Chlamydia trachomatis A-C vs Chlamydia trachomatis D-K and L1-3
How to tell Chlamydia trachomatis A-C and Chlamydia trachomatis D-K and L1-3 apart when a board question makes them look alike.
A-C is eye scarring trachoma; D-K is mucosal urogenital or neonatal infection; L1-3 is invasive lymphogranuloma venereum with painful nodes.
Side by side
Serovars A-C cause trachoma with chronic follicular conjunctivitis, scarring, entropion, trichiasis, corneal opacity, and preventable blindness.
Serovars D-K cause urogenital infection and neonatal conjunctivitis or pneumonia; L1-3 cause lymphogranuloma venereum with transient genital ulcer and painful inguinal nodes.
A-C infect conjunctival epithelium and repeated inflammation scars the eyelid and cornea.
D-K infect mucosal genital and neonatal sites; L1-3 invade lymphatic tissue and produce suppurative lymphadenitis.
Endemic exposure, chronic conjunctivitis, pannus, conjunctival scarring, and trichiasis support trachoma from A-C serovars.
NAAT from genital specimens supports D-K infection; painful buboes after a small ulcer support L1-3 lymphogranuloma venereum.
The trap
All are Chlamydia trachomatis, so the serovar group is inferred from eye scarring, mucosal genital disease, or lymph-node invasion.
The repair move
For Chlamydia trachomatis serovars, locate the disease first: eye, mucosal genital/neonatal, or lymph nodes.
Try a free question
CoreA patient from an endemic region has chronic conjunctivitis, inward-turning eyelashes, corneal scarring, and progressive vision loss. Which serovar group is most likely?
Show answer and explanation
Answer: A. A-C. Chronic scarring conjunctivitis with trichiasis and blindness is trachoma from serovars A-C.
Why the other choices are tempting
- B. D-K causes urogenital infection and neonatal conjunctivitis or pneumonia.
- C. L1-L3 causes lymphogranuloma venereum.
- D. The serovars are clinically distinct by syndrome.
- E. Chlamydia pneumoniae causes respiratory infection, not trachoma.
Flashcards
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Which serovars cause trachoma?
Chlamydia trachomatis serovars A-C cause trachoma.
Which serovars cause common urogenital chlamydial infection?
Serovars D-K cause common urogenital infection and neonatal conjunctivitis or pneumonia.
Quick answers
What is the fastest way to tell Chlamydia trachomatis A-C from Chlamydia trachomatis D-K and L1-3?
A-C is eye scarring trachoma; D-K is mucosal urogenital or neonatal infection; L1-3 is invasive lymphogranuloma venereum with painful nodes.
What is the key clue for Chlamydia trachomatis A-C?
Serovars A-C cause trachoma with chronic follicular conjunctivitis, scarring, entropion, trichiasis, corneal opacity, and preventable blindness.
What is the key clue for Chlamydia trachomatis D-K and L1-3?
Serovars D-K cause urogenital infection and neonatal conjunctivitis or pneumonia; L1-3 cause lymphogranuloma venereum with transient genital ulcer and painful inguinal nodes.
What is the common trap with Chlamydia trachomatis A-C vs Chlamydia trachomatis D-K and L1-3?
All are Chlamydia trachomatis, so the serovar group is inferred from eye scarring, mucosal genital disease, or lymph-node invasion.