pediatric housecalls Robert R. Jarrett M.D. M.B.A. FAAP

Numbered Diseases of Childhood: FIFTH Disease – Erythema Infectiosum

April 15, 2014

Remember a couple-three weeks ago, when we started this little vintage trek through “the Numbered Diseases of childhood”, I sort of poked fun at the new-fangled-kid doc who sat in the back row and thought that a “pox” was a “rash”?

The “slapped cheek” appearance of FIFTH disease.Well, this is his favorite disease. We are now on part six of The Numbered Rashes series and Erythema Infectiosum – or as the kid doc calls it: “fifth‘s Disease.”

Back in 1905 when they tried the experiment of numbering all the then-known rash diseases – this one fell at number five, FIFTH Disease. So no, even though the spikey-haired fella’ without a tie who calls patients by their first names calls this “fifth‘s disease” – there was no Dr. Fifth.

Of course, as we have seen, the numbering system for rash diseases went away almost before it got started and the other diseases now go by their longer names. All, that is, except this one. Erythema Infectiosum (EI) is just too hard on the tongue so “FIFTH disease” just stuck.

FIFTH Disease – Erythema Infectiosum

Unlike FOURTH disease whose presentation was too difficult to notice easily, FIFTH disease usually gives no problem in its diagnoses – that is IF the person actually develops the rash. Some of them don’t and there-in lies the rub.

Like we said, the presentation of this disease is quite a bit distinct from the whole lump of measles rashes early doctors were trying to get control over. At the turn of the century (1800) this was already being noticed to be “different” or a “variant” of the rash diseases. In 1896 it was accepted as its own disease. In 1899 it got its own name – Erythema Infectiosum and then FIFTH disease in 1905.

Not until 1975 was it know that the disease was caused by a virus, when Australian virologist Yvonne Cossart serendipitously found the thing growing in her lab sample number B-19 while looking for something else; and the rest, as they say, is history: Erythrovirus (or Parvovirus) “B19”.

Incubation – Prodrome

Not the same Parvovirus as found in dogs, Parvovirus B19 infects humans only, through contaminated respiratory “droplets,” but it does have a blood phase so can be transmitted through blood products as well.

Teenage boy with classic, lacy body rash of FIFTH disease.The virus has no fatty coat like most DNA viruses which makes it very resistant to usual “killing” methods like disinfectants and freezing and FIFTH disease is but one of several expressions of this virus (see below).

It is considered fairly contagious with about a 50% chance other non-immune household contacts will be secondarily infected and 25% of the child’s classroom contacts; but, most of that spreading goes on before the child even feels that they are sick.

After exposure and infection, the virus will replicate in the mucous tissues and blood stream for between 4 days and two weeks before producing any symptoms… if it’s going to. Studies show that although 40% to 60% of adults worldwide have laboratory evidence of a past parvovirus B19 infection, most can’t remember having had symptoms of fifth disease.

Disease Course

Then only about 10-20% of patients might experience a bit of a low-grade fever, tiredness, feeling “yukky,” itching or sore throat. There is no lymphadenopathy (swollen glands) and older individuals might experience some joint pain. These symptoms usually subside within two or three days and the patient then feels well for sometimes up to 10 days before the rash develops… maybe.

Only about 75% of children (50% of adults) who are infected then go on to: The Rash – one of the most characteristic rashes in all of childhood exanthems. Once the rash develops they probably aren’t contagious any more, unless they are already immune compromised or are destined to be one of the “recurrent” infections (see below).

There are usually three stages of the rash which may overlap each other, all easily defined:

Rash of FIFTH disease on back of child.Facial erythema, commonly known as the “slapped cheek” phase, consists of red papules on the cheeks which coalesce within hours to form a red, slightly edematous, warm area, symmetric on both cheeks but sparing the bridge of the nose and the region around the mouth. This rash fades in about 4 days.

The body rash begins next with a pattern which resembles a “net” or “lace.” This pattern is so unique that it is evidence of a Parvovirus B19 infection and begins first on the arms and legs about 2 days after the facial rash. It then extends to the trunk and buttocks and fades in 6 to 14 days. (Less commonly the body rash begins with uniform redness and does not become characteristic lace until irregular clearing takes place.)

Recurrences (the third phase) can come and go over the next 2 to 3 weeks, or several months, and seem “triggered” by temperature changes, emotional upsets or sunlight.

Eventually the rash fades without scaling or pigmentation. Treatment – well, being a virus there is none. The only thing we can do is treat the symptoms, if any, and any complications that might develop (see below).

The Rest Of The Story

Unfortunately, we haven’t yet talked about another of FIFTH disease’s unique traits – it shuts off the body’s blood production and crosses the placenta! Red blood cells to be exact and causes danger to a developing baby to be precise.

Chronic Blood Dyscrasias

This little Parvovirus beast crosses into the blood and shuts off red blood cell production for a few days. A normal person uses up and destroys about 1% of their total blood each day just with normal functioning.

Reticulated, lacy, fenestrated rash of FIFTH disease.If production to replace it shuts off for 5 or even 10 days, that’s only about 5 or 10 percent of the body’s cells and is easily handled by most people until production resumes.

If, on the other hand, a person has any of the blood diseases which cause increased destruction – like Thalassemia, sickle cell disease, leukemia, HIV – “normal” for them may be to loose 10 or even 15% of their red cells per day! To them A few day’s shut off of production is no joke and they may need hospitalization and transfusion before the illness is over. That is called: Aplastic crisis.

There can also be bone marrow suppression as well with the resulting loss of white cells, lymphs and platelets (infection fighters and clotting factors).

Dangers in Pregnancy

The suppression of red cell production occurs everywhere, including in any developing fetus – especially between weeks 14 and 20. That anemia can result in congestive heart failure and what we call “fetal hydrops” and possible fetal demise.

The good news is that this is such a pervasive and contagious organism, over 50% of women in childbearing age have already been infected so have antibodies against getting the disease again; and, less than 10% of those who are infected have fetuses which are affected.

The bad news of course is that it means there is between 1-9% risk of fetal demise when a non-immune pregnant care-giver contracts the disease.

That’s why, even though this seems like such an innocuous and fanciful disease, the diagnoses must be made in a timely fashion so people at risk can be warned and receive medical monitoring as early as possible.

I had one of these patients early in my medical career and his mother lost the baby she was carrying. So, while I’ve seen other physicians seem a bit cavalier about the disease (because, frankly, it IS nearly always quite innocuous) I’ve always asked to see any child with this disease back in the office in 5 to 7 days (or sooner) if only to reinforce the diagnosis and be able to warn and follow-up on any contacts which are at risk.

Other Complications

We began by mentioning that FIFTH disease wasn’t the only expression of the Parvovirus B19. Correlation with various diseases is often quite difficult to prove but some associations are beginning to be found and need further clarification through continued experience.

Associations have been described with encephalitis, neuropathies, myocarditis, nephritis, systemic lupus erythematosus, Henoch-Schönlein purpra and rheumatoid arthritis.

Additionally, it is known to be a cause of chronic anemia in individuals who have AIDS, where it can be frequently overlooked, and it may may trigger an inflammatory reaction in those who have just begun antiretroviral therapy.

And finally, it causes the quite uncommon but distressing: Papular Purpuric Gloves and Socks Syndrome in teenagers and young adults which sort of gives the symptoms that you would imagine from the name.