WBR0638

Author	[[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biochemistry, MainCategory::Pathology
Sub Category	SubCategory::Dermatology, SubCategory::General Principles
Prompt	[[Prompt::A 48-year-old diabetic patient presents to the wound care clinic for a new 4 cm right foot ulcer he recently discovered while showering. The patient has a history of poorly controlled diabetes and 2 previous ulcers on his left foot one of which led to a toe amputation. While examining the patient, you note a large ulcer, approximately 1 cm deep, with a bright red base and a clean border. You also notice a smaller 2 cm ulcer that is almost completely healed. Compared to the larger ulcer which of the following is more abundant in the smaller ulcer?]]
Answer A	AnswerA::Collagen type 1
Answer A Explanation	AnswerAExp::Collagen type 1 is the most important component of a healed scarred wound. It is formed in the remodeling phase of wound healing and it replaces collagen type 3 to give the scar better strength.
Answer B	AnswerB::Collagen type 2
Answer B Explanation	AnswerBExp::Collagen type 2 is seen in cartilagenous structures like the distal ends of long bones, the vitreous body, and the nucleus pulposus but not in healing wounds.
Answer C	AnswerC::Collagen type 3
Answer C Explanation	AnswerCExp::Collagen type 3 is important in granulation tissue during wound healing. It is replaced by collagen type 1 seen in healed scars. Collagen type 3 would be more abundant in the larger unhealed ulcer in our patient.
Answer D	AnswerD::Collagen type 4
Answer D Explanation	AnswerDExp::Collagen type 4 is also known as basal membrane or basal lamina. It is needed for tissue integrity and cellular attachments. It is not more abundant in healed wounds.
Answer E	AnswerE::Elastin
Answer E Explanation	AnswerEExp::Elastin content is a property of tissue type and is not usually increased in scar tissue.
Right Answer	RightAnswer::A
Explanation	[[Explanation::Wound healing involves 2 major processes. After the initial inflammatory reaction subsides, the first phase known as the proliferative phase begins. It usually occurs 2-4 days after the initial wound and involves deposition of highly vascularized granulation tissue and wound contraction. Granulation tissue is typically high in reticulin (collagen type 3) content. Approximately 1 week after the initial wound, the second phase of wound healing begins known as the remodeling phase. It can last up to several months depending on the wound size. During this phase, collagen type 3 is replaced by collagen type 1 which gives the healed wound better strength. After this phase a healed scar replaces the wound site with tensile strength usually greater than the original unscarred skin due to its fibrotic nature high in collagen type 1 content. In this patient, the small healed healed ulcer would be high in collagen type 1 compared to the larger active ulcer which would be high in reticulin content. Educational Objective: Healed scar tissue is usually high in collagen type 1 content, compared to an actively healing wound with granulation tissue that would be composed mostly of collagen type 3. References: Kirsner RS, Eaglstein WH. The wound healing process. Dermatol Clin. 1993;11(4):629-40.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Collagen, WBRKeyword::Scars, WBRKeyword::Granulation tissue, WBRKeyword::Reticulin, WBRKeyword::Collagen type 1
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