ABP Pediatric Rheumatology key terms

A multiprotein assembly inside innate immune cells that activates caspase-1 and releases mature interleukin-1 beta. Gain-of-function variants in its components cause cryopyrin-associated periodic syndromes and contribute to familial Mediterranean fever.

A major histocompatibility class I allele strongly associated with enthesitis-related arthritis and axial spondyloarthritis. Carriage raises suspicion but is common in healthy people, so it supports rather than establishes a diagnosis.

A test detecting autoantibodies that bind components of the cell nucleus. Low titers are frequent in healthy children, so a positive result supports but never confirms lupus or another connective tissue disease.

Antibodies directed against double-stranded DNA. They are relatively specific for systemic lupus erythematosus, and their level often rises before or during flares, particularly lupus kidney disease.

Serum proteins consumed when immune complexes activate the classical pathway. Levels fall during active lupus, so serial measurement alongside anti-dsDNA antibody helps judge disease activity and response to treatment.

Antibodies against neutrophil granule proteins, reported as cytoplasmic (anti-proteinase 3) or perinuclear (anti-myeloperoxidase). They support a diagnosis of small-vessel vasculitis but can be falsely positive in infection and inflammatory bowel disease.

Ophthalmologic examination using a microscope and slit beam that reveals cells and flare in the anterior chamber. It is the standard method for screening and following chronic uveitis in children with juvenile idiopathic arthritis.

Needle aspiration of synovial fluid for cell count, Gram stain, crystal examination and culture. It is the definitive way to separate septic from inflammatory arthritis and can relieve a tense effusion.

An iron-storage protein measured in serum. Extreme elevation, especially with falling platelets and fibrinogen, suggests macrophage activation syndrome or hemophagocytic lymphohistiocytosis and should trigger urgent evaluation.

Chronic arthritis of unknown cause beginning before the sixteenth birthday and lasting at least six weeks, divided into subtypes including oligoarticular, polyarticular, systemic, enthesitis-related and psoriatic forms.

Arthritis of four or fewer joints during the first six months, typically knees or ankles in young girls, carrying a high risk of silent chronic uveitis that requires scheduled slit-lamp screening.

Subtype with spiking fever, evanescent rash, arthritis, lymphadenopathy and serositis. It is autoinflammatory rather than autoimmune, driven by interleukin-1 and interleukin-6, and may be complicated by macrophage activation syndrome.

A JIA category in which inflammation arises where tendons and ligaments insert into bone, often with sacroiliac or spinal involvement in HLA-B27 positive older boys; it resembles adult spondyloarthritis.

Inflammation of the uveal tract that in JIA is usually painless and invisible to parents, so scheduled slit-lamp examinations are essential because untreated disease causes synechiae, glaucoma and permanent visual loss.

A life-threatening hyperinflammatory state, mostly seen in systemic JIA, with persistent fever, falling blood counts, high ferritin, liver enzyme elevation and coagulopathy from uncontrolled macrophage and T-cell activation; urgent immunosuppression is required.

Childhood inflammatory myopathy producing proximal muscle weakness, heliotrope eyelid rash, Gottron papules and nailfold capillary changes; vasculopathy may cause skin ulceration, calcinosis, gut involvement or lipodystrophy.

Deposits of calcium salts in skin and subcutaneous tissue, a late complication of juvenile dermatomyositis and localized scleroderma that may cause pain, ulceration, infection and joint contracture.

In children, scleroderma most often takes a localized form: morphea plaques or linear bands of thickened skin that can tether a limb or the face and disturb growth, without internal organ fibrosis.

Episodic vasospasm of digital arteries triggered by cold or emotion, producing pallor, cyanosis, numbness and pain. In children it is often primary but may herald connective tissue disease when capillaries or autoantibodies are abnormal.

An overlap syndrome combining features of lupus, myositis and scleroderma with high-titer anti-U1 ribonucleoprotein antibodies; children may develop pulmonary hypertension and therefore need long-term surveillance.

Antibodies against phospholipid-binding proteins, including anticardiolipin, anti-beta-2-glycoprotein I and the lupus anticoagulant. Persistently positive results together with thrombosis define antiphospholipid syndrome.

Multisystem autoimmune disease in which autoantibodies and immune complexes injure skin, joints, kidneys, blood cells and the nervous system; children often have more severe renal and hematologic involvement than adults.

The most common childhood small-vessel vasculitis, with palpable purpura on dependent skin, abdominal pain, arthralgia and IgA-mediated glomerulonephritis; urine monitoring is required for months after apparent recovery.

Acute medium-vessel vasculitis of young children with fever, conjunctivitis, mucosal changes, rash, extremity swelling and cervical adenitis; coronary artery aneurysms are the feared complication, so intravenous immunoglobulin is given promptly.

Granulomatous large-vessel arteritis of the aorta and its branches that in children causes hypertension, absent pulses, claudication and systemic inflammation; vascular imaging is central to diagnosis and follow-up.

Recurrent syndrome of early childhood with regular febrile episodes lasting a few days, accompanied by aphthous ulcers, pharyngitis or cervical adenitis, with normal growth and health between attacks; it usually remits by adolescence.

Autosomal recessive autoinflammatory disease caused by MEFV variants, with short recurrent attacks of fever, abdominal or chest pain and arthritis; untreated inflammation can cause amyloidosis, and daily colchicine prevents attacks.

A spectrum of autoinflammatory disorders from gain-of-function NLRP3 variants, ranging from cold-triggered urticaria to neonatal multisystem inflammation with hearing loss and amyloidosis; interleukin-1 blockade is dramatically effective.

Regional or widespread musculoskeletal pain in children without inflammation, often triggered by injury or stress and maintained by central sensitization; examination is inconsistent with anatomy, and intensive physical and psychological rehabilitation is the treatment.

Sterile inflammatory bone disease of children with insidious pain, often in metaphyses, clavicles or vertebrae, and no infection; imaging shows edema and sclerosis, and nonsteroidal anti-inflammatory drugs or bisphosphonates are used.

Bacterial joint infection with acute monoarthritis, fever and refusal to bear weight; the joint must be aspirated urgently because untreated infection destroys cartilage within days and closely mimics juvenile idiopathic arthritis.

Chronic monoarthritis or oligoarthritis, usually of the knee, caused by Borrelia burgdorferi after tick exposure; serology confirms it and antibiotics cure it, so it must be excluded before diagnosing juvenile idiopathic arthritis.

Some inborn errors of immunity, such as common variable immunodeficiency or chronic granulomatous disease, present with arthritis, recurrent fever or granulomatous lesions; repeated or unusual infections should prompt immune evaluation.

An antifolate disease-modifying drug used first-line for polyarticular juvenile idiopathic arthritis and also in uveitis and dermatomyositis; blood counts, liver enzymes and renal function need periodic monitoring, and folic acid reduces side effects.

Biologics that neutralize tumor necrosis factor, used for polyarticular and enthesitis-related arthritis and for uveitis; screening for tuberculosis and hepatitis and vigilance for infection are required before and during treatment.

A recombinant interleukin-1 receptor antagonist given by daily injection, highly effective in systemic juvenile idiopathic arthritis, cryopyrin-associated periodic syndromes and macrophage activation syndrome; injection-site reactions are the commonest adverse effect.

Pooled human immunoglobulin given intravenously for immunomodulation, notably in Kawasaki disease to prevent coronary aneurysms and occasionally in autoimmune cytopenias or myositis; infusion reactions and rare thrombotic events occur.

Systemic steroids cause growth suppression, weight gain, hypertension, hyperglycemia, osteoporosis, cataract, striae and adrenal suppression, so the lowest effective dose with a planned taper and monitoring is used.

A parent- or child-completed questionnaire measuring physical function and discomfort in pediatric rheumatic disease; it is one of the core outcome variables used to judge response in juvenile idiopathic arthritis.

A structured process transferring adolescents with chronic rheumatic disease from pediatric to adult services, teaching self-management and vocational planning, and preventing loss to follow-up and disease flares.