After reading this chapter you should be able to assess, diagnose and manage:
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acute and chronic musculoskeletal disease
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musculoskeletal inflammatory diseases
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common vasculitic disorders
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common inherited bone disorders
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developmental bone disorders—scoliosis, hip dysplasia, Perthes disease
Musculoskeletal symptoms , particularly pain, are common in children and usually relate to injury, overuse, rapid growth, biomechanical or postural abnormalities. Musculoskeletal disorders are less common and they are usually rheumatological or orthopaedic in origin.
Acute and chronic arthritis
Arthritis is the inflammation of joints and usually presents with pain, swelling, erythema and a reduction in the movement of the affected joints. Children who present acutely need prompt diagnosis and management, especially if an infective cause is suspected.
Causes and associations of arthritis include:
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infection
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bacterial— Staphylococcus aureus, Group A beta-haemolytic streptococcus, Streptococcus pneumoniae, rarely TB
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viral—mumps, rubella, parvovirus, adenovirus, coxsackie B
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other organisms—mycoplasma, Borrelia burgdorferi, rickettsia
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juvenile idiopathic arthritis
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connective tissue disorders—SLE, dermatomyositis, polyarteritis nodosa (PAN)
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vasculitides—Henoch-Schönlein purpura, Kawasaki disease
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inflammatory bowel disease
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haematological—haemophilia, sickle cell disease, leukaemia
Septic arthritis
Septic arthritis is a significant infection of the joints especially in children under 2 years of age. It usually involves a single joint and the infection is commonly acquired via haematological spread rather than local injury. The most common bacterial organism is Staphylococcus aureus , followed by Streptococcus.
Localised symptoms such as pain, restricted movement, swelling and redness are common presenting features and children are usually systemically unwell with pyrexia and elevated inflammatory markers. In young infants, there may be pain on moving the limb and therefore the limb is kept in a neutral position when at rest. Infants with hip involvement hold their legs flexed, externally rotated and abducted whilst older children may limp while walking or even refuse to weight bear due to pain.
Suspected septic arthritis requires an urgent orthopaedic opinion as joint aspiration can provide key information informing diagnosis and choice of antimicrobial therapy.
Investigations
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full blood count—elevated white cell and platelet counts
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ESR and CRP—usually raised
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blood culture—to identify organism and ensure appropriate antibiotic treatment
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joint aspiration—for culture
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joint USS—to identify any effusion
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x-ray—initially normal but established disease results in increased joint space and soft tissue swelling
Management and treatment
Antibiotic treatment must be commenced promptly following blood cultures and joint aspiration. It is reasonable to start flucloxacillin and cefotaxime in children below 2 years and flucloxacillin and ampicillin in older children. Antibiotic regimes, however, should be discussed with local microbiologists and schedules tailored in response to the results of cultures and sensitivities. The duration of antibiotics is usually between 4 and 6 weeks.
Reactive arthritis
Reactive arthritis a term used to describe joint pain and swelling triggered by an infection in another part of the body. It usually presents within 6 weeks of the initial infection and often involves the knee or ankle joints. Reactive arthritis commonly follows infection such as salmonella, shigella or campylobacter gut infections. Sexually transmitted infections such as chlamydia must be considered in the differential diagnosis.
Reactive arthritis can be associated with an acute anterior uveitis or urinary tract inflammation. Although any individual can present with an episode of reactive arthritis, it occurs more commonly in individuals who are HLA B27 positive.
Common presenting features will include transient joint swelling, pain and restriction of movement. The joints of the lower limbs, particularly the hip, are often involved although the interphalangeal joints can also be affected.
Treatment and management
Acute inflammation is usually treated with nonsteroidal antiinflammatory drugs such as ibuprofen, naproxen or diclofenac. Rarely, reactive arthritis can become chronic and children may require intraarticular corticosteroid injection or systemic immunosuppressive medication such as methotrexate.
Juvenile idiopathic arthritis (JIA)
JIA is an umbrella term for a heterogeneous group of chronic inflammatory arthritides with onset before the age of 16 years and lasting for at least 6 weeks. The cause of the condition is unknown although a combination of genetic and environmental factors is likely. It is a diagnosis of exclusion but is the most common cause of chronic joint disease in children. Children and young people where this diagnosis is suspected should be referred to paediatric rheumatology services for review and confirmation.
JIA includes seven disease subtypes with each having markedly different characteristics. There is also clinical heterogeneity within each of the JIA subtypes that reflects a probable variability in disease pathogenesis. Girls are more commonly affected than boys and there are two peak ages of onset at 1–3 years and 8–9 years ( Table 29.1 ).
| JIA subtype | Joints involved |
|---|---|
| oligoarticular JIA | 1–4 |
| systemic onset JIA | 1 or more |
| polyarticular (RF-negative) JIA | 5 or more |
| polyarticular (RF-positive) JIA | 5 or more |
| psoriatic JIA | multiple |
| enthesitis ∗ -related JIA | multiple |
| undifferentiated JIA | multiple |
Investigations
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full blood count—normochromic, normocytic anaemia with occasional haemolysis Platelets and white cells are usually elevated, although thrombocytopaenia may occur
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blood film at diagnosis—to rule out malignancies
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ESR and CRP—usually raised at presentation and suggest a more severe disease course
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antinuclear antibodies (ANA)—seen in oligoarthritis and are risk factor for uveitis
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Rheumatoid factor (RF) and anti-CCP antibodies (anticyclic citrullinated peptide) are both autoantibodies found in JIA
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HLA B27 positivity—common in enthesitis-related and psoriatic arthritis
Treatment and management
Children with JIA should be managed by a paediatric rheumatology multidisciplinary team with the aim of achieving complete disease control.
Adequate control of pain is crucial to the initial management plan and NSAIDs are usually prescribed. Corticosteroids will modify the disease process and contribute to the analgesic effect but with recognised side effects. Consequently, other disease-modifying medications are used to reduce exposure to corticosteroids. They are commenced soon after diagnosis in children with polyarthritis and later in the disease course in those with oligoarthritis that is unresponsive to joint injections. Methotrexate would usually be the first-choice disease-modifying medication and is usually administered subcutaneously in children. There are a wider range of newer biologic medications that can be used in children whose disease does not respond completely to methotrexate.
Oligoarticular JIA
Oligoarthritis is the most common subtype of JIA, and although it can present at any age, it is most commonly seen in girls in the 1- to 3-year age group. Less than four joints are involved, but these may not be painful and so presentation may be late in the disease course. Parents often notice swelling and limping rather than the child complaining of pain. Uveitis is common, particularly in preschool girls with a positive ANA and is usually asymptomatic, so early and regular slit lamp examinations are essential.
Treatment and management
Synovitis is initially managed with NSAIDs and intraarticular corticosteroid injections. If children require frequent injections or develop features suggestive of joint damage, then they will need systemic immunosuppression with drugs such as methotrexate.
Systemic onset JIA
Systemic onset JIA is a rare autoinflammatory disease. Children are often unwell at presentation and may need extensive investigations to exclude sepsis or malignancy. The condition is characterised by:
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recurrent daily fevers that spike in the morning and early evening
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salmon-pink urticarial rash
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polyarthritis affecting the knees, wrists and ankles is very common
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lymphadenopathy, splenomegaly and hepatomegaly
Uveitis is rarely associated with systemic onset JIA.
Polyarticular JIA
Polyarthritis affecting more than four joints is uncommon, and the majority of children have a negative rheumatoid factor test. Presentation can occur at any age and joint involvement may involve the cervical spine, temporomandibular and hands ( Figure 29.1 ). Axial, large joint involvement is more common in children who are HLA B27 positive. IgM rheumatoid factor positive disease is rare and usually occurs in adolescent girls who present with a symmetrical, small joint polyarthritis that behaves in a similar way to rheumatoid arthritis.
