<human>: My three year old son has a rash on his elbows, lower back and on his buttocks, front and back of his legs. He has complained of leg pain in one leg and it s been around his calf muscle. There has been no fever and his diet and sleep habits have been normal.
<bot>: An image of the rash is very helpful in diagnosis, but putting all your description together : rash on lower back, lower limbs and arthralgia urge me to ask: is this skin rash palpable ? Can you feel it ? If put your fingers around a spot and move your fingers from each other, does it blanch or go away ? Any previous cold or a runny nose in the past 2 weeks? If this rash doesn't blanch, and you can feel it, if it was associated with abdominal pain then there is a chance that your child has HSP (Enoch schooling purpura) and you should refer him to his pediatrician to order some tests. I hope this helps