Fever Rash and Pain
William is an 11 ½ year old boy of Pacific descent living in New Zealand who presents acutely to the Paediatric assessment unit with fever, a rash on his legs, and a swollen sore foot. The onset of symptoms followed a sore throat 1 week prior with a positive throat swab for Group A Streptococcus for which he had been prescribed Amoxicillin. He looked well and vital signs included temperature 39.3o C and heart rate 125/minute.
Examination revealed a grade 3/6 pan-systolic murmur, loudest at the left lower sternal border. There were no signs of heart failure or organomegaly. He had a non-itchy, macular, serpiginous rash with erythematous border on his lower limbs. His left ankle was warm, swollen and tender, limiting movement. Also of note he was obese with a BMI of 35.
He was admitted to the childrens ward for further investigation. His bloods showed an ESR of 58 and CRP of 79. ECG was normal other than a tachycardia (117/min) and PR interval of 0.16 sec (prolonged for heart rate and age). His chest X-ray was normal. Streptococcal serology was positive with ASOT of 1384 and anti-DnaseB of 640.
He was commenced on oral Penicillin and bed rest and an Echocardiogram was done. The Echocardiogram revealed moderate mitral regurgitation and aortic incompetence. He had ongoing fever, tachycardia and developed chest pain and breathlessness, especially lying down. A subsequent chest x-ray was consistent with new cardiomegaly. He was commenced on diuretics.
What red flags appear in the history at the initial presentation?
Fever, rash and swollen foot along with recent positive throat swab for Group A Streptococcus in a child of Pacific descent.
What are the red flags on observation/examination?
Tachycardia, serpiginous rash, very tender arthritis of left ankle and presence of a murmur (especially if new murmur).
What might have been the working diagnosis at the initial presentation of fever, rash and swollen foot with a positive throat swab?
Acute Rheumatic Fever. There may not always be an accompanying history of sore throat, let alone a positive throat swab. Have a high index of suspicion if the child is of Maori or Pacific Island descent and/or lives in an overcrowded situation, and presents acutely with joint pain with or without swelling, and with or without fever or rash. Check inflammatory markers and Streptococcal serology. Assess for new murmurs and perform an ECG. An Echocardiogram will be required if there is evidence of recent Streptococcal infection. The New Zealand guidelines for Rheumatic fever and streptococcal throat infections should be followed in high risk populations and a diagnosis of post-streptococcal reactive arthritis in these populations should not be made without consultation with General Paediatrics or Infectious Diseases.
Are there ongoing concerning features?
Continuing to spike temperatures with persistent tachycardia and development of chest symptoms consistent with heart failure; despite complete bed rest.
On history alone, what appears on your list of differential diagnoses?
In the absence of evidence for streptococcal infection septic arthritis and other reactive arthritides should be considered (Mycoplasma, Viral, Salmonella, Shigella, Campylobacter and Yersinia),
Other possibilities include Juvenile Idiopathic Arthritis (especially systemic onset), Kawasaki disease, Henoch Schönlein Purpura (if rash palpable purpura), Systemic Lupus Erythematosis, and Serum sickness.
How do the examination findings help to rationalise your differential?
The nature of the rash can be suggestive of likely pathology: for example a non-itchy, macular, serpiginous rash with erythematous border suggests Erythema marginatum seen in Rheumatic fever; palpable purpura especially on lower limbs and buttocks is seen in Henoch Schönlein purpura; a non-pruritic, macular, morbilliform or targetoid rash on trunk and extremities, often with a perineal confluence within the first few days, is suggestive of Kawasaki disease; a butterfly malar rash, with or without other rashes may suggest SLE.
The presence of a new murmur suggests carditis and needs a variety of bacterial, viral and mycoplasma agents investigated, along with tests for SLE (including ANA, dsDNA). Kawasaki disease should be considered if other clinical features suggest this (rash, non-purulent conjunctivitis, swelling of hands and feet, cervical lymphadenopathy, swollen cracked lips and strawberry tongue).
Echocardiograms done regularly, initially every 2 weeks, showed progression of Mitral Valve Regurgitation to severe Mitral Incompetence, along with thickened Mitral valve leaflets, suggesting acute recurrence on chronic (previously silent) Rheumatic Fever.
At 6 weeks into the illness and admission (and bed rest), a course of steroids (Prednisone) was started to settle persistently raised resting heart rate and inflammatory markers (ESR peak 101; CRP peak 211). He had a dramatic improvement with normalisation of heart rate and inflammatory markers, allowing relaxation of strict bed rest with gradual increase in mobilisation to allow discharge at 2 months on weaning Prednisone.
On withdrawal of the steroids he had a rebound increase in inflammatory markers accompanied by painful big toe metatarsophalangeal (MTP) joints bilaterally. He was readmitted for rest and the inflammatory markers settled without further steroids.
Subsequently there has been no evidence of progression of his Mitral and Aortic Incompetence, and no change in heart size. He has been advised about the importance of:
- Medical assessment for subsequent sore throats.
- Adhering to monthly prophylactic intramuscular injections of benzathine penicillin.
- Regular dental checks, and antibiotic prophylaxis for any dental procedures.
- Regular exercise and healthy diet for weight reduction.
Diagnosis - Acute on Chronic Rheumatic Fever.