Cutaneous complications offer ‘lots of mimickers’ for rheumatologic diseases

DESTIN, Fla. — Dermatomyositis and tinea are just two of many dermatologic complications that may resemble rheumatologic conditions, according to a presenter at the 2023 Congress of Clinical Rheumatology-East.

“I am going to focus on cutaneous signs to help differentiate [dermatologic conditions] from rheum mimickers,” Alisa Femia, MD, director of inpatient dermatology at the New York University Grossman School of Medicine at the NYU Langone Medical Center, told attendees.

using Glass.Mapper.Sc.Web.Mvc

She presented several cases and described the myriad interpretations for each.

The first was a morbilliform drug eruption that is more proximal than distal, which has “lots of mimickers,” according to Femia. “This is our most common drug reaction.”

The reaction has no mucosal involvement, is marked by a V-neck or shawl form and can result from immunizations, such ashe shingles vaccine. However, Femia noted that this reaction could also be dermatomyositis.

“Cutaneous dermatomyositis is commonly diagnosed as a drug reaction,” she said. It is crucial for clinicians to determine the etiology of this complication, because if it is immune checkpoint inhibitor-induced dermatomyositis, patients may be at risk for interstitial lung disease (ILD). Morbilliform drug eruptions – or dermatomyositis mimicking as one – may also occur in patients treated with anti-tumor necrosis factor (TNF) therapies.

Another challenging mimic involves drug-induced hypersensitivity syndrome, or as it was formerly known, Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome. This cutaneous manifestation involves a red rash on the face that can spread into nasolabial folds, according to Femia.

“It looks like lupus,” she said. “From a skin perspective, it is different from the morbilliform reaction.”

This syndrome is “a more concerning reaction” that can take approximately 4 weeks to manifest after the patient receives the offending medication. It is a systemic process that can include fever, acute kidney injury and/or hematologic abnormalities, along with elevated liver function tests.

Femia noted that it can resemble dermatomyositis, spongiotic dermatitis or other drug reactions. “We need the help of a full physical examination to differentiate between these entities,” she said. “Biopsy is not always going to bail us out.”

The next complication Femia addressed was Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN), which she described as the “most dreaded reaction” a patient can have to a drug. “This is a horrific, superficial blistering process that usually follows medication by a week,” she said.

SJS/TEN is marked by mucosal denudation and skin pain. “They act like burn patients because they are so critically ill,” Femia said.

Discoid lupus is a common copycat of SJS/TEN, along with Rowell Syndrome; both can be marked by scaling, crusting and dyspigmentation.

Another lupus mimic is MDA5-positive dermatomyositis, according to Femia. “When a patient has ulcerations, it can be misdiagnosed as cutaneous lupus, but it is often MDA5-positive dermatomyositis,” she said. “It is typically amyopathic.”

Rheumatologists, in particular, should also be on the lookout for neutrophilic dermatosis in autoimmune connective tissue disease, which is most often observed in association with SLE. “It typically affects the hands,” she said, noting that this manifestation is often the presenting feature of subsequent systemic disease.

Biopsy of neutrophilic dermatosis will lack vasculitis, Femia noted. In addition to lupus, this complication may also be associated with Schnitzler’s syndrome or adult-onset Still’s disease.

Tinea, or ringworm, is yet another common dermatologic condition that can resemble a number of rheumatologic diseases. “Tinea is one of the greatest mimickers,” Femia said. “It can look like so many things.”

For example, subacute cutaneous lupus may resemble tinea. Femia urged rheumatologists to be careful about using topical steroids in these cases. “Topical steroids will lead to Majocchi’s granuloma, which can be much more challenging to treat,” she said.

Tinea is scaly, Femia added, whereas “granulomatous disorders are not scaly,” she said.

One especially common mimic Femia reviewed was erythema nodosum, which typically presents as a rash on the shin. This rash does not ulcerate and is commonly triggered by oral contraceptive pills, pregnancy, streptococcal infections or IBD.

“Panniculitis can look like erythema nodosum but panniculitis is more above the knee,” Femia said. “Erythema nodosum is not ulcerating.”

Cutaneous polyarteritis nodosa can also look like erythema nodosum, according to Femia. In addition, erythema nodosum may also resemble cutaneous manifestations of ANCA-associated vasculitis.