Fatigue & Weakness
A 6 year old boy is referred with a 7 month history of gradual tiredness and weakness. He had complained of leg pains after exercise which his mother thought were growing pains. However in the last 2 weeks he had become unable to climb the stairs without help and was coming down the stairs on his bottom. He was waking sometimes at night with leg pains. For several months he had been more prone to ‘sunburn’ with a rash across his face.
He was otherwise well but was struggling in the sports at school - the teacher had made comment to his mother that he had to sit out of games after a short while. His school work was fine but the teacher made comment that John was more withdrawn and seemed tired at school.
There was no family history of note. He walked at 14 months and there were no concerns about his development.
On examination, he looked well but clearly was walking slowly and had difficulty taking off his T shirt. He was slow to get up off the chair and get on and off the examination couch. pGALS showed that he had restriction of both wrists, elbows and walked with his knees slightly flexed. There was no joint swelling but he was uncomfortable moving his limbs and was noted to be slow to raise his arms and move his limbs in general. A rash over his cheeks was noted and he had some scaly patches over both knees.
What is the diagnosis?
The diagnosis is Juvenile Dermatomyositis (JDM)
This is likely JDM rather than an inherited myopathy as there is regression rather than delay in motor milestones. The rash is also suggestive of JDM but a malar rash can also occur in JSLE. Inflammatory joint disease (Juvenile Idiopathic Arthritis) can be indolent but would not explain the rash. There are some red flags (systemic upset and night waking), and so malignancy has to be excluded (e.g., leukaemia).
The diagnosis of JDM is confirmed by the clinical presentation, blood tests (raised muscle enzyme (e.g., creatine kinase)), and imaging (MRI of his thigh muscles showed inflammatory changes). Nail fold capillaroscopy showed dilated blood vessels consistent with JDM. If the blood tests or MRI are inconclusive, then muscle biopsy may be needed.
Urgent referral to hospital may be required if there is any difficulty with swallowing or concern of aspiration risk due to laryngopharyngeal weakness.
The photograph below shows Gottren's papules consistent with JDM