UWorld Step 1 Qbank: Your world of learning. Subscribe now.

NBME 20 Answers

nbme20/Block 4/Question#3
A 23-year-old woman comes to the physician ...
Collagen synthesis🔍

Login to comment/vote.

This is a keloid. In normal wound healing type 3 collagen is first synthesized and then degraded by Matrix metalloproteinase (a collagenase which uses Zinc as a cofactor) and replaced by Type 1. In a Keloid an excessive amount of disorganized Type 3 collagen persists. Therefore the defect is in Collagen synthesis (Type 1 synthesis)

dulxy071  Wouldn't Granulation tissue be the (more correct) answer since the initial collagen laid down for wound healing is Type III collagen which is consistent of granulation tissue? Collagen is a vast for so many types of itself as we know +2  
kpjk  @dulxy071 she had a surgery 3 months ago healing was fine even uptill 6 weeks ago so the abnormality occurred during remodeling- when type 3 is replaced by type 1 collagen, so the answer wouldnt be granulation tissue +3  

 +3  upvote downvote
submitted by dbg(90),

Imo, this answer choice is wrong, there is no problem in the process of collagen "synthesis" per se. The issue is with excessive synthesis and disorganized deposition. Not an 'abnormal synthetic process' - as would be in EDS, MF, Menkes, etc.

whoissaad  Exactly my reasoning for not choosing collagen "synthesis" +1  

 -3  upvote downvote
submitted by celeste(62),

Sounds like a hypertrophic scar. "Hypertrophic scars contain primarily type III collagen oriented parallel to the epidermal surface with abundant nodules containing myofibroblasts, large extracellular collagen filaments and plentiful acidic mucopolysaccharides." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3022978/

johnthurtjr  I think it may actually be a keloid, not a hypertrophic scar, as it expands beyond the borders of the original incision. +2  
thepacksurvives  I believe this is a keloid; a hypertrophic scar does not extend past the borders of it's original incision, while a keloid does. regardless, the answer to this question is the same :) +  
breis  First AID pg 219 Scar formation: Hypertrophic vs. Keloid +  
charcot_bouchard  They give granulation tissue is a option which is type 3 collagen. so if it was hypertrophic scar it would be ap problem since its only excessive growth of Type 3. while keloid is excessive growth of both 1 and 3 +3  
bharatpillai  I literally ruled put collagen synthesis defect since this is not a collagen synthesis defect at all ( EDS, Scurvy) :/ hate these kind of questions +  

UWorld Step 1 Qbank: Your world of learning. Subscribe now.