to snoo-finity ... and beyond!
to snoo-finity ... and beyond!
This patient case sounds like he has iron deficiency anemia (anemia, low hematocrit, microcytic) from a GI bleed. To get this question right, you had to remember that the two major inherited GI cancer syndromes are FAP (due to mutation in APC gene, which is a tumor suppressor gene) and Lynch syndrome AKA hereditary non-polyposis colorectal carcinoma (HNPCC), caused by a mutation in a number DNA mismatch repair genes, of with MHS2 is a more common one.
The mechanisms of their carcinoma development are different; in FAP, tumors arise from a normal --> adenoma --> carcinoma sequence while in HNPCC, tumors arise from what's known as a microsatellite instability pathway, leading to spontaneous formation of a carcinoma (not preceded by a benign lesion like an adenoma)... You didn't need to know this to get this question right, but definitely good to know.
I think there's something that hasn't been mentioned and people are over looking:
Patient is presenting with CRC + anemia which most commonly occurs with RIGHT sided cancer. And how does that cancer develop? Micro-satellite instability (vs left sided = obstruction and polyp-adenoma sequence).
Misat instab mostly commonly occurs in HNPCC due to mismatch repair defect.
Thus, even though there's a type in the gene, or even if you don't know the gene, there's enough info to figure out it's HNPCC.
FAP doesn't match the picture, and is a pylop-adenoma sequence cancer. Li-fraumeni is defect in p53 (which is the last stage of pylop-adenoma sequence so I assume it follows that too?).
The constipation is kinda tricky because you'd think obstruction but the big key here is ANEMIA due to CHRONIC BLEEDING.
submitted by charlie(5), 2019-10-06T03:21:02Z
I think there's a typo on that question. MSH2 gene mutation is the culprit for HNPCC. For MHS2 gene, according to what I just searched, causes Malignant Hyperthermia Susceptibility.