Case of Hyperammonemia & Fanconi’s Syndrome

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Quick case summary as presented in Renal Grand Rounds today:  A 54 year-old man presents with altered mental status, a sky-high ammonia level (>200) and anemia requiring blood transfusion.  Other unusual lab values include hypophosphatemia and hypokalemia with a significant non-anion gap metabolic acidosis.  Subsequent workup reveals 3+ glucosuria and aminoaciduria.  What’s the underlying diagnosis?

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.  

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