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Congenital cytomegalovirus infection is the infection of a fetus with cytomegalovirus, Or CMV, during intrauterine life. CMV is among the most common infections that cause defects during fetal development. It is often grouped with other bacteria, parasites, and viruses that cause similar illnesses in the newborn, known under the acronym TORCH, which includes Toxoplasma, Other pathogens - usually syphilis; Rubella; Cytomegalovirus, and Herpes simplex virus.

CMV belongs to the herpes viridae family of viruses. Herpes viruses are double-stranded DNA viruses that are surrounded by a lipid envelope. CMV is usually transmitted through contact with blood and other body fluids like breast milk, saliva, genital secretions, and urine of an infected person; or from transplanted organs. Congenital CMV infection occurs when a pregnant woman is infected by CMV for the first time during the pregnancy, or there’s a reactivation of an old infection or reinfection with a new strain of CMV. The virus in the mother travels through the placenta to the growing fetus. The exact mechanism by which CMV causes infection and defects in the developing fetus are still unknown, but it’s thought to be because of two things. First, CMV can be cytopathic, or cell-damaging, as it replicates within the cells. It breaks down the cytoskeletons which maintain the cell structure which results in enlarged cells with intranuclear viral inclusion bodies, giving it the classic “owl's eye” appearance.

It is also possible that CMV slows down the process of mitosis or cell division. Since mitosis helps drive the development of the fetus, tissue with infected cells might not grow properly. Second, CMV invades the endothelium of blood vessels, resulting in vasculitis, or inflammation of blood vessels. Vasculitis can affect placental as well as fetal blood vessels, causing narrowing of the vessel wall. And, as a result, not enough blood flows to developing organs, causing abnormalities. Congenital CMV also increases the risk of intrauterine growth restriction (IUGR), meaning the fetus does not grow well, or oligohydramnios or polyhydramnios, which is increased or decreased amniotic fluid. Most congenital CMV infections are asymptomatic or silent, with only 1 in 10 infected infants showing symptoms at birth.

The most common clinical manifestations include petechiae, which is tiny purple, red, or brown spots on the skin; jaundice, when the skin, whites of the eyes, and mucous membranes turn yellow; hepatosplenomegaly which is enlarged liver and spleen; and microcephaly or an abnormally small head size due to an underdeveloped brain. The hallmark feature of congenital CMV is progressive, permanent sensorineural hearing loss, or deafness, which can present at birth or develop later in life. Congenital CMV is also associated with eye abnormalities such as chorioretinitis, inflammation of the choroid and retina, strabismus, muscle imbalance of the eyes, or cortical vision impairment. CMV also can cause intellectual disability, developmental delays, behavioral disorders, motor disabilities, and seizures.

The diagnosis of congenital CMV infection can be made prenatally, before birth, or postnatally, after birth. Prenatal testing includes ultrasonography of the fetus to detect developmental anomalies, amniocentesis to obtain amniotic fluid for viral culture or CMV PCR, or fetal blood sampling for CMV PCR or cytomegalovirus-specific IgM antibody measurement. After birth, diagnosis is confirmed by PCR or viral isolation from urine or saliva samples in newborns obtained under three weeks of age. A full physical examination of the baby should be done, looking for skin rashes, enlarged liver and spleen, and microcephaly. In addition, babies with congenital CMV should be screened for hearing loss at birth, and periodically during childhood and adolescence. Some hospitals will screen all babies for CMV who fail their newborn hearing screening because CMV can cause congenital hearing loss. Other tests done to assess the extent of the infection may include a liver panel which might show elevated liver transaminases or elevated bilirubin levels, and a full blood count revealing thrombocytopenia or low platelets. Neuroimaging of the brain by ultrasonography, unenhanced CT, or MRI, may be done, which might detect intracranial calcifications, enlarged ventricles, polymicrogyria, lenticulostriate vasculopathy, or white matter disease.

Treatment is usually reserved for symptomatic infants and includes antiviral medications like ganciclovir and valganciclovir, usually given for a total of six months. Antiviral medication has been shown to reduce the risk of hearing loss progressing and improves head size growth and developmental milestones early in life. It does not reverse the damage that’s already occurred. Other supportive measures, such as blood products and platelet transfusions can be given. As the child grows, functional therapies such as physical therapy, occupational therapy, speech/language therapies, and vision therapies also may be needed. Children with hearing loss may be taught sign language, be fitted for hearing aids, or undergo cochlear implant procedures.

Prevention of congenital CMV by the vaccine, like what is routinely done to prevent congenital rubella, is not currently available. Women who wish to reduce their risk of CMV infection during pregnancy should reduce or avoid contact with saliva and urine from toddlers and young children, who often are asymptomatically shedding CMV, and maybe a source of infection.

All right, as a quick recap… Congenital CMV infection occurs when a pregnant woman infected with CMV passes it on to her growing fetus, which results in fetal infection, and May, but not always, result in birth defects. Fetal defects caused by CMV are thought to be caused by a combination of cytopathic effects on fetal cells, and blood vessel injury leading to decreased blood flow to the developing organs. Clinical manifestations include petechiae, jaundice, hepatosplenomegaly, sensorineural hearing loss, eye abnormalities, microcephaly, intellectual disability, developmental delays, behavioral disorders, and motor disabilities such as cerebral palsy, and seizures.

Treatment in the symptomatic newborn and young infant involves antiviral medications like ganciclovir and valganciclovir for a total of six months. Long-term treatment involves therapies to improve milestones, mobility, hearing, speech, and language. A CMV vaccine is not available, but reducing contact with saliva and urine during pregnancy may be helpful to reduce CMV transmission.

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