4.3 TORCH & Congenital Infections

The TORCH Framework

TORCH is a mnemonic for congenital infections that can cross the placenta (or be transmitted perinatally) and cause fetal or neonatal disease: Toxoplasmosis, Other (classically syphilis, but also varicella, parvovirus B19, and others), Rubella, Cytomegalovirus (CMV), and Herpes simplex virus (HSV). Although the individual organisms differ, TORCH infections share overlapping features that make them a natural exam category: intrauterine growth restriction (IUGR), hepatosplenomegaly, jaundice, thrombocytopenia (with petechiae/purpura sometimes described as a 'blueberry muffin' rash -- a sign of dermal extramedullary hematopoiesis seen classically in congenital rubella and CMV, and also in congenital toxoplasmosis and neonatal HSV), microcephaly, and chorioretinitis. The exam skill is recognizing the organism-specific distinguishing feature layered on top of this shared picture, and understanding that timing of maternal infection during pregnancy changes fetal risk.

Comparison Table

Toxoplasmosis

Congenital toxoplasmosis results from maternal infection with Toxoplasma gondii, typically from eating undercooked meat or contact with cat feces containing oocysts. The classic triad -- chorioretinitis, diffuse (not periventricular) intracranial calcifications, and hydrocephalus -- is a frequently tested distractor pair against CMV, which causes periventricular (not diffuse) calcifications. Unlike rubella, transmission risk to the fetus actually increases as pregnancy progresses (higher placental blood flow later in gestation), but the severity of disease is worse with earlier infection, since organogenesis is more vulnerable. Treatment involves pyrimethamine, sulfadiazine, and folinic acid.

'Other': Congenital Syphilis

Congenital syphilis (Treponema pallidum) is the classic member of the 'Other' category and remains clinically important given ongoing global syphilis resurgence. Early congenital syphilis (first 2 years of life) presents with 'snuffles' (a persistent, often blood-tinged nasal discharge), hepatosplenomegaly, lymphadenopathy, and a desquamating maculopapular rash that classically involves the palms and soles. Untreated disease progresses to late congenital syphilis, with stigmata including saber shins (anterior bowing of the tibia), saddle nose deformity, Hutchinson teeth (notched, widely spaced upper central incisors), mulberry molars, and interstitial keratitis. Universal maternal screening (and treatment with penicillin, the only proven effective therapy in pregnancy) is the cornerstone of prevention.

Rubella

Congenital rubella syndrome (CRS) occurs when a non-immune mother is infected with rubella virus, most dangerously in the first trimester, when the risk of major congenital defects can exceed 80-90% with infection before 11 weeks' gestation and falls substantially after 16-20 weeks. The classic triad is sensorineural deafness (the most common single defect), cataracts (sometimes with a 'salt-and-pepper' retinopathy), and cardiac defects, most classically patent ductus arteriosus (PDA) or peripheral pulmonic stenosis. Prevention is via maternal MMR immunity confirmed before pregnancy -- the live MMR vaccine itself is contraindicated during pregnancy.

Cytomegalovirus

CMV is the most common congenital infection worldwide and the leading non-genetic cause of sensorineural hearing loss in children. Most congenitally infected infants (roughly 85-90%) are asymptomatic at birth, but a subset later develop hearing loss, sometimes with delayed onset -- a key reason CMV is tested even in 'asymptomatic' vignettes. Symptomatic infants show periventricular calcifications (versus toxoplasmosis's diffuse calcifications), microcephaly, hepatosplenomegaly, petechiae, chorioretinitis, and sensorineural hearing loss. Unlike the other TORCH organisms, CMV can cause congenital disease after either primary or recurrent/reactivated maternal infection, though primary infection carries substantially higher fetal risk. Diagnosis in the neonate requires viral detection (urine or saliva PCR) within the first 3 weeks of life to distinguish congenital from postnatally acquired infection.

Herpes Simplex Virus

Neonatal HSV differs from the rest of TORCH in that it is usually acquired perinatally, during passage through an infected birth canal, rather than transplacentally in utero (though rare intrauterine transmission occurs). Risk is highest when the mother has a primary (first-episode) genital HSV infection near the time of delivery, because she has not yet developed protective antibody to pass to the fetus; recurrent maternal lesions carry much lower transmission risk. Neonatal HSV presents in three overlapping patterns: skin-eyes-mouth (SEM) disease (localized, best prognosis), central nervous system (CNS) disease (encephalitis, often with seizures), and disseminated disease (multi-organ involvement, highest mortality). Empiric IV acyclovir is started promptly whenever neonatal HSV is a realistic consideration, because delayed treatment significantly worsens outcomes, and cesarean delivery is recommended for mothers with active genital lesions at the time of labor.