Question

what is the most common cause of reactive arthritis in a patient with diarrhea and dysuria?

• A. Treponema pallidum
• B. mycoplasma
• C. Salmonella
• D. streptococcus

Hint:

It is always helpful to remember the classic medical mnemonic "Can't see, can't pee, can't climb a tree" to recall the classic triad of reactive arthritis: Uveitis/Conjunctivitis, Urethritis (dysuria), and Arthritis.
These episodes are classically triggered by either GI bugs (such as Salmonella, Shigella, Yersinia) or GU bugs (specifically Chlamydia).

Answer 1

The Correct Option is C

Concept:
A patient presents to the clinic with classic signs of reactive arthritis that explicitly follow a recent history of symptoms suggesting both a gastrointestinal and a genitourinary infection (as indicated by the presence of both diarrhea and dysuria).
The question specifically requires identifying the most common bacterial trigger from the given multiple-choice options that is known to cause this post-infectious, autoimmune-mediated rheumatological syndrome.
Step-by-step Explanation:

• Reactive arthritis (which was formerly and eponymously known as Reiter's syndrome) is a sterile, inflammatory spondyloarthropathy that classically develops several weeks after an initial, often resolved, primary infection located elsewhere in the body.

• It classically and typically presents as an asymmetric oligoarthritis, very frequently involving the large, weight-bearing joints of the lower extremities (like the knees and ankles), and is highly associated with the presence of the HLA-B27 genetic antigen.

• The primary, recognized triggering infections for this syndrome are typically either genitourinary (usually sexually transmitted) or enteric (gastrointestinal) in origin.

• Genitourinary reactive arthritis is by far most commonly triggered by an asymptomatic or symptomatic infection with Chlamydia trachomatis.

• Enteric reactive arthritis is classically triggered by various invasive gastrointestinal pathogens, most notably including Salmonella, Shigella, Yersinia, and Campylobacter species.

• The patient's explicit history of experiencing acute diarrhea strongly points towards an enteric bacterial trigger for their current joint symptoms.

• Among the provided options, Salmonella (Option C) is a highly classic, exceedingly frequent, and well-documented enteric bacterial cause of reactive arthritis.

• Treponema pallidum (Option A) is the spirochete responsible for causing syphilis, which can indeed cause various arthropathies (like Charcot joints in tertiary syphilis), but it is absolutely not a classic trigger for typical reactive arthritis.

• Mycoplasma (Option B) is primarily recognized as a respiratory pathogen causing atypical pneumonia and is an exceedingly rare and unusual cause of reactive joint disease.

• Streptococcus (Option D) is famously known to trigger Rheumatic fever and post-streptococcal reactive arthritis, but this condition nearly universally follows a respiratory pharyngitis, and not a diarrheal illness.
Final Answer:
Given the clear clinical history of preceding diarrhea, Salmonella is the most common enteric pathogen listed among the options that is known to trigger reactive arthritis.