Posterior Uveitis Due to Toxoplasmosis Definition

Focal chorioretinal inflammation caused by infection.

Epidemiology: This clinical syndrome is encountered frequently.

Pathogenesis: The pathogen, Toxoplasma gondii, is transmitted by ingestion of tissue cysts in raw or undercooked meat or by oocysts from cat feces. In congenital toxoplasmosis, the child acquires the pathogen through transplacen-tal transmission.

Symptoms and diagnostic considerations: As a general rule, a negative complement-fixation test does not exclude Toxoplasma infection where classic clinical symptoms are present. Both forms of the disorder present with characteristic grayish white chorioretinal focal lesions surrounded by vitreous infiltration and associated vasculitis (Fig. 12.34). In congenital toxoplasmosis, the affected children have a macular scar that significantly impairs visual acuity. This often leads to secondary strabismus. Intracerebral involvement can also result in hydrocephalus and intracranial calcifications. In the acquired form, visual acuity is impaired only where the macula is involved. This is rarely the case.

H Congenital toxoplasmosis results in a macular scar that significantly impairs visual acuity.

Differential diagnosis: Chorioretinitis with tuberculosis, sarcoidosis, bor-reliosis (Lyme disease), or syphilis should be excluded by serologic studies.

Treatment: The treatment of choice consists of a combination of pyrimethamine, sulfonamide, folinic acid, and steroids in their respective standard doses.

Prophylaxis: Avoid raw meat and cat feces.

Recurrent toxoplasmosis.

Recurrent toxoplasmosis.

Macular Scar Differential
Fig. 12.34 Acute grayish white chorioretinal focal lesion (arrow) and brownish white chorioretinal scars (arrowhead). Lesions usually recur at the margin of the original scar, the "mother spot".

Clinical course and prognosis: Posterior uveitis due to toxoplasmosis usually heals without severe loss of visual acuity where the macula is not involved. However, it can recur at any time. There is no cure for the congenital form.

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