AG in MM

Q: An anion gap (AG) in multiple myloma (MM) will be? - select one

A) high

B) low

Answer: B

Patients suspected of MM, typically with CRAB, i.e., hypercalcemia, renal insufficiency, anemia, and bone disease, would probably have a low anion gap. 

The two contributing factors to low AG are:

• Severe hypercalcemia acts as an unmeasured cation 
• A cationic IgG molecule

# electrolytes

#acid-base

References:

1. Mansoor S, Siddiqui I, Adil S, Nabi Kakepoto G, Fatmi Z, Ghani F. Anion gap among patients of multiple myeloma and normal individuals. Clin Biochem. 2007 Feb;40(3-4):226-9. doi: 10.1016/j.clinbiochem.2006.10.011. Epub 2006 Nov 1. PMID: 17156769.

2. Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol 2007; 2:162.

3. De Troyer A, Stolarczyk A, De Beyl DZ, Stryckmans P. Value of anion-gap determination in multiple myeloma. N Engl J Med 1977; 296:858.