Op not sure if anyone answered your question on lymphedema.
There are 2 types, primary and secondary. Primary is hereditary and can come on at any time or never. Secondary can be caused by Injury to limb or due to have lymph nodes removed (ie. Cancer treatment).
It's basically where the lymphatic system breaks and stops working, the lymphatic system is what drives or is the immune system, so the fluid stops moving and collects hence the swollen limbs. which is why people with lymphedema who get an injury on their affected limb are at high risk of cellulitis because the immune system isn't working to make them better.
At first look I thought lymphedema, and I think others have said, it's not widely known or dealt with properly or quickly, some NHS trusts don't have lymphedema teams and it's basically ignored and it's not an area that's studied.
Its not overly life threatening apart from the infection, but its uncomfortable and inconvenient.
Mine is much worse if I have been on my feet, sat in a chair, kneeling or in the heat.
I hope he gets whatever treatment he needs and I am surprised he wasn't given antibiotics and treat the infection at the minimum