BASICS

DESCRIPTION

• Toxoplasmic chorioretinitis is usually a unifocal, full thickness chorioretinal lesion.

• Frequently arises from border of preexisting chorioretinal scar

• Associated with focal vitreous inflammation directly over the lesion

• Anterior segment findings may include mild iritis, large keratic precipitates, raised intraocular pressure.

• Signs and symptoms usually limited to the eye, cerebral form seen in HIV

EPIDEMIOLOGY

Incidence

• Majority of cases assumed to be congenital, although recent publications have challenged this

• There are documented reports of acquired disease in patients with a previously normal fundus and seronegative antibody titers.

Prevalence

• Most common cause of posterior uveitis

• Accounts for 90% of necrotizing retinitis

RISK FACTORS

• Ingestion of raw meat

• Exposure to cats

• HIV

GENERAL PREVENTION

• Avoid modifiable risk factors

• Consider using trimethoprim/sulfamethoxazole in patients with history of toxoplasmosis prior to cataract surgery

ETIOLOGY

• Infestation with an obligate intracellular protozoan, Toxoplasma gondii

• Parasite found in cats. Intermediate hosts include rodents and birds.

• Infestation is usually congenital (transplacental) and occasionally acquired.

• Predilection for the eye and brain.

COMMONLY ASSOCIATED CONDITIONS

• HIV

• Immunocompromised patients and the elderly

DIAGNOSIS

HISTORY

• Young healthy patients with recent onset of blurred vision.

– Photophobia

– Red eye

– Floaters

• Ingestion of raw meat that contains tissue cysts.

• Exposure to cats

• HIV or Immunocompromise

PHYSICAL EXAM

Common ophthalmic features of toxoplasmosis chorioretinitis can include:

• Decreased vision

• Floaters

• Conjunctival erythema

• Moderate to severe vitreous inflammatory reaction

• Focal area of chorioretinal inflammation

• Unilateral pale retinal lesion, with adjacent chorioretinal scar

• Mild anterior uveitis

• Raised intraocular pressure

• Optic disc swelling

Less common ophthalmic features include:

• Pain with severe iridocyclitis

• Large keratic precipitates

• Neuroretinitis with macular star formation

• Retinal artery or vein occlusion

• Cystoid macular edema

• Retinal vasculitis

• Peri-arterial exudation, Kyrieleis arteritis

DIAGNOSTIC TESTS & INTERPRETATION

Lab

Initial lab tests

• Serum IgM and IgG antibodies can be evaluated for presumed acquired infections

• IgM found 2 weeks to 6 months after initial infection

• High percentages of general population are IgG seropositive

• Can compare antibody levels in serum to intraocular fluid (aqueous or vitreous) to confirm intraocular production.

• Polymerase chain reaction (PCR) of the aqueous humor may be useful in atypical cases

• Chest x-ray, luetic screening, Toxocara serology, and TB testing may be helpful when the diagnosis is uncertain.

• HIV testing in atypical cases or patients at risk

DIFFERENTIAL DIAGNOSIS

• Syphilis

• Tuberculosis

• Toxocariasis

• Sarcoidosis

• Acute retinal necrosis (ARN)

• Endophthalmitis

– Endogenous

– Exogenous

TREATMENT

MEDICATION

First Line

Treatment plan based on location and severity

• Small non-sight threatening lesions

– Trimethoprim/sulfamethoxazole

– Second-generation tetracycline

• Sight threatening lesions near disc (2–3 mm) or in macula

– Pyrimethamine, PO 200 mg loading dose, then 25 mg PO daily

– Sulfadiazine 2 g PO loading dose, then 1 g PO q.i.d

– Folinic acid 10 mg PO every second day

Treatment duration is 5–6 weeks

• Steroids

– Low dose (20–60 mg PO daily 2–3 weeks)

– Required to reduce macular or optic nerve inflammation or swelling

– Start minimum of 24 hours after initiation of antibiotics

Discontinue 7–10 days prior to stopping antibiotics

Avoid periocular steroids as they may cause scleritis

• Topical medications: If anterior segment inflammation ± raised IOP

– Steroids, Prednisolone acetate 1% q.i.d

– Cycloplegic agent, Homatropine 2% t.i.d

– Antiglaucoma medications, Timolol maleate 0.5% b.i.d

Second Line

Sulfa allergy: Use Azithromycin, or Atovaquone, or Clindamycin.

ADDITIONAL TREATMENT

Additional Therapies

• Considerations for immunocompromised patients.

– Frequently subclinical inflammation

– May not have preexisting chorioretinal scars

– Multifocal ± bilateral disease can be seen

– Can be relentlessly progressive

– Cerebral form more common, patients require CNS imaging studies

– Delayed treatment can lead to diffuse spreading form mimicking ARN

– Avoid systemic steroid use

– May require long-term maintenance antibiotic therapy

Pregnancy Considerations

• Maternal fetal transmission can cause more severe ocular manifestations.

• Ophthalmic findings in the newborn

– Microphthalmos

– Bilateral macular scars

• CNS findings in the newborn

– Convulsions

– Paralysis

– Hydrocephalus

– Intracranial calcification

– Stillbirth

– Visceral involvement

• Pregnant women seronegative for Toxoplasmosis antibodies should avoid any contact with cats during pregnancy.

• Consult Obstetrician

• Treatment in Pregnancy:

– Clindamycin 300–600 mg PO q.i.d

– Spiramycin 3 g PO in 3–4 doses

– Do not use Pyrimethamine

SURGERY/OTHER PROCEDURES

Vitrectomy may be required for dense vitreitis or other complications such as retinal detachment.

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

• Small non-sight threatening lesions require less stringent follow-up care, but should be assessed 1 week after initiating therapy and then every 2 weeks.

• Sight threatening infections near the optic nerve or macula should be assessed at 3 days and then weekly.

• Usual course of treatment is 6 weeks.

• Avoid delays in treating immunocompromised patients and remember these patients may require long-term antibiotics.

Patient Monitoring

• All patients should have a complete dilated ocular exam on each visit.

• Results of all blood tests and ancillary testing should be attained as soon as possible.

• Patients on Pyrimethamine require weekly CBC testing.

• Fasting blood glucose levels should be determined prior to starting systemic steroid treatment.

DIET

• All patients should be instructed to avoid eating raw or undercooked meat containing Toxoplasma cysts.

• Other dietary risks include raw milk or unfiltered chlorinated surface water.

PATIENT EDUCATION

• All patients should be aware that the major routes of transmission are:

– Ingestion of contaminated foodstuffs; recommend adequate cooking of meat and care handling raw meat

– Contamination of hands from disposing of cat feces or contaminated soil or sand boxes; recommend gloves or hand washing

– Transplacental transmission from infected mother to fetus during gestation; pregnant women should avoid any contact with cats

PROGNOSIS

• 40% of patients may have permanent unilateral visual loss to 20/100 or less

• 90% of patients with macular lesions will experience severe vision loss

• 15% of patients may have mild visual loss (20/40–20/70)

• 5 year recurrence rate is ∼80%

• Vision loss more associated with duration of active episode than number of recurrences

COMPLICATIONS

• Mild to severe vision loss

• Vitreous hemorrhage

• Secondary choroidal neovascularization

• Epiretinal membrane formation

• Chronic and relentless vitreitis

• Retinal tear and detachment

• Cystoid macular edema

• Cataract

CODES

ICD9

• 130.2 Chorioretinitis due to toxoplasmosis

• 130.9 Toxoplasmosis, unspecified

Stay updated, free articles. Join our Telegram channel

Join