A Closer Look at Scalp Dermatomyositis

Scalp Dermatomyositis is a Potential Mimicker of the Red Scaly Scalp in Women

Dermatomyositis is a autoimmune disease that has both skin and muscle symptoms. A wide variety of skin manifestations are knowing to exist. The disease has many systemic symptoms beyond the skin and muscles including lungs, heart and gastrointestinal systems. In addition, 20-30 % of patients with dermatomyositis will develop a cancer.

The exact incidence of dermatomyositis is not clear but anywhere from 1:50,000 to 1:100,000 people are diagnosed with dermatomyositis each year. It affects children and adults and women are 2-3 times more likely to be affected than males.

I took note of a new study published in the Dermatology Online Journal. Here, the authors set out to evaluate all patients 18 years and over with dermatomyositis seen at UC Davis in Sacramento 2011-2021. They identified 156 individuals. Mean age was 58.9 and 2/3 were female.

Skin Findings and Sings

A variety of skin findings were documented by the authors. 50.6 % had Gottron papules. 29.5 % had nailfold changes. Heliotrope rash (around the eyes) was noted in 28.8%. V-sign was present in 26.9 %. Shawl sign in 23.1 %. Mechanic’s hands were present in 7.7% and calcinosis cutis was present in 1.9 %

Scalp Findings in Dermatomyositis

Scalp dermatomyositis was present in 12.8 %.

Muscle Involvement in Dermatomyositis

35.9% of the patients were “clinically amyopathic” meaning they did not appear to have any muscle involvement at the time of clinical examination in the office setting. However, 37.5% of these clinically amyopathic patients actually had evidence of muscle involvement when muscle enzymes, EMG or MRI was performed.

Ck was elevated in 50.4 % with average value of 2503. Aldolase was elevated in 37.7 % with mean value of 21.3. AST was elevated in 25.2 % with mean 142 and ALT was elevated in 19.3 % with mean 130.

Malignancy in Dermatomyositis

In this study, 22.4 % of patients had a malignancy.

Systemic Involvement

25 % had lung involvement (generally interstitial lung disease). African American and Black patients were five times more likely to have lung involvement that white patients. 15 % had dysphagia and 4 % had cardiac involvement. 25 % had depression.

Comment

I always pay attention to studies that draw attention to the topic of scalp dermatomyositis. Scalp dermatomyositis is probably quite a bit underdiagnosed. It can mimic seborrheic dermatitis and psoriasis quite closely and so one needs to have this diagnosis in the back of their minds at all times especially in women 50-70 with scaly red scalps.

A full skin examination is needed to confidently diagnosis dermatomyositis. There are many skin findings that researchers and clinician have identified over the years. These include the famous Gottron papules, Gottron sign, shawl sign, V sign and heliotrope rash. Every dermatology trainee learns about these skin signs. This study here reminds us that not all patients with dermatomyositis have these findings.

What particularly caught my attention in this study was the low proportion of patients with dermatomyositis that have scalp involvement. In many studies the proportion of patients with dermatomyositis who have scalp involvement is in the range of 60-80 %. Those numbers comes once a scalp is examined in full. What we don’t know in this retrospective review is whether the scalp was examined, and whether it was examined with trichoscopy and how exactly it was examined. In dermatomyositis, it’s common to examine the skin, face and hands and forget the scalp. This study just summarizes patient charts over many years.

Trichoscopy is powerfully helpful in dermatomyositis. When I think scalp dermatomyosis (SDM) I immediately think SVP (as in sil vous plait). It helps me remember to think about scaling, vessels and pigmentation. These are the key features of trichoscopy of SDM. SDM has scaling around hairs and between hairs. SDM as blood vessels that are serpentine, bushy and blotchy like lakes. DSM has pigmentation around hairs and also between hairs.

Scalp dermatomyositis at first looks like lichen planopilaris or dandruff or folliculitis decalvans under trichoscopic examination because of the perifollicular scale and tubular scaling (sometimes compounding) but it often just doesn’t seem to be convincingly scarring. My mind notes the scaling and then wonders why this scaling hasn’t caused more hair loss in this patient. What stands out with trichoscopy is that red blobs that can be seen - as though someone’s red pen leaks on the scalp. These are the red lake-like structures.

Red lake like structures are highly specific for scalp dermatomyositis and together with “snaky” vessels, perifollicular scale and tubular scaling (that looks like a mix between lichen planopilaris and folliculitis decalvans) one can have a good idea that scalp dermatomyositis might be a diagnosis. Red lake like structures are not seen all that often but when they are they are highly specific for scalp dermatomyositis.

Scalp Dermatomyositis needs to be considered in all patients 50 and over with scalp itching, burning and symptoms together with redness. Scalp dermatomyositis does not always give hair loss but about 30-40 % of the time it does. The scalp symptoms can be troublesome to patients. So the diagnosis of scalp DM must be given careful consideration in patients with scalp symptoms that just aren’t responding well to treatment.

Scalp DM tends to occur mainly in women and scalp involvement makes it less likely to have associated malignancy - at least in one study by Tilstra and colleagues.

Scalp DM is challenging to treat - and more challenging than LPP. Topical steroids, steroid injections and hydroxychloroquine (Plaquneil) are often tried first but much of the time other immunosuppressive like mycophenolate mofetil or methotrexate are needed.

REFERENCE

Engel et al. Characteristics of patients with dermatomyositis from 2011-2021 at a tertiary care center. Dermatol Online J . 2021 Nov 15;27(11).

Tilstra J et al. Scalp dermatomyositis revisited. Arch Dermatol . 2009 Sep;145(9):1062-

Kasteler JS and Callen JP. Scalp involvement in dermatomyositis. Often overlooked or misdiagnosed.JAMA. 1994 Dec 28;272(24):1939-41.