Dermatology MCQ - Viral Infections - TORCH syndrome

A newborn is noted to have microcephaly, intracranial calcifications, and a purpuric rash described as "blueberry muffin" lesions. The mother reports a mild flu-like illness with a rash during the first trimester of pregnancy. Which of the following is the most likely causative agent and the primary mode of transmission to the fetus?

A) Toxoplasma gondii; transplacental transmission
B) Rubella virus; transplacental transmission
C) Cytomegalovirus; transplacental transmission
D) Treponema pallidum; transplacental transmission
E) Parvovirus B19; transplacental transmission

Correct Answer: B) Rubella virus; transplacental transmission

Explanation

This presentation is classic for congenital rubella syndrome, a component of the TORCH infections (Toxoplasmosis, Other [syphilis, varicella-zoster, parvovirus B19], Rubella, Cytomegalovirus, Herpes simplex).

Key Clinical Features of Congenital Rubella Syndrome:

• Classic Triad:

  1. Sensorineural deafness (most common)

  2. Congenital heart disease (e.g., patent ductus arteriosus, pulmonary stenosis)

  3. Cataracts

• Other Features:

  • Microcephaly and intracranial calcifications

  • "Blueberry muffin" rash: Dermal erythropoiesis presenting as purpuric macules and papules.

  • Hepatosplenomegaly, thrombocytopenia, and intellectual disability.

• Maternal History: Often a history of a mild febrile illness with a rash (maternal rubella) during the first trimester.

Virologic Features and Transmission:

• Causative Agent: Rubella virus (a togavirus).

• Transmission: Transplacental transmission from an infected mother to the fetus, especially during the first trimester when the risk of congenital anomalies is highest (~85%).

• Pathogenesis: The virus causes necrotizing vasculitis and endothelial damage in fetal tissues, leading to ischemia and malformations.

Why Not the Other Options?

• (A) Toxoplasma gondii: Causes intracranial calcifications and chorioretinitis, but the classic rash is not "blueberry muffin" (more associated with rubella or parvovirus B19). Transmission is transplacental or via ingestion of undercooked meat.

• (C) Cytomegalovirus (CMV): The most common congenital infection. Causes microcephaly, intracranial calcifications, and petechiae, but sensorineural hearing loss and chorioretinitis are more typical than the classic triad of rubella. "Blueberry muffin" rash is less common.

• (D) Treponema pallidum: Causes congenital syphilis with rhagades, snuffles, saber shins, and a maculopapular rash, but not typically "blueberry muffin" lesions or cataracts. Transmission is transplacental.

• (E) Parvovirus B19: Can cause hydrops fetalis and anemia with dermal erythropoiesis ("blueberry muffin" rash), but not microcephaly, cataracts, or heart defects characteristic of rubella. Transmission is transplacental.

Management:

• Prevention: MMR vaccination of seronegative women before pregnancy is crucial.

• Prenatal diagnosis: Serologic testing and PCR of amniotic fluid if maternal infection is suspected.

• Supportive care: For affected infants (e.g., cardiac surgery, hearing aids).

Prognosis:
Poor; congenital rubella syndrome leads to lifelong disabilities. highlights the importance of vaccination.

Note: The "blueberry muffin" rash results from extramedullary hematopoiesis due to viral suppression of fetal bone marrow. While classically associated with rubella, it can also be seen in congenital CMV and parvovirus B19 infections. However, the full triad of findings (eye, heart, ear) is most specific for rubella.