Hello @sueatt You sound absolutely frantic about your son and it’s understandable. He’s only 22 years old and in a fight for his life. I want to help find some answers for him and bring your stress level down to a manageable level for both your sakes.

Let me welcome you to Mayo Clinic Connect. We’re a community based forum of members who help each other through our shared experiences. We’re not doctors so we can’t diagnose or offer treatments. But most of us have had some significant health issues in our lives or are caregivers and loved ones of someone who has. So we’re very empathetic and do our best to help each other other out with finding answers, offering suggesting and providing encouragement and hope.

To find you the right group and conversations for your son, I’m going to ask some questions just for clarity. You posted your initial comments in this Covid 19 discussion on booster shots because your son is showing no antibodies after this J&J vaccine. But after reading both of your comments, I think this discussion is better suited to the Kidney & Bladder groups where there have been a few chats on FSGS and many regarding chronic kidney disease.
https://connect.mayoclinic.org/group/kidney-conditions/
Your son has been diagnosed with Chronic Kidney Disease (CKD) and focal segmental glomerulosclerosis (FSGS). Was this the result of your trip to the Mayo Clinic? Was this also where he was diagnosed with IgA deficiency? It is a rare disease which can result in autoimmune diseases and in this case it sounds like the target is your son’s kidneys.
As you mentioned he’s also now having to be super cautious to avoid any illnesses as his immunity is impaired. Is this all recent or has he been prone to illness for most of his life?

Was your son provided with a treatment plan and continued follow up care plan with a local primary care provider or kidney specialist? Is he on any medications? Is he working with a dietician to find the best food plan to protect his kidneys from further inflammation and damage besides being on the strict vegan diet?

What were his symptoms leading up to the discovery? You mentioned it was discovered in routine blood test.
Was he having any kidney issues before then? Has his CKD been staged to the severity of his disease?
Does he undergo dialysis treatments?

I found 1 clinical trial result but nothing ongoing at the current time. https://clinicaltrials.gov/ct2/show/NCT00024934?cond=IgA+Deficiency&cntry=US&draw=2&rank=1
https://www.mayoclinic.org/diseases-conditions/fsgs/symptoms-causes/syc-20354693
https://www.kidney.org/atoz/content/focal
https://rarediseases.info.nih.gov/diseases/10197/selective-iga-deficiency