Cytomegalovirus CMV

Question 1

Define

Answer 1

DNA virus from the Herpes family

Types of HHV: Sites of latent infection:

HHV-1, HHV-2 (HSV 1 and 2)

HHV-3 (VZV) Dorsal root ganglia

HHV-4 (EBV) B cells

HHV-5 (CMV) Monocytes

HHV-6 (Roseolovirus)

HHV-7 (Roseolovirus)

HHV-8 (Kaposi’s sarcoma-associated HV)

 

Most common congenital infection (0.5-1 in 1,000)

10% complications before birth

10% complications after birth

80% no complications

Question 2

Aetiology

Answer 2

Aetiology – sexual contact, blood-borne, bodily fluids (saliva, urine), vertical

Risk factors – higher socioeconomic class (no childhood immunity), immunosuppression

Epidemiology – 50% immunity in pregnant women, 1% seronegative will contract CMV antenatally, most common congenital viral infection and most common cause of congenital deafness in the UK

Question 3

Signs and Symptoms

Answer 3

(Chorioretinitis is more common in congenital toxoplasmosis)

Mother:

Often asymptomatic (or non-specific: fever, malaise, fatigue)

May have lymphadenopathy

• 30-40% vertical transmission (any stage of pregnancy) SNHL = Sensorineural Hearing Loss

Child

Child (throughout life):

 

90% (birth) -> asymptomatic

10% develop SNHL

 

10% (birth)  Congenital CMV

• 65% have SNHL
• Peri-ventricular calcification
• Chorioretinitis  cataracts
• Jaundice ± ‘blueberry muffin’ rash
• IUGR
• Microcephaly
• Hepatosplenomegaly

Question 4

Investigations

Answer 4

Prenatal diagnosis -> PCR of virus (>21w GA)

Postnatal diagnosis -> PCR of virus (<21d neonate; +ve result beyond this will not confirm congenital CMV)

Urine, salivary swab, blood

Serology (CMV IgM)

 

Maternal serology – seroconversion (2 samples: IgM -ve to IgM +ve) or low-avidity IgG

IgM can persist for months, so a single IgM value alone is insufficient to diagnose CMV primary infection and the raised IgM has to be new finding in previous IgM -ve at booking (i.e. seroconversion)

 

USS of foetus

Amniocentesis PCR – 6-9 weeks after primary infection

Question 5

Complications

Answer 5

Increased risk of miscarriage and stillbirth

• Congenital CMV IUGR, microcephaly, periventricular calcifications, blindness, sensorineural deafness, hepatosplenomegaly, skin rash, pneumonitis, mental retardation

 

Prognosis -> rate of transmission to foetus is 40%, 10% of these develop congenital syndrome

• 90% babies symptomatic at birth will later have neurodevelopmental problems