TORCH & Congenital Infections
The perinatal infections that scar the fetus, and how to tell them apart
TORCH overview
The pathogens. TORCH stands for Toxoplasma, Other (syphilis, Listeria, parvovirus B19, VZV, Zika, HIV), Rubella, CMV and HSV. Most cross the placenta; HSV-2 is the exception, acquired peripartum in the birth canal. Maternal infection is often mild or silent, so the diagnosis is usually made in the infant.
Shared findings. Many of these infections produce the same nonspecific picture: IUGR, hepatosplenomegaly, jaundice, thrombocytopenia and rash. That overlap is the rule. The specific triads and the pattern of intracranial calcification make the diagnosis.
The classic triads: toxoplasmosis, CMV and rubella
Toxoplasmosis. Toxoplasma gondii is acquired from cat feces or undercooked meat. The classic triad is hydrocephalus, diffuse intracranial calcifications and chorioretinitis. Pregnant women should avoid cat litter and raw or undercooked meat.
Cytomegalovirus. CMV is the most common congenital infection and the leading nonhereditary cause of sensorineural hearing loss. Symptomatic infants have periventricular calcifications, microcephaly, seizures and a petechial blueberry muffin rash, and chorioretinitis can also occur. Most infected newborns look normal at birth, and hearing loss may appear only later. Valganciclovir reduces hearing loss.
Location separates the two calcifiers: CMV calcifications hug the ventricles (periventricular), while toxoplasmosis scatters them diffusely through the brain parenchyma.
Rubella. The congenital rubella triad is patent ductus arteriosus (with or without pulmonary artery stenosis), cataracts and sensorineural deafness, plus a blueberry muffin rash. Damage is worst after first-trimester infection. Pre-pregnancy MMR prevents it; because MMR is a live vaccine, it is given before pregnancy, never during.
| Feature | Toxoplasmosis | CMV | Rubella |
|---|---|---|---|
| Triad | Hydrocephalus, calcifications, chorioretinitis | Hearing loss, periventricular calcifications, microcephaly | PDA, cataracts, deafness |
| Calcifications | Diffuse, scattered | Periventricular | Not a defining feature |
| Blueberry muffin rash | Not classic | Yes | Yes |
| Prevention | Avoid cat litter and undercooked meat | No vaccine | MMR before pregnancy |
Syphilis and HSV
Congenital syphilis. Treponema pallidum crosses the placenta. Early disease brings snuffles (rhinitis), a maculopapular rash on the palms and soles and hepatosplenomegaly, and the rhinitis can destroy nasal cartilage to produce a saddle nose. Late disease leaves Hutchinson (notched) teeth, mulberry molars, saber shins and CN VIII deafness. Treating the mother with penicillin prevents it, which is why every pregnancy is screened.
| Feature | Early (under 2 yr) | Late (over 2 yr) |
|---|---|---|
| Nose | Snuffles (rhinitis) | Saddle nose |
| Skin and viscera | Palm and sole rash; hepatosplenomegaly | Rhagades (scars at the corners of the mouth) |
| Teeth, bones, senses | Osteochondritis | Hutchinson teeth, mulberry molars, saber shins, interstitial keratitis, CN VIII deafness |
Hutchinson triad: Hutchinson teeth, interstitial keratitis and CN VIII deafness.
Neonatal HSV. HSV-2 is acquired peripartum from active genital lesions, not transplacentally. It presents as skin, eye and mouth (SEM) disease, CNS encephalitis or disseminated disease. Deliver by cesarean if active lesions are present, and treat the neonate with IV acyclovir.
Other congenital infections
Parvovirus B19. The virus infects erythroid precursors, causing fetal anemia, high-output heart failure and hydrops fetalis, and it can cause miscarriage. In children it causes slapped-cheek fifth disease.
Varicella. Maternal VZV in early pregnancy can cause congenital varicella syndrome: limb hypoplasia, cicatricial (dermatomal) skin scarring, chorioretinitis and cataracts. Risk is highest in weeks 8 to 20. Maternal chickenpox just before delivery is a different danger: the newborn is infected before protective maternal IgG has crossed, so it receives varicella immune globulin.
Listeria monocytogenes. Acquired from unpasteurized dairy and deli meats, it crosses the placenta and causes granulomatosis infantiseptica (disseminated granulomas), amnionitis, preterm birth, and neonatal sepsis or meningitis. Ampicillin is the treatment. Pregnant women should avoid soft cheeses and cold cuts.
Zika virus. This flavivirus is spread by Aedes mosquitoes and sexually. It causes severe microcephaly, intracranial calcifications (typically subcortical) and ocular defects. Pregnant women are advised against travel to endemic areas.
HIV. Transmission can occur in utero, during delivery or through breastfeeding. Maternal antiretroviral therapy that suppresses the viral load, plus infant prophylaxis, makes transmission rare.
Blueberry muffin rash and prevention
Blueberry muffin rash. These blue-purple skin lesions are dermal extramedullary hematopoiesis, classically seen in congenital rubella and CMV, usually alongside hepatosplenomegaly, jaundice and thrombocytopenia.
Screen the rest. Routine prenatal screening covers syphilis (RPR/VDRL), rubella immunity, HIV and hepatitis B. What cannot be screened away can often be prevented:
- Behavior: avoid cat litter and raw meat (Toxoplasma), unpasteurized foods (Listeria) and travel to Zika-endemic areas.
- Vaccines: give MMR and varicella before pregnancy; live vaccines are contraindicated during pregnancy.
- Treatment in pregnancy: penicillin for maternal syphilis; antiretroviral therapy for HIV.
- Delivery: cesarean section for active genital HSV lesions.