Experts Discuss the Skin Manifestation of Rheumatic Disease 

Rheumatologists frequently treat diseases with skin involvement despite having limited training focusing on the skin. Further, many rheumatologists cannot recognize rheumatic disease on darker pigmented skin.

These gaps were addressed in More Than Skin Deep: What Rheumatologists Should Know About the Skin, on Saturday, Nov. 15. The session will be available on-demand to all registered ACR Convergence 2024 participants after the meeting through Oct. 10, 2025, by logging into the meeting website.

Ginette A. Okoye, MD, FAAD, Professor and Chair of Dermatology at Howard University College of Medicine, discussed how rheumatic disease appears in patients of color.

Generally, the structure and function of the skin is the same in all races. However, there are some important differences, including pigmentation. Skin color is determined by the number of melanosomes within a melanocyte and within epidermal cells, as well as the size of those melanosomes, the type of melanin they contain, and how they are distributed throughout the epidermis.

“In people with darker skin, they tend to have larger, more numerous melanosomes, more eumelanin than pheomelanin, and they tend to be distributed throughout the entire epidermis from the stratum corneum all the way down to the basal layer,” said Dr. Okoye.

She described melanin as a double-edged sword. Melanin provides protection from skin cancer, yet it also may be absorbing the thing that might be causing cellular damage and reactive oxygen species. Further, melanin can mask erythema and contribute to fibrosis.

“Melanin can mask redness, and we’re taught to look for redness when we’re trying to diagnose skin conditions. So, if melanin is masking that, that can lead to delayed diagnosis,” Dr. Okoye explained. 

In skin of color, erythema can be red, purple, dark brown, and blue-black. To aid in identifying erythema, Dr. Okoye recommends putting a blue background on a photo of the area in question. This technique can help the redness stand out. She also noted that cameras may better detect redness than the human eye.

Dr. Okoye also stressed that changes in pigmentation, especially the loss of pigmentation, may be a clinical marker for fibrosis and scarring.

Laura Hummers, MD, ScM, Co-Director of the Johns Hopkins Scleroderma Center, discussed the differences in the clinical manifestation of scleroderma and its mimics, and the appropriate treatment for each condition.

“Most of these diagnoses are clinically distinguishable without biopsy if you just think about some of these things,” Dr. Hummers said. “One is the distribution of skin tightness, and the quality of the tightness of the skin is probably the second most important thing. This is hard to capture in a lecture, but when I have fellows in my clinic, we spend a lot of time talking about the characteristics of the quality of the skin. Does it feel doughy? Does it feel thick? Is there a papular component to it? And then think about the depth of the skin.”

As general advice, if the skin manifestation spares the fingers or prominently involves the back, the clinician should think of a scleroderma mimic. If generalized morphea is seen, the clinician should think about coexisting eosinophilic fasciitis. When distal leg thickness is present, it may indicate morphea and lipodermatosclerosis.

In some cases, a biopsy may be needed to differentiate scleroderma and its mimics. The depth of the biopsy should be based on clinical exam and differential diagnosis. Mucin staining may be needed to differentiate some of the mimics of scleroderma.

When monitoring patients with limited skin findings, it is important to examine their phenotype. High-risk features include early disease, Scl-70 or RNA polymerase III (Pol III) positivity, skin changes beyond the fingers, and joint involvement. These patients should be observed at short intervals if treatment is not started. Upon evidence of progression, they should receive treatment. Low-risk features include puffy fingers, centromere positivity, and stable skin findings. These patients do not usually require therapy and are at low risk of progression.