Juvenile polyposis syndrome

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Juvenile polyposis syndrome



Juvenile polyposis syndrome


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USMLE® Step 1 questions

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Juvenile polyposis syndrome

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USMLE® Step 1 style questions USMLE

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A 5-year-old boy is brought to the physician by his mother due to excessive fatigue over the past 2 months. The mother has occasionally noticed blood in the toilet bowl after the patient defecates. There is no significant family history of cancers. The patient's temperature is 37.0°C (98.6°F), pulse is 96/min, and blood pressure is 110/70 mmHg. Physical examination shows conjunctival pallor. No abnormal skin pigmentation is noted. Laboratory results are as follows:

 Laboratory Value  Result 
 Hemoglobin  9.7 g/dL 
 Hematocrit  35% 
 Mean corpuscular volume (MCV)  74 μm3 
Colonoscopy is performed and reveals seven polyps throughout the gastrointestinal tract; subsequent biopsy reveals hamartomatous mucosal polyps. Genetic testing is performed and reveals a mutation in the BMPR1A gene. Which of the following is the most likely diagnosis in this patient? 

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In juvenile polyposis syndrome, young children develop multiple polyps throughout the gastrointestinal tract, especially in the large intestine, and unfortunately some of those polyps can develop into colon cancer at some point in their life.

The large intestine is found in the abdominal cavity, which can be thought of as having two spaces - the intraperitoneal space and the retroperitoneal space.

The intraperitoneal space contains the first part of the duodenum, all of the small intestines, the transverse colon, sigmoid colon, and the rectum; the retroperitoneal space contains the distal duodenum, ascending colon, descending colon, and anal canal.

So the large intestines essentially weave back and forth between the intraperitoneal and retroperitoneal spaces.

Now, the walls of the gastrointestinal tract are composed of four layers.

The outermost layer is the serosa for the intraperitoneal parts, and the adventitia for the retroperitoneal parts.

Next is the muscular layer, which contracts to move food through the bowel.

After that is the submucosa, which consists of a dense layer of tissue that contains blood vessels, lymphatics, and nerves.

And finally, there’s the inner lining of the intestine called the mucosa; which surrounds the lumen of the gastrointestinal tract, and comes into direct contact with digested food.


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  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Juvenile polyposis syndrome" World Journal of Gastroenterology (2011)
  6. "Non-Invasive Colorectal Cancer Screening: An Overview" Gastrointestinal Tumors (2020)
  7. "TGFβ signals through a heteromeric protein kinase receptor complex" Cell (1992)

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