Excerpt from Chorioretinitis

Please click here to view the full topic text: Chorioretinitis

Background

Chorioretinitis (CR) is an exudative inflammatory process that involves the retinal vessels and is usually caused by congenital viral, bacterial, or protozoan infections in neonates. Congenital toxoplasmosis (CTP) is the most common cause of infectious chorioretinitis in immunocompetent children. Congenital cytomegalovirus (CMV) infection is the second most common etiology. Fungal infections are more frequently identified, and emergent pathogens, including West Nile virus and lymphocytic choriomeningitis virus, have been described. In rare instances, chorioretinitis is part of a systemic noninfectious process.

In the older pediatric age group, chorioretinitis is diagnosed in diverse clinical conditions and can reflect newly acquired diseases or reactivation. Chorioretinitis can result from a dissemination of Toxocara or Baylisascaris in immunocompetent patients. In severely immunodeficient patients, including those with acquired immunodeficiency syndrome (AIDS), chorioretinitis may be associated with Epstein-Barr virus (EBV), CMV, varicella-zoster virus, various fungi (eg, Candida, Aspergillus, Fusarium, dimorphic fungi), and Toxoplasma.

Pathophysiology

Chorioretinitis causes an inflammation of the retinal vessels in reaction to a generalized infection that involves multiple organ systems. Congenital disseminated infections also manifest as intrauterine growth retardation, microcephaly, microphthalmia, cataract, uveitis, hearing defect, osteomyelitis, enlarged liver and spleen, lymphadenopathy, dermal erythropoiesis, carditis, and congenital heart disease. Vessel trauma caused by lodging Toxocara or Baylisascaris larvae may be associated with severe inflammatory responses.

Although chorioretinitis that is associated with congenital viral infections tends to be stable or improves in infancy, chorioretinitis associated with asymptomatic CTP progresses for years after birth and is more likely to be clinically significant at an older age.

Frequency

United States

CTP occurs much less frequently in the United States than in several European countries. Chorioretinitis is extremely rare in children, regardless of immunologic status.

Worldwide, chorioretinitis due to CTP is more common than chorioretinitis due to symptomatic congenital CMV. The seroprevalence rate in childbearing women is estimated at 14-30%, and the estimated incidence rate of CTP is 0.1 per 1000 births.

Statistically, chorioretinitis due to CMV is more common than chorioretinitis due to CTP in the United States. Chorioretinitis occurs in approximately 14% of infants born with symptomatic congenital CMV infection. However, severely affected infants represent fewer than 10% of those with congenital infections due to maternal primoinfection with viremia during the first half of pregnancy. Chorioretinitis affects only 2% of asymptomatic infants with congenital infection.
 
Toxocara canis–associated ocular larva migrans occurs in more than 60% of symptomatic seropositive children. This zoonosis is probably one of most commonly acquired childhood eyesight impairments because of the high prevalence of young pet dogs in the United States.

International

Seroprevalence rates for CTP in childbearing women are 50-80% in European countries, and the estimated incidence rate of CTP is 1-4 cases per 1000 births. However, acquired toxoplasmosis accounts for a much higher rate of ocular infections in late childhood worldwide. The prevalence of CMV seroconversion in many parts of the world reaches almost 100% in young adults. The incidence of CMV congenital infection is not well documented.

Mortality/Morbidity

• If left untreated or if the condition does not respond to treatment, severe chorioretinitis can result in partial or total loss of vision in the affected eye.
• Morbidity is due to concurrent damage to major organ systems, especially damage to the brain (eg, developmental delays, seizures). 
• Mortality due to chorioretinitis depends on the nature and progression of the basic illness.

Age

• Congenital chorioretinitis is usually evident at birth.
• Congenital chorioretinitis associated with CTP actively progresses after birth and manifests when the individual is aged 5 years.
• Acquired chorioretinitis occurs at any age, depending on the disseminated illness.

Please click here to view the full topic text: Chorioretinitis