Musculoskeletal features are common in multisystem disease - this can be true arthritis (usually affecting many joints in a symmetrical pattern) or arthralgia (painful joints without overt swelling) with or without myalgia (muscle pain) or myositis (muscle pain and tenderness, often with weakness).
Systemic features may be present - malaise, fatigue, weight loss, fever, rash - and may relate to conditions such as connective tissue disease, for instance Juvenile Systemic Lupus Erythematosus, Juvenile Dermatomyositis, Vasculitis, Scleroderma, Periodic (Autoinflammatory) syndromes, although the differential diagnosis includes serious conditions such as infection and malignancy.
There is also the possibility of chronic diseases that may develop musculoskeletal features and these include inflammatory bowel disease, metabolic conditions and genetic syndromes.
Diagnosis rests on clinical assessment and careful use and interpretation of investigations.
The photograph below shows skin vasculitis
The photograph below shows severe ischaemic changes in a child with vasculitis - several toes were lost due to gangrene