USMLE® Step 1 style questions USMLE
A 32-year-old man comes to the office with complaints of pain in the hip joint and stiffness in the lower back for the past month. The symptoms are worse in the morning and improve with activity and exercise. Review of systems reveals intermittent abdominal pain and frequent episodes of small-volume bloody diarrhea for the last 3 months. He tried over-the-counter analgesics, which helped the joint pain but made the diarrhea worse. He does not have any pain with urination and has not traveled recently. The remainder of his history is noncontributory. Vitals are within normal limits. BMI is 22 kg/m2. Physical examination shows mild tenderness in the hip joints and limited spinal flexion. Laboratory analysis is shown below:
|Complete blood count|
Plain radiographs show signs of sacroiliac joint inflammation. Which of the following is the most likely cause of this patient’s joint pain?
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Tanner Marshall, MS, Vincent Waldman, PhD, Jahnavi Narayanan, MBBS
Inflammatory bowel disease can cause inflammation in the small and large intestine, in other words...inflammation of the bowel.
Colitis refers specifically to inflammation in the colon, or the large intestine. Ulcerative colitis is a type of inflammatory bowel disease that tends to form ulcers along the inner-surface or lumen of the large intestine, including both the colon and the rectum.
These ulcers are spots in the mucosa where the tissue has eroded away and left behind open sores or breaks in the membrane.
Sometimes there is a flare which means that new damage has occurred, and then there are periods of remission when the tissue starts to heal up.
Ulcerative colitis is actually the most common type of inflammatory bowel disease, not that there are that many, but this one causes inflammation and ulcers in the mucosa and submucosa of the large intestine only, which is an important point that sets it apart from Crohn disease, another inflammatory bowel disease.
Now although certain environmental factors like diet and stress were once thought to be the culprit behind these ulcers forming in the gut, now it’s thought that these are more secondary, meaning they seem to make symptoms worse, but ulcerative colitis is now ultimately thought to be autoimmune in origin.
In fact, cytotoxic T cells from the immune system are often found in the epithelium lining the colon, so the thought is that inflammation and ulceration in the large intestine is caused by T cells destroying the cells lining the walls of the large intestine, leaving behind these eroded areas or ulcers.
It’s unclear what exactly these T cells are meant to be targeting though.
Some patients have p-ANCAs in their blood, or perinuclear antineutrophilic cytoplasmic antibodies, which are a kind of antibodies that target antigens in the body’s own neutrophils.
Although not completely understood, some theories suggest this may be partly due to an immune reaction to gut bacteria that have some structural similarity to our own cells, allowing antibodies to those gut bacteria, or p-ANCAs, to “cross-react” with neutrophils.
Patients also seem to have a higher proportion of gut bacteria that produce sulfides, and often high sulfide production is correlated with periods of active inflammation as opposed to remission.
Ultimately, though, these are mostly correlations and theories, and we’ve yet to nail down the precise mechanism behind mucosal destruction; the cause is ultimately some combination of environmental stimuli, perhaps the sulfide-producing bacteria, mixed with a genetic predisposition, because patients with a family history of ulcerative colitis are more likely to develop the disease themselves.
It also seems to be more common in young women from the teens to 30s, with more prevalence among caucasians and eastern european jews.
Ulcerative colitis is a type of inflammatory bowel disease that causes inflammation and ulcers in the mucosa and submucosa of the large intestine, specifically in the colon and rectum. The cause of the disease is believed to be autoimmune in origin, with cytotoxic T cells destroying the cells lining the walls of the large intestine, leaving behind eroded areas or ulcers. Environmental stimuli and genetic predisposition also play a role. Diagnosis typically requires colonoscopy and radiological imaging. Treatment includes anti-inflammatory medications, drugs that suppress the immune system, and biologic treatments. In severe cases, colectomy may be necessary.