What causes high ALT and serum ferritin along with digestive issues in a 21-year-old male?

Hello doctor,

My 21-year-old son has elevated ALT (125 U/L) and elevated serum ferritin (665 micrograms/L). These levels may be higher now, as they were elevated but significantly lower three months ago. He also has slightly elevated creatinine and albumin. His urine is clear, but I am advised that his kidney function, although within acceptable limits, is poor for his age. He has looked and felt off-color for almost six months now. Sometimes grey and sometimes yellow, although his bilirubin and GGT are expected, and his eyes are not yellow.

He suffers from intermittent nausea, bloating, belching, and appetite loss, and his tummy looks swollen. He does not have hemochromatosis because his transferrin saturation is fine. He is tall and very lean. Blood tests, urine tests, and an ultrasound of the liver, kidneys, and abdomen are all clear. Anti-mitochondrial antibodies are negative. Anti-LKM antibodies, anti-smooth muscle antibodies, and anti-parietal cell antibodies are negative. C-reactive protein is fine, and I have been told he does not have hepatitis A, B, or C. I am very anxious to obtain a diagnosis for him, as he no longer leaves the house due to his symptoms, and I am worried that whatever it is that he has is progressing.

Please help.

Thank you.