Viral exanthems of childhood: Pathology review

A 1 year old boy named Adam is brought to the pediatric clinic by his mother, who is concerned because Adam developed a pink skin rash that began in the trunk and has now spread to the extremities.

On physical examination, the rash appears to be maculopapular. Upon further questioning, she recalls that Adam had a high fever for the past few days, and the rash appeared after the fever went down.

Next you see Rose, a 9 year old girl who came in with her father, due to a very itchy rash all over her body. Her father claims that the rash started 2 days ago after having a mild fever, and that several of Rose’s schoolmates also have the same rash.

Upon physical examination, you notice that the rash involves her face, trunk, and extremities, and presents with different types of lesions, including papules, vesicles, and crusts.

Now, based on the initial presentation, both Adam and Rose seem to have a viral exanthem of childhood, which is a group of eruptive skin rashes caused by viral infection and usually affect children.

Generally, viral exanthems can be macular, papular, maculopapular, or vesicular. A macular rash has macules, which are up to 5 mm in diameter, and completely flat, meaning that you can’t feel them if you run your finger over them.

On the other hand, a papular rash has papules, which are raised bumps that are up to 1 cm in diameter. And a maculopapular has both macules and papules.

Finally, a vesicular rash has vesicles, which are up to 5 mm in diameter, and look like clear blisters filled with fluid. Viral exanthems of childhood include varicella; hand-foot-mouth disease; roseola infantum; measles; rubella; and erythema infectiosum.

Alright, now one of the most common viral exanthems is varicella, more commonly referred to as chickenpox. It is caused by the varicella-zoster virus, or VZV for short, which is a DNA virus, and is also known as human herpesvirus 3 or HHV-3, as it belongs to the Herpesviridae family.

Now, this is a highly contagious airborne virus, meaning it’s transmitted from person to person through respiratory droplets; for example, when an infected person sneezes or coughs.

But the virus can also be transmitted by direct contact with the fluid from vesicular skin lesions of an infected person. Because of that, an important risk factor for varicella involves going to crowded or poorly ventilated public places, such as day-care centers or school, as well as being immunocompromised.