What Is A Morbilliform Rash?
A morbilliform rash is not a disease. It is not always a symptom of a disease, although in most cases it is. It is best defined as a category, or a description. It is a description of a rash than can occur on a person for one of several reasons, some of which have nothing to do with an illness. Literally, morbilliform means “measles-like”, so a morbilliform rash is a measles-like rash. One could question whether an actual measles rash is or is not a morbilliform rash, since morbilliform means “measles-like”. That however, would be splitting hairs. A measles rash also falls under the umbrella of a morbilliform rash.
A Maculopapular Rash - Besides being “measles like”, a morbilliform rash is categorized as a maculopapular rash that usually covers most of the body. A maculopapular rash is a rash that is characterized by a lesion that is flat and generally rather round, the definition of a macule, and is at the same time somewhat solid, and raised slightly above the surrounding skin, the definition of a papule. The rash then consists of round, solid, flat, but slightly raised spots, which cover the body. The spots by the way are generally less than a centimeter in diameter. If they are larger, they are referred to as patches.
Medication Can Be A Cause - This type of a rash is quite often caused by a virus, the measles virus being a prime example, but in other cases the rash is caused by a non-specific virus, non-specific meaning the virus in question cannot, or has not, been identified. When attempting to determine an underlying disease that may be causing the rash, a diagnosis can sometimes be misleading, as certain drugs and medications can also cause the rash to develop. The disease or disorder in question may not even have a rash as one of its symptoms. Amoxicillin is a drug that is known to have caused this type of a rash in a significant number of those who have taken it. HIV is not known to cause a morbilliform rash, but such a rash can sometimes develop when an HIV patient is treated with sulfa drugs.
Since this type of a rash can be caused by a virus, by bacteria, or by medication, there is no single treatment available. Either the underlying cause must be determined, or treatment would have to be based on a best-guess diagnosis, a path most of those in the medical profession are understandably reluctant to follow. There have been instances when a rash has been treated as if it were caused by a bacteria, when it was actually cause by a virus. In such cases, the treatment in some instances made the rash even more severe.
A Lack Of Specificity - Making matters even more complicated is the fact that while the term morbilliform is somewhat specific, i.e., “measles-like”, the rash itself is a maculopapular rash, a somewhat lengthy name which is not all that specific. Even the term rash isn't at all specific once you think about it. No matter what term you use, it's a little hard to get beyond “measles-like” and most rashes of a morbilliform nature have little to do with measles. Two synonyms that are sometime used in medical circles are exanthematous eruption, and morbilliform eruption. While descriptive, these terms still are not terribly specific.
There seems to be plenty we don't know about this type of a rash, but what is it we do know, or at least can find out in hopes of determining its underlying cause? The age and gender of the affected person can be of importance, as can the knowledge of what medications are being taken. Known allergies, and in some instances, family history can also be important bits of information. Age is a factor, as when such a rash occurs in adults, it tends to be drug or medicine related, and when it occurs in children, the cause is most often a virus. If a rash is acute, rather than chronic, it often can be traced to a specific trigger. If it is chronic, it may be symptomatic of a systemic disease. A rash that has been present for a period exceeding 8 weeks is considered to be a chronic rash. If the rash is due to a specific trigger, such as an allergen, it will sometimes be localized, rather than covering a large area of the body.
Accompanying Symptoms Are Important - Sometimes, a correct diagnosis can only be made if other symptoms are or have been present. A doctor doing the diagnosis will usually attach great importance to headaches, fever, or any other sign of illness a patient describes. If no other symptoms are obvious, the rash itself likely does not require urgent care, beyond treatment that will relieve itching, or is designed to prevent outbreaks of infection due to scratching. It is worth noting that the vast majority of rashes present no danger, and a morbilliform rash is no exception. The underlying cause of a rash is where danger is apt to lurk, which is why a doctor will pay careful attention to any accompanying symptoms or signs of illness.