This patient had multiple myeloma, as revealed by an M spike on serum protein electrophoresis. The diagnosis can explain all the major aspects of his presentation:
-myeloma is the cause of his anemia.
-myeloma is a cause of hyperammonemia (plasma cells for whatever reason have the ability to produce large amount of ammonia)
-myeloma and other paraproteinemias are a major cause of adult-onset Fanconi's Syndrome, which this patient has, as demonstrated by his aminoaciduria, glucosuria, phosphaturia, proximal renal tubular acidosis.