Name:
A 72-Year-Old with an Elevated Gamma Gap
Description:
A 72-Year-Old with an Elevated Gamma Gap
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Duration:
T00H05M03S
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Upload Date:
2022-02-28T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
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CATHY: Hi, welcome to Harrison's Podclass, where we discuss important concepts in internal medicine. I'm Cathy Handy.
CHARLIE: And I'm Charlie Wiener, and we're coming to you from the Johns Hopkins School of Medicine.
CATHY: Welcome to Episode 21: A 72-Year-Old with an Elevated Gamma Gap.
CHARLIE: Okay, here's the case. You are evaluating a 72-year-old man who's been diagnosed with the monoclonal gammopathy of undetermined significance, or MGUS, after finding an elevated gamma gap on routine blood testing.
CATHY: Let's pause there, and just go over a gamma gap to make sure that we're on the same page. First, the gamma gap, or paraprotein gap is the difference between the measured serum protein and the measured serum albumin. The presumption is that the major constituent of the serum protein is albumin, but any process that elevates the paraproteins will lead to a larger difference between the serum protein and the serum albumin. Typically, we expect that difference to be less than 4 g/dL, but elevations in the gamma gap can be seen in any of the paraproteinemias, and this includes multiple myeloma, other blood cell dyscrasias, or even viral infections such as HIV and hepatitis C.
CHARLIE: If you find a patient with an elevated gamma gap, how do you evaluate it?
CATHY: Well, the first step is to rule out some of the infections that I mentioned, but then you can also do a serum protein electrophoresis to identify what the non-albumin serum protein is, and really you're looking to see if it's monoclonal or polyclonal.
CHARLIE: So, this patient had an elevated gamma gap, and his protein electrophoresis was said to be consistent with an MGUS. What's an MGUS, Cathy?
CATHY: It's a plasma cell disorder that's a precursor to multiple myeloma. You need to distinguish it from multiple myeloma just to ensure that it's really of undetermined significance. So, the criteria that you're looking for are an M-spike that's measured as less than 3 g/dL. If you do a bone marrow biopsy, you want to see that there are fewer than 10% clonal plasma cells. There should be no evidence of other B cell proliferative disorders, and you shouldn't have any myeloma-related organ or tissue impairment, so no end-organ damage or no bone lesions.
CHARLIE: Okay. Let's go back to this patient. So, his M protein spike was measured at 1g/dL. His bone marrow biopsy demonstrated 5% clonal plasma cells and he has no evidence of end-organ bone damage. Sounds like he does have an MGUS then, right?
CATHY: Yup.
CHARLIE: Okay.
CHARLIE: He reports his appetite is excellent, and he has no weight gain or weight loss in the past one year. His past medical history is notable for mild hypertension, treated only with a diuretic, and hyperlipidemia treated with atorvastatin. He has no history of latent or active tuberculosis, and his HIV screen is negative. He still works as an international travel consultant, and walks at least two miles three times a week. His physical examination is totally unremarkable.
CHARLIE: Anything else you want to know?
CATHY: Well, we need to know a few more of the labs. So, specifically, the hemoglobin, the calcium, and the renal function, or the so-called CRAB criteria.
CHARLIE: Those are all normal on laboratory testing.
CATHY: Okay, so sounds like he definitely meets the criteria for MGUS, and it's really not that surprising, because MGUS is pretty common. It occurs in about 1% of the population older than age 50 years, and then in people who are older than 75, you can see it in up to 10% of individuals. But we do care about it, and we want to know if people have it if we find an elevated gamma gap because the risk of progression to multiple myeloma is about 1% per year.
CHARLIE: Okay, so let's get to the question. The question asks, "Which of the following treatments is indicated in this patient at this time?" Option A is low-dose prednisone. Option B is rituximab. Option C is thalidomide. Option D is twice yearly plasmapheresis. Or Option E is no treatment, only yearly serum protein electrophoresis, blood count, creatinine, and calcium.
CATHY: So the answer is E, because there's no treatment that's required for MGUS. Monitoring for progression of the disease is really all that's recommended, and most guidelines will recommend that you repeat labs six months after the initial diagnosis and then repeat the labs again every year. But there's no recommendation to screen for MGUS in the general population though, either.
CHARLIE: What about the other options? Why were they mentioned?
CATHY: The other treatments that are mentioned are therapies that are sometimes used in patients who have a complication like severe neuropathy that's thought to be caused by the monoclonal gammopathy, but that really wouldn't apply in this patient.
CHARLIE: Okay, so the teaching point of this case is the definition of a gamma gap; the definition of an MGUS; and the point that MGUS requires regular follow up but no treatment is indicated in the absence of any symptoms.
CATHY: For more information, you can read about MGUS in Harrison's chapter on Plasma Cell Disorders in Oncology & Hematology. And there's also a good article called, "How I Manage MGUS" in the Blood journal, published in 2018, volume 131, No. 2. ♪ (music) ♪