Morbilliform Drug Eruption - Causes, Symptoms, Diagnosis, and Treatment

Introduction:

A drug reaction that forms an eruption is called a morbilliform drug eruption. Several drugs can cause this reaction, antibiotics being the most common group of drugs that cause the reaction. It can be mistaken for exanthems that are caused by viral and bacterial infections. It is also called maculopapular drug eruption or exanthematous drug eruption.

What Are the Causes of Morbilliform Drug Eruption?

Adverse reactions to drugs are called morbilliform drug eruptions. It is a form of allergic response classified as a type IV immune reaction due to cytotoxic T-cell mediated reactions. Either the drug, metabolic by-product of the drug, or protein content of the drug, can be the cause of the allergic reaction. Inflammation is a cell-mediated type of immunity with the release of cytokines.

Who Are Affected by Morbilliform Drug Eruption?

• About two percent of a new drug prescription can cause a drug eruption. Of all the drug reactions, 95 % are morbilliform drug eruptions.

• The main drugs that cause drug reactions include Penicillins, Cephalosporins, Allopurinol, Sulfonamides, anti-epileptic drugs, and NSAIDs. In addition, some herbal medicines and natural combination therapies are also known to cause drug reactions.

Other risk factors include:

• Underlying viral infections include infectious mononucleosis, Epstein-Barr virus, herpes simplex 6 and 7, and human immunodeficiency virus.

• Cystic fibrosis.

• Autoimmune disorders.

• Strong family history or previous family history of a drug reaction.

What Are the Clinical Features?

• The first time a reaction occurs due to a drug, it appears one to two weeks after commencing the medication. It can also happen even after a week after drug administration.

• On re-exposure, it can appear in one to three days.

• In extremely rare cases, the drug reaction can occur after months or even years.

• It first appears on the trunk and spreads to the limbs and neck. It occurs bilaterally and symmetrically.

• It may be associated with fever and itch.

• Pink to red flat macule or papule forms, which can cause irritation; as the lesion subsides, the redness decreases, and skin on the surface peels off.

• A typical lesion looks like a pinkish-red macule or papule. A papule is a raised lesion, whereas a macule is a term for a flat discoloration on the skin.

• Rash, urticaria (skin rash caused due to food allergy), annular or polymorphous in shape.

• Different lesions can coalesce together to form large red patches.

• Lesions blanch on applying pressure.

• Lesions on lower legs do not blanch on pressure.

• Rash in groin and axilla areas are primarily due to SDRIFE or symmetrical drug-related intertriginous and flexural exanthem.

• However, the axilla, groin, feet, and hands are generally spared.

• In uncomplicated cases, mucous membranes, nails, and hair are unaffected.

What Complications can Morbilliform Drug Eruption Cause?

The difficulty primarily arises in differentiating uncomplicated morbilliform eruptions from serious cutaneous adverse reactions (SCAR). These reactions include:

1. Stevens-Johnson syndrome or toxic epidermal necrolysis (SJS/TEN).

2. Drug hypersensitivity syndrome.

3. Acute generalized exanthematous pustulosis (AGEP).

If a patient has the following symptoms, they should be hospitalized and should be given special care:

• High fever.

• Malaise.

• Erythroderma, which covers the whole body.

• Blisters.

• Tender skin.

• Palpable purpura.

• Pustules (lesions or blisters filled with pus).

• Organ involvement or failure, such as kidneys, liver, and lungs.

How to Diagnose Drug Eruption?

• Drug eruption is primarily based on clinical manifestations such as a typical rash that appears after intake of a drug that was recently introduced.

• To diagnose or identify the cause, a drug calendar is formed, which includes all the prescribed medications and over-the-counter medication, with the starting date of each new drug. This is then compared with the onset of the rash. The calendar should have at least two weeks up to one month of information.

• The drugs are then categorized into likely to be the cause or unlikely to be the cause based on the following:

  • Time of onset of the rash.

  • The drug is based on a history of allergy causation. Drugs that do not have a history of causing allergies are excluded.

  • If a patient has a history of drug reactions, then that drug is the likely cause.

  • There are no specific tests for identifying the drug; it can be confirmed by the elimination of other rash-causing viral disorders such as rubella, measles, scarlet fever, or non-specific redness or erythema such as connective tissue disease, Kawasaki disease, and acute graft-versus-host disease.

• Routine blood tests can be done to identify complications. Tests include:

  • Kidney and liver function tests.

  • Routine blood count.

  • C-reactive protein.

  • A serology test is done for an infection that causes skin rashes.

  • Skin biopsy tests are done to identify interface dermatitis and mixed perivascular infiltration.

• Further investigations can be done if the patient does not improve even after the stoppage of the drug.

How to Treat Morbilliform Drug Eruption?

• The crucial treatment is the stoppage of the drug that causes the reaction. Identifying the causative drug is the primary step. The skin reactions will subside when the drugs are stopped.

• The drugs are discontinued based on the need for the drug and the replacement available. The cost-benefit ratio is analyzed.

• Monitor the patients for complications.

• Steroids can be applied topically, along with emollients, which can improve the rashes.

• Red and inflamed areas of the skin can be wrapped.

• Antihistamines are prescribed, this is so that the allergic reactions subside.

How Can Morbilliform Drug Eruption Be Prevented?

• The reaction can not be prevented, especially since it is not possible to identify without the reaction first occurring. However, recurrent eruptions can be prevented if vigilant.

• Minimizing the prescription of antibiotics that are known for causing drug reactions.

• Medical records should be updated and maintained with previous drug reactions.

• Raising awareness in the patients and educating them regarding the cause of the rash and the possible danger if re-exposed to the same medication.

What Is the Prognosis of Morbilliform Drug Eruption?

Drug eruptions generally have a good prognosis. Once the causative drug is stopped, the rash improves within 48 hours. It completely clears within one to two weeks. In some cases, the rash resolves even without discontinuing the medication. If the drug is continued, the eruption can persist or progress to erythroderma (a condition that can cause a rash on the entire skin surface).

Conclusion:

Adverse reactions to some medications can result in skin rashes called morbilliform drug eruptions. Only two percent of the drug can cause such a reaction. The rashes can be a macule or a papule and can be difficult to identify from viral skin rashes. Stopping the drug can help resolve the skin eruptions, and therefore the condition has a good prognosis.