A four-year-old child presents with mild fever, malaise, purpura, arthritis, abdominal pain and microscopic hematuria. What would be the most likely diagnosis

Henoch-Schönlein purpura affects the small blood vessels of the skin, joints, intestines and kidneys. It's most common before the age of seven but can affect anyone. Symptoms include reddish-purple spots on the lower extremities, swollen and sore joints, abdominal pain or bloody urine. The condition is often treated with steroids