Paediatrics: Juvenile idiopathic arthritis

Juvenile idiopathic arthritis

JIA is a common chronic childhood disorder (UK prevalence 1/1000; inci-dence: 1/10 000). It is a diagnosis of exclusion in children <16yrs old with a history of at least 6wks of persistent arthritis. JIA is divided into 7 subsets for research purposes.¹ These are not diagnostic categories, but are useful clinical groups. As a child’s symptoms evolve with time (e.g. the appear-ance of a psoriatic rash), they may change subtype.

Classification of JIA¹

•   Systemic arthritis: relative frequency,10–13%.

•   Oligoarthritis (persistent or extended): relative frequency, 40%.

•   Polyarthritis (rheumatoid factor +ve): relative frequency, 3%.

•   Polyarthritis (rheumatoid factor –ve): relative frequency, 27%.

•   Psoriatic arthritis: relative frequency, 2–15%.

•   Enthesitis-related arthritis: relative frequency, 1–7%.

•   Undifferentiated arthritis: relative frequency, 2–15%.

Differential diagnoses of childhood arthritis

•   Infection:

•   bacterial—septic arthritis; osteomyelitis

•   viral—rubella; parvovirus B19; infectious mononucleosis;

•   Lyme, Brucella, TB.

•   Post-infection:

•   reactive arthritis;

•   post-streptococcal reactive arthritis;

•   rheumatic fever.

•   Malignancy:

•   leukaemia;

•   neuroblastoma;

•   p bone tumours—benign or malignant;

•   metastatic disease.

Orthopaedic:

•   Perthes and other osteochondritides;

•   slipped upper femoral epiphysis;

•   hip dysplasia;

•   infantile coxa vara;

•   chondromalacia patellae;

•   irritable hip.

•   Hypermobility:

•   benign hypermobility—local or generalized;

•   Marfans, Ehlers–Danlos;

IBD.

·Connective tissue disease:

•   SLE;

•   juvenile dermatomyositis;

•   systemic sclerosis—limited or progressive.

• Metabolic disorders:

•   gout;

•   mucopolysaccharidoses.

• Haematological:

•   SCD;

•   other haemoglobinopathies;

•   haemophilia.

• Vasculitis:

•   HSP;

•   polyarteritis/microscopic polyangitis

•   Kawasaki disease;

•   Takayasu arteritis.

• Immunodeficiency syndromes.

• Other inflammatory disorders:

•   sarcoid;

•   chronic recurrent multifocal osteomyelitis;

•   SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis).

• Idiopathic pain syndromes:

•   chronic regional pain syndromes;

•   fibromyalgia

‘non-organic pain’—a cry for help.