Congenital Toxoplasmosis And Clinical Disease

Although there are certain clinical signs that may be present in the infant with symptomatic congenital toxoplasmosis, the ability to diagnose this condition on clinical grounds is often problematic. The spectrum of disease manifestations may vary widely and mimic other transplacentally or perinatally acquired infections. Also, the majority of congenitally infected infants (approx 70-90%) are asymptomatic at birth (1,3,4,24-27). Many of these infants will not have any signs or symptoms until months to years later, when they present with significant clinical sequelae, most frequently affecting the eye or the brain (27-32). In many cases, this may not be caused as much by delayed onset of disease as late recognition of the condition (1).

Some 20% of asymptomatic neonates have been noted previously to have clinically silent ocular or neurological disease (1,31). Disease with delayed onset occurs most often among premature infants, usually during the first 3 months of life. Ocular disease can reactivate months or even years later among immunocompetent as well as immunocompromised patients. There is, however, as yet no reliable method of predicting which infants will develop subsequent complications (27). Thus, it is important to diagnose congenital toxoplasmosis early and start specific therapy to lessen the possi bility of such complications. Unless the primary care provider has a high index of suspicion for congenital toxoplasmosis, the diagnosis may be missed and the infant not treated appropriately until after blindness, mental retardation, or even death has occurred. A small percentage of congenitally infected infants may continue to have sub-clinical infection that may not be detected unless the condition is suspected.

A neonate presenting with overt symptomatic disease may have the classic triad of hydrocephalus (secondary to periaqueductal stenosis), intracranial calcifications, and chorioretinitis (typically bilateral, focal, necrotizing retinitis). This triad, however, occurs in only a minority of symptomatic patients (27,33). The clinical manifestations are usually protean and include one or more of the following manifestations, which occur in more than 50% of affected infants: diffuse maculopapular rash, generalized lym-phadenopathy, hepatosplenomegaly, jaundice, ocular disease (cataracts, microphthalmia, optic atrophy, and chorioretinitis), abnormal spinal fluid, convulsions, fever, and anemia (1,27,34).

Congenitally infected infants born to mothers dually infected with both Toxoplasma and HIV-1 are also at high risk for having HIV-1 infection (35-38). Although these infants may be asymptomatic during the neonatal period, they may subsequently develop rapidly progressive HIV-1 disease complicated by clinically apparent congenital toxoplasmosis.

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