My son has been around his cousin who I just found out had MRSA on the bottom of his foot. He also had a red line going from his foot to his groin. His father called me to tell me that he had a sore on his thumb from riding his dirt bike and now complaining his entire arm hurts and has a red line from his hand to his armpit.
He has developed a complication called lymphangitis due to the infection. As this is MRSA infection he needs to be treated with appropriate antibiotics as per the sensitivity pattern.  Hope this answers your questions.  All the best