89) A 61-year-old man is admitted because of altered mental status. On physical examination, he is afebrile. Laboratory studies show sodium 136 mmol/L, potassium 4.4 mmol/L, chloride 108 mmol/L, CO2 30 mmol/L, glucose 78 mg/dL, urea nitrogen 49 mg/dL, calcium 13.8gm%, creatinine 5 mg/dL, hemoglobin 8.9gm%, total protein 8.3 g/dL, albumin 3.7 g/dL, alkaline phosphatase 116 U/L, AST 45 U/L, ALT 22 U/L, and total bilirubin 1.2 mg/dL. The patient is started on aggressive Intravenos hydration. Which of the following may be typically seen with this patient’s disease?
A) Hypercellular Bone marrow with many blasts
B) Serum protein electrophoresis with polyclonal hypergammaglobulinemia
C) An increase in all immunoglobulins ( IgA, IgG and IgM)
D) A negative anion gap
E) Increased Alkaline Phosphatase
F) A positive bonescan
Archer USMLE Step 3 Blog 
B
b
Sounds like MM
D. negative anion gap
bbb
I think the answer is worded wrongly. Since there is high ALP and low AG, neither of them is the answer (unless the question ask to check all answers that apply). MM give MONOclonal gammopathy (IgG) and not polyclonal. BM biopsy is definitive and shows >10% plasma cells.
C
D, negative anion gap in multiple myeloma due to paraptoteinemia
D. MM proteins are cationic ( + charge ). In order to compensate for this increase, HCO3 – and Cl- ( Anions ) increase, producing a decrease in Anion Gap.
A low Albumin level does the same thing. For every 1 point decrease in Albumin, there is 2 point decrease in the Anion Gap.
Why increase calcium and renal failure ? Could it be hyperparathyroidism and bone scan could be the answer.
???
D
Multiple Myeloma is a cancer of plasma cells which over produce MONOCLONAL antibodies- it means that MM can produce IgG, IgM, or IgA but not all of them at one time. Most of the time, it produces IgG.
Symptoms of MM : “CRAB”
Calcium- HyperCalcemia- these antibodies (paraprotein)
activate osteoCLASTS which destroy bones
(Incr Ca) but not osteoBLAST- thus normal
Alk Phos and Normal bone scan (+ in Paget)
Renal failure- light chains (Bence Jones proteins)
deposit in kidneys causing failure (bun/Cr ratio
less then 20- intrinsic kidney failure)
Anemia- abnormal mostly MATURE plasma cells
accumulate in bone marrow where they interfere
with production of RBC (Anemia)
Bone fracture, back pain- osteoCLASTS destroy bones
causing pathological fracture & back pain.
The question is testing the association between MM and Anion Gap. MM & other monoclonal gammopathies over produce a monoclonal Ig (i.e IgG, IgM, or IgA).
Monoclonal Ab may behave as cations or anions and can chance the anion gap.
Most IgG are Cations- thus lowering the AG
Most IgA are Anions – thus Incr the AG
Since MM mostly produces IgG- we mostly associate MM as having a low AG. (Answer D.)
Conclusion-
A- is not correct bc bone marrow is filled with MATURE abn plasma cells not blasts
B- is not correct bc SPEP show Monoclonal Ig, not polyclonal
C- is not correct bc only one type of Ig is increased not all of them
E and F- are not correct bc MM has normal Alk Phos and Neg bone scan respectively.
Anion Gap and Monoclonal gammopathies
http://m.cjasn.asnjournals.org/content/6/12/2814.full#ref-16