Trachoma (Chlamydia trachomatis A-C)
Overview
Plain-Language Overview
Trachoma is a contagious eye infection caused by the bacterium Chlamydia trachomatis serotypes A-C. It primarily affects the conjunctiva, the thin membrane covering the white part of the eye and the inside of the eyelids. The infection leads to chronic inflammation and scarring, which can cause the eyelids to turn inward, a condition called trichiasis. This inward turning causes the eyelashes to rub against the cornea, leading to corneal damage and potentially permanent blindness if untreated. Trachoma is a major cause of preventable blindness worldwide, especially in areas with poor sanitation and limited access to clean water.
Clinical Definition
Trachoma is a chronic keratoconjunctivitis caused by repeated infection with Chlamydia trachomatis serotypes A-C. The core pathology involves chronic follicular conjunctivitis with progressive conjunctival scarring, leading to entropion and trichiasis. The repeated infections induce an immune-mediated inflammatory response that damages the conjunctival epithelium and underlying tissue. This scarring can cause corneal opacification and vision loss, making trachoma the leading infectious cause of blindness globally. It is transmitted through direct contact with ocular secretions or via fomites and flies. The disease is endemic in resource-poor settings with inadequate hygiene and sanitation.
Inciting Event
Initial infection occurs via ocular contact with infected secretions from an infected person.
Transmission is facilitated by eye-seeking flies (Musca sorbens) that mechanically transfer bacteria.
Poor facial hygiene and close interpersonal contact trigger initial conjunctival infection.
Latency Period
Symptoms typically develop within 5 to 12 days after exposure to infected secretions.
Chronic inflammation and scarring develop over months to years with repeated infections.
Corneal complications and vision loss usually manifest after several years of recurrent disease.
Diagnostic Delay
Early symptoms are often mild and nonspecific, leading to underrecognition.
Limited access to healthcare in endemic areas delays clinical diagnosis and treatment.
Misattribution of conjunctivitis to viral or allergic causes delays appropriate therapy.
Lack of awareness about trachoma as a cause of blindness contributes to delayed diagnosis.
Clinical Presentation
Signs & Symptoms
Chronic conjunctival irritation with redness and discharge
Photophobia and foreign body sensation
Eyelid swelling and tenderness in active infection
Decreased vision in advanced disease due to corneal involvement
Recurrent episodes of conjunctivitis in endemic areas
History of Present Illness
Patients initially report recurrent episodes of red, itchy eyes with discharge.
Progression includes chronic follicular conjunctivitis with conjunctival thickening.
Later stages involve complaints of eye pain, photophobia, and foreign body sensation due to trichiasis.
Visual impairment develops gradually as corneal opacification worsens.
Past Medical History
History of repeated conjunctivitis episodes in childhood or adolescence is common.
Previous treatment with topical antibiotics or traditional remedies may be reported.
Exposure to poor sanitation or endemic environments is often noted.
No specific systemic illnesses are typically associated but immunocompromised states may worsen course.
Family History
No clear heritable genetic predisposition is established for trachoma.
Family members often share environmental risk factors and exposure in endemic areas.
Clusters of cases within families reflect shared living conditions and hygiene practices.
Physical Exam Findings
Follicular conjunctivitis with small, pale follicles on the upper tarsal conjunctiva
Herbert's pits, which are depressions at the limbus caused by resolved follicles
Conjunctival scarring leading to distortion of the eyelid margin
Trichiasis, or inward turning of eyelashes causing corneal irritation
Corneal pannus, a vascularized opacity at the corneal periphery
Diagnostic Workup
Diagnostic Criteria
Diagnosis of trachoma is primarily clinical, based on the presence of follicular conjunctivitis on the upper tarsal conjunctiva, conjunctival scarring, and evidence of trichiasis or entropion. The World Health Organization grading system includes identifying follicles ≥0.5 mm in diameter and conjunctival inflammation. Confirmation can be made by detecting Chlamydia trachomatis using nucleic acid amplification tests (NAATs) from conjunctival swabs. The diagnosis is supported by epidemiological context and characteristic clinical signs.
Pathophysiology
Key Mechanisms
Chronic conjunctival infection with intracellular gram-negative bacterium Chlamydia trachomatis serovars A-C causes persistent inflammation.
Repeated episodes of follicular conjunctivitis lead to conjunctival scarring and distortion of eyelid anatomy.
Inflammation induces fibrosis of the tarsal conjunctiva, resulting in entropion and trichiasis.
Trichiasis causes corneal abrasion and ulceration, leading to progressive corneal opacity and blindness.
Host immune response involves CD4+ T cells and macrophages, contributing to tissue damage and scarring.
| Involvement | Details |
|---|---|
| Organs | Eye is the organ affected by trachoma, with involvement of the conjunctiva and cornea leading to blindness if untreated. |
| Tissues | Conjunctival tissue is the primary site of infection and chronic inflammation causing scarring in trachoma. |
Corneal epithelium is affected secondarily by trichiasis-induced abrasion leading to opacity and vision loss. | |
| Cells | Conjunctival epithelial cells serve as the primary site of Chlamydia trachomatis infection and replication. |
Macrophages mediate chronic inflammation and tissue damage in trachoma. | |
Fibroblasts contribute to conjunctival scarring during the chronic phase of the disease. | |
| Chemical Mediators | Interleukin-1 (IL-1) promotes inflammation and fibrosis in the conjunctiva during trachoma. |
Tumor necrosis factor-alpha (TNF-α) drives chronic inflammatory responses leading to tissue damage. | |
Matrix metalloproteinases (MMPs) degrade extracellular matrix contributing to conjunctival scarring. |
Treatments
Pharmacological Treatments
Azithromycin
- Mechanism:
Inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit of Chlamydia trachomatis.
- Side effects:
Gastrointestinal upset
QT prolongation
Allergic reactions
- Clinical role:
First-line
Tetracycline eye ointment
- Mechanism:
Inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit of Chlamydia trachomatis.
- Side effects:
Local irritation
Photosensitivity
- Clinical role:
Alternative first-line
Non-pharmacological Treatments
Surgical correction of trichiasis to prevent corneal scarring and blindness.
Facial cleanliness and improved hygiene to reduce transmission of Chlamydia trachomatis.
Environmental improvements such as access to clean water to decrease disease prevalence.
Prevention
Pharmacological Prevention
Mass azithromycin administration in endemic communities to reduce transmission
Topical tetracycline ointment for individual prophylaxis in contacts
Non-pharmacological Prevention
Facial cleanliness to reduce ocular secretions and transmission
Improved sanitation and access to clean water to limit spread
Health education programs promoting hygiene and early treatment
Environmental improvements to reduce fly populations that transmit infection
Outcome & Complications
Complications
Corneal ulceration leading to scarring and vision loss
Entropion causing chronic corneal irritation
Blindness from progressive corneal opacification
Secondary bacterial keratitis
| Short-term Sequelae | Long-term Sequelae |
|---|---|
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Differential Diagnoses
Trachoma (Chlamydia trachomatis A-C) versus Bacterial Conjunctivitis (e.g., Staphylococcus aureus)
Trachoma (Chlamydia trachomatis A-C) | Bacterial Conjunctivitis (e.g., Staphylococcus aureus) |
|---|---|
Infection caused by intracellular obligate bacterium Chlamydia trachomatis serovars A-C | Infection caused by extracellular bacteria such as Staphylococcus aureus |
Chronic, recurrent follicular conjunctivitis with gradual progression | Acute onset with purulent discharge and rapid symptom progression |
Positive nucleic acid amplification test (NAAT) for Chlamydia trachomatis | Positive bacterial culture from conjunctival swab |
Trachoma (Chlamydia trachomatis A-C) versus Viral Conjunctivitis (e.g., Adenovirus)
Trachoma (Chlamydia trachomatis A-C) | Viral Conjunctivitis (e.g., Adenovirus) |
|---|---|
Chronic conjunctivitis with repeated episodes and scarring over months to years | Self-limited acute conjunctivitis lasting 1-2 weeks |
Presence of intracytoplasmic inclusion bodies in conjunctival epithelial cells | Presence of lymphocytes and neutrophils in conjunctival smear without intracellular inclusions |
Positive NAAT for Chlamydia trachomatis serovars A-C | Positive viral PCR or antigen test for adenovirus |
Trachoma (Chlamydia trachomatis A-C) versus Trachomatous Keratopathy (Late-stage Trachoma)
Trachoma (Chlamydia trachomatis A-C) | Trachomatous Keratopathy (Late-stage Trachoma) |
|---|---|
Early follicular conjunctivitis without corneal scarring | Advanced scarring with corneal opacification and blindness |
Follicular inflammation with lymphoid follicles and papillae | Dense conjunctival scarring with entropion and trichiasis |
Trachoma (Chlamydia trachomatis A-C) versus Adult Inclusion Conjunctivitis (Chlamydia trachomatis D-K)
Trachoma (Chlamydia trachomatis A-C) | Adult Inclusion Conjunctivitis (Chlamydia trachomatis D-K) |
|---|---|
Infection by Chlamydia trachomatis serovars A-C, transmitted via eye-to-eye contact or fomites | Infection by Chlamydia trachomatis serovars D-K, typically sexually transmitted |
Endemic exposure in children or poor hygiene conditions | History of sexual exposure or genital infection |
Chronic follicular conjunctivitis with conjunctival scarring | Subacute conjunctivitis with mucopurulent discharge |
Trachoma (Chlamydia trachomatis A-C) versus Allergic Conjunctivitis
Trachoma (Chlamydia trachomatis A-C) | Allergic Conjunctivitis |
|---|---|
Chronic inflammation with lymphocytes and follicle formation, no eosinophils | IgE-mediated hypersensitivity with eosinophilic infiltration |
Persistent conjunctivitis with progressive scarring | Intermittent symptoms triggered by allergens, seasonal or perennial |
Requires prolonged antibiotic therapy and hygiene measures | Rapid symptom relief with antihistamines and mast cell stabilizers |