What are the other Names for this Condition? (Also known as/Synonyms)

• Drug-Induced Dermopathy
• Medication-Induced Dermatomyositis
• Pseudo-Dermatomyositis

What is Drug-Induced Dermatomyositis? (Definition/Background Information)

• Dermatomyositis is a rare inflammatory condition of unknown cause, which results in a characteristic skin rash as well as muscle weakness. It is a progressive condition that usually worsens over time
• Drug-Induced Dermatomyositis occurs secondary to the use of certain medication, as an adverse reaction of the body to the drugs. The common medication causing the condition include hydroxyurea; it is reported that nearly 4% of the individuals on this medication may develop dermatomyositis
• Stopping or discontinuing the use of such medications may decrease progression of Drug-Induced Dermatomyositis and/or may result in resolution of the condition. With adequate treatment, including a stoppage of the offending medication, the outcomes are good

Who gets Drug-Induced Dermatomyositis? (Age and Sex Distribution)

• Individuals of all ages may be affected by Drug-Induced Dermatomyositis, although most cases are noted in adults. The condition is uncommon in children
• Both males and females are equally affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Drug-Induced Dermatomyositis? (Predisposing Factors)

The key risk factor for Drug-Induced Dermatomyositis is the use of certain medications that cause the condition as a side effect. The following class of medications have been implicated:

• Administration of hydroxyurea for chronic cases myeloproliferative disorders - around 50% of Drug-Induced Dermatomyositis cases are due to this factor
• Anticonvulsant medication
• Antirheumatic medication such as penicillamine
• BCG vaccination
• Cholesterol-lowering drugs, such as statins, which work by inhibiting the HMG-CoA reductase pathway
• Cyclophosphamide
• Non-steroidal anti-inflammatory drugs (NSAIDs)

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Drug-Induced Dermatomyositis? (Etiology)

Currently, the definitive cause of dermatomyositis is unknown. Research experts believe that it may be caused by a viral infection affecting the muscles or occur from immune system dysfunction.

• Drug-Induced Dermatomyositis develops from the use of certain medications/drugs that are administered for various health conditions. It is believed that the offending drug potentially causes an abnormal cell-mediated immune response in the body
• Sometimes, the appearance of signs and symptoms due to the drug may not be observed immediately after starting the medication. The condition may arise after a certain period of time
  • In hydroxyurea-associated dermatomyositis (following long-term therapy), commonly skin signs and symptoms, and rarely, muscle involvement is observed. The symptoms may develop over several years
  • In non-hydroxyurea-associated cases, the signs and symptoms typically develops soon after starting usage of the causative medication, usually within two months. Also, both cutaneous and muscle involvement is noted

What are the Signs and Symptoms of Drug-Induced Dermatomyositis?

The signs and symptoms of Drug-Induced Dermatomyositis may vary from one individual to another. It may also be mild or severe and may be related to the type and usage of the drug. The condition is known to get better after stoppage of the offending medication.

Dermatomyositis commonly involves the skin, muscles, and joints. It may rarely affect other internal organs such as the lungs, heart, and gastrointestinal tract.

The signs and symptoms may include:

• A purplish-reddish, painful, itchy rash (called a heliotrope rash) that develops on the body is observed in most cases. Typical locations are the frontal scalp, upper arms and upper chest
• Dusky violet darkening of the upper eyelids, near the lash margin
• Other forms of skin lesions may be observed, such as Gottron papules on the knuckles, and tiny, dilated, telangiectatic vessels at the nailfolds
• Irregular red-violet skin patches on other sun-exposed areas
• Muscle involvement with muscle pain may be noted
• When the skin presentations are associated with hydroxyurea, the lesions are generally noted on the hands (back side), fingers, and face

How is Drug-Induced Dermatomyositis Diagnosed?

The diagnosis of Drug-Induced Dermatomyositis may be difficult, especially if the individual is on multiple medications and the onset of signs and symptoms are noted following several years after administration of the offending medications. Moreover, other (non-dermatomyositis) side effects of medications may present additional challenges in establishing a diagnosis.

The following tests and exams may be used in the diagnosis of Drug-Induced Dermatomyositis:

• Complete physical examination and thorough medical history evaluation (including current and past medication use)
• Assessment of the presenting signs and symptoms
• Dermoscopy: It is a diagnostic tool where a dermatologist examines the skin using a special magnified lens
• Wood’s lamp examination: In this procedure, the healthcare provider examines the skin using ultraviolet light. It is performed to examine the change in skin pigmentation
• Blood analysis
• Magnetic resonance imaging (MRI) scans to detect muscle abnormalities
• EMG (electromyography), to record electrical impulses that control the muscles
• Skin biopsy: A skin tissue biopsy is performed and sent to a laboratory for a pathological examination. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis
• In complex cases, a muscle biopsy may be needed
• A hallmark of the pattern of muscle involvement leads to easy fatigue of the shoulder and hip muscles. This leads to difficulty in grooming hair or rising from a chair without pushing off with assisting from the arms. Part of the history and exam will focus on these issues

A differential diagnosis may be necessary to eliminate other conditions that present similar signs and symptoms. This may include:

• Fluoroquinolone-induced tendinopathy
• Inclusion body myositis
• Necrotizing myopathy
• Statin myopathy

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Drug-Induced Dermatomyositis?

If Drug-Induced Dermatomyositis is left untreated, it can result in certain complications. Some of the complications include:

• Skin atrophy
• Raynaud phenomenon
• Calcinosis
• Muscle and joint complications
• Emotional stress from cosmetic concerns
• Recurrence/relapse of the condition
• Treatment medication side effects
• Difficulty satisfying work requirements, or staying physically active

How is Drug-Induced Dermatomyositis Treated?

Following a diagnosis of Drug-Induced Dermatomyositis, the treatment provided may include:

• Discontinuing the medication responsible for the side effect, where possible, which may result in a cure, or in improvement of the condition
• Undertaking a treatment of dermatomyositis, especially when the symptoms do not subside following medication discontinuation, through:
  • Topical therapy using corticosteroid creams for the rash
  • Oral Steroid medications which would help the myopathy and the rash
  • Other immunosuppressive therapy, if needed
  • Physical therapy and exercise to aid in mobility (compensation for muscle weakness)

Follow-up care with screening and check-ups are important at regular intervals.

How can Drug-Induced Dermatomyositis be Prevented?

Current medical research has not established a method of preventing Drug-Induced Dermatomyositis. However, the following measures may be considered to help lower one’s risk for the condition:

• Drugs that cause the condition may be discontinued or alternative medication prescribed; nevertheless, this has to be decided by the healthcare expert
• If the use of certain medications places an individual at an elevated risk for this skin condition, it is advisable to check with the physician on the same
• Avoid self-medication or bringing about any changes to one’s medication dosage without consulting the healthcare provider
• Inform your physician if you are allergic to any medication

Periodic monitoring or follow-up of the condition with the healthcare provider is recommended.

What is the Prognosis of Drug-Induced Dermatomyositis? (Outcomes/Resolutions)

The prognosis for Drug-Induced Dermatomyositis is usually good in many cases, upon discontinuation of the medication and adequate treatment of the condition. However, the time for complete resolution may vary from one individual to another.

• In many, an improvement to complete resolution is noted within two months
• In some, it may take about a year for all the symptoms to subside and regress completely

Additional and Relevant Useful Information for Drug-Induced Dermatomyositis:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/healthy-living/skin-disorders/