Fever and Pain

Kevin is an 18-month old boy who presents to the paediatric day unit with a 4-week history of fevers and reluctance to weight-bear. The onset of symptoms coincided with a return from a family holiday to a resort in Turkey, where he had had a brief diarrhoeal illness, but had otherwise been well. His mother recalls him refusing to be put down on his feet and instead dropping onto his bottom when they returned home. He had come to the Emergency department, where his temperature was 38.5^oC. He had an x-ray of his hips, which was reported as normal, although difficulty in positioning was noted.

Kevin subsequently continued to spike temperatures of 38-39^oC that were only briefly relieved by paracetamol (acetaminophen) and ibuprofen, which he had been taking regularly throughout the illness. During this time his mobility varied between completely refusing to mobilise to cruising around furniture, and seemed to be transiently improved following paracetamol (acetaminophen) or ibuprofen. His mother reported that he had previously been very active and used to run without difficulty. She had noticed that he seemed to be in pain when she changed his nappy / diaper. In the week prior to admission he had been waking at night crying with pain.

Kevin's weight at 8.6kg was on the 2^nd centile. Examination revealed a small, miserable, uncomfortable child with a temperature of 39.2^oC. Heart rate was 160 beats per minute with a systolic murmur. His chest was clear, with no coryza. His abdomen was soft and non-tender, with a 1-2cm liver edge below the costal margin but no splenomegaly. He had inguinal and cervical lymphadenopathy. Ear, nose and throat examination was unremarkable. There was no bruising, erythema or petechiae on his skin. Joint examination showed no swelling, redness or increased temperature at any joint; range of passive movement was normal everywhere apart from the right hip, where internal rotation caused him to cry and wriggle away.

What red flags appear in the history at the initial presentation?

Fever, and refusal to weight bear.

What might have been the working diagnosis at the initial presentation of pain, fever and refusal to weight bear?

Septic arthritis:

It is important to note that x-rays can be normal at presentation.
Once septic arthritis is considered, discussion with orthopaedics and infectious diseases colleagues is mandatory to discuss the management plan.
There should be a low threshold for joint aspiration.

Are there ongoing concerning features?

Continuing to spike temperatures despite having variable mobility, length of time of symptoms, transient improvement with anti-inflammatory medications.

How might this case have been managed differently during the intervening 6 weeks?

An earlier referral to paediatric rheumatology or orthopaedics.

He could have had blood tests including inflammatory markers and autoantibodies, and imaging, (such as a hip ultrasound and/or MRI). Also, consider x-rays of knees as well as hips in a child with a limp (in case of referred pain).

What is your differential diagnoses based on the history?

Osteomyelitis, TB arthritis, Perthes disease, Juvenile Idiopathic Arthritis, Leukaemia, Primary Bone Tumour, Developmental Dysplasia of the Hip, and Transient Synovitis of the hip may all have been on the initial differential diagnosis.

How do the examination findings help to narrow your differential?

Look carefully for petechial rash, lymphadenopathy and hepatosplenomegaly which may suggest malignancy such as Leukaemia.

Restricted hip rotation in an otherwise well school aged child may be Perthes Disease.

Failure to thrive, night sweats or a history of a TB contact could suggest TB.

Joint swelling or restricted joint movement of other joints may suggest Juvenile Idiopathic Arthritis (isolated involvement of a hip joint is unusual).

In a well child, with normal examination and investigations, Transient Synovitis of the Hip is likely especially if there was a preceding history of an upper respiratory viral illness.

Fever and an unwell child are consistent with infection (septic arthritis, TB arthritis, acute rheumatic fever, or osteomyelitis) but may also occur in malignancy.

Progress

Kevin looked a little better and his temperature came down after a further dose of paracetamol (acetaminophen). Full blood count showed haemoglobin 75g/l, platelets 258 x10⁶, white cell count 10 x 10⁶/L; C-reactive protein 89 (normal <10mg/L). Hip ultrasound scan demonstrated a small effusion of the right hip and he was taken to operating theatre for a hip aspiration. Blood cultures were positive for staph aureus. Repeat x-ray of his hip showed erosion in the iliac bone on the right side, in keeping with osteomyelitis.

Diagnosis

Osteomyelitis

Fever and Pain

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