

Overview EGPA (formerly Churg-Strauss syndrome) is a rare, small-to-medium vessel necrotizing vasculitis characterized by asthma, eosinophilia, and extravascular granulomas. It commonly affects the lungs, skin, peripheral nerves, and heart. Annual incidence: ~1–3 per million; peak onset in 40s–60s; no significant gender bias. Strongly associated with MPO-ANCA positivity in ~40–60% of patients; others are ANCA-negative. Physiology […]

Overview Immunoglobulin A vasculitis (IgAV), also known as Henoch–Schönlein purpura, is the most common primary vasculitis in children (peak incidence 4–7 years), with seasonal peaks after upper respiratory tract infections. It is defined as a small-vessel vasculitis with IgA1-dominant immune deposits affecting capillaries, venules, and arterioles, underscoring the central role of IgA in its pathogenesis. […]

Overview Granulomatosis with polyangiitis (formerly Wegener’s granulomatosis) is a rare, chronic, systemic necrotising vasculitis affecting small-to-medium-sized vessels, characterised by granulomatous inflammation, necrotising vasculitis, and tissue destruction, primarily involving the upper and lower respiratory tracts and kidneys. It falls under the ANCA-associated vasculitides (AAV). Peak incidence is in the 5th–6th decade, with slight male predominance and […]

Overview Felty syndrome is a rare but serious extra-articular manifestation of long-standing, seropositive rheumatoid arthritis (RA), characterized by the classic triad of RA, splenomegaly, and neutropenia. It was first described in 1924 by the US-American physician Augustus Roi Felty. It most commonly occurs after at least 10 years of poorly controlled RA and is associated […]

Overview Osteomalacia (adults) and rickets (children) are disorders of impaired bone mineralisation leading to soft, poorly mineralised bone. It arises when there is insufficient calcium–phosphate supply to the mineralising matrix due to vitamin D deficiency, calcium deficiency, phosphate deficiency (often FGF23-mediated). Nutritional rickets still occurs worldwide, while hypophosphataemic forms (e.g., XLH, tumour-induced osteomalacia) are rarer […]

Overview Knee osteoarthritis is a chronic, whole-joint disorder characterized by pain, stiffness, functional limitation and progressive structural change affecting cartilage, subchondral bone, synovium, menisci, ligaments and peri-articular muscles. Prevalence rises with age and obesity and contributes substantially to global disability; recent GBD analyses and reviews highlight knee OA as a leading cause of pain and […]

Overview Hypermobility Spectrum Disorder (HSD) describes symptomatic joint hypermobility with musculoskeletal (and sometimes systemic) consequences in people who do not meet the 2017 diagnostic criteria for hypermobile Ehlers–Danlos syndrome (hEDS) or another heritable connective-tissue disorder (HCTD). Prevalence of generalised joint hypermobility varies (≈2–35% depending on age/sex/ethnicity and cut-offs), with symptomatic states more common in females […]

Overview Goodpasture syndrome, now more precisely termed anti-glomerular basement membrane (anti-GBM) disease, is a rare autoimmune small-vessel vasculitis affecting lungs and kidneys, typically manifesting with diffuse alveolar hemorrhage and rapidly progressive glomerulonephritis.  Microscopic polyangiitis (MPA) has an estimated incidence of approximately 0.5 to 1.8 cases per million per year. It demonstrates a bimodal age distribution, […]

Overview CRPS is a disproportionate, regional pain syndrome of a limb that typically follows injury or surgery and features sensory, vasomotor, sudomotor/oedema, and motor/trophic changes. The prevalence after limb fracture/surgery varies widely (≈1–7% overall, higher in some distal radius cohorts) and early recognition with rehabilitation improves outcome. Important risk factors include fracture (especially wrist/ankle), immobilisation, […]

Overview Chronic widespread pain (CWP) is a nociplastic pain phenotype defined by persistent (≥3 months) pain affecting multiple body regions, with high comorbidity with fatigue, sleep disturbance, mood symptoms and functional impairment. The pooled global prevalence is ~10% (women>men), with higher rates in lower-HDI settings. CWP is recognised in ICD-11 within the chronic primary pain […]

Overview Caplan syndrome, also known as rheumatoid pneumoconiosis, is a rare condition seen in patients with rheumatoid arthritis (RA) who have had occupational exposure to inhaled dust, particularly coal dust or silica. It is characterised by multiple, rounded pulmonary nodules and underlying pneumoconiosis. It primarily affects middle-aged male coal workers and is now rare in […]

Overview Hydroxyapatite Deposition Disease (HADD) is a crystal-induced tendinopathy caused by the deposition of hydroxyapatite (HA) crystals, typically in periarticular soft tissues, especially tendons and bursae. The shoulder (supraspinatus tendon) is most commonly affected. It often presents between ages 30–60, more frequently in women. While often asymptomatic, it can cause acute pain and functional limitation […]

Overview Pseudogout, more accurately known as calcium pyrophosphate deposition disease (CPPD), is a crystal arthropathy characterized by the deposition of calcium pyrophosphate dihydrate crystals in articular cartilage and soft tissues, leading to joint inflammation. It most commonly affects elderly individuals, especially over the age of 60, with a slight female predominance. Clinically, it often mimics […]

Overview UCTD is a systemic autoimmune disease with features of connective tissue disease (CTD), but does not fulfill classification criteria for any specific CTD such as SLE, Sjögren’s syndrome, systemic sclerosis, or polymyositis. It is a diagnosis of exclusion used for patients with persistent autoimmune features who do not evolve into a defined CTD. Commonly […]

Overview Takayasu arteritis is a rare, chronic large-vessel vasculitis primarily affecting the aorta and its major branches, leading to stenosis, occlusion, or aneurysm formation. It most commonly affects young women (<40 years), particularly of Asian descent. The global incidence is estimated at 1–2 per million per year, with a female predominance (F:M ~9:1). It is […]

Overview Sjögren’s Syndrome is a chronic, systemic autoimmune disorder characterized by lymphocytic infiltration and destruction of exocrine glands, primarily affecting the salivary and lacrimal glands, leading to dry mouth (xerostomia) and dry eyes (keratoconjunctivitis sicca). It commonly affects middle-aged women, with a female:male ratio of approximately 9:1. It can be primary (isolated) or secondary (associated […]

Overview Reactive arthritis is a seronegative spondyloarthropathy that occurs after a genitourinary or gastrointestinal infection, typically presenting as an asymmetric oligoarthritis, often with associated conjunctivitis and urethritis (formerly Reiter’s syndrome). It most commonly affects young adults aged 20–40 and shows a strong association with HLA-B27. Incidence is estimated at 30–40 per 100,000, with higher rates […]