What Is the Main Idea?
This post is based on the free access article “Diagnostic Accuracy of Trichoscopy in Inflammatory Scalp Diseases: A Systematic Review” published in the journal Dermatology, which looks at how a noninvasive diagnostic technique called trichoscopy can be used to differentiate between dermatological conditions with very similar symptoms. If you have a skin condition that’s affecting your scalp and the diagnosis is proving difficult, this article might be of interest to you and your dermatologist.
What Else Can You Learn?
Read this post to gain some insight into the various diseases that can cause inflammatory reactions on the scalp, including the trichoscopic features that differentiate them.
Why Are Inflammatory Scalp Diseases Difficult to Diagnose?
There are multiple diseases that can cause inflammation and lesions on the scalp. Differentiating between them is not simple, as the lesions and other signs can look similar.
For example, psoriasis, seborrheic dermatitis, contact dermatitis, lichen planopilaris, tinea capitis, discoid lupus erythematosus, pemphigus foliaceus, pemphigus vulgaris, dermatomyositis, and syphilis all cause erythematous patches and scaling.
Erythematous patches are red or purple rashes, often raised or circular, sometimes with small blisters in them. They occur due to injured or inflamed blood capillaries. Scaling means that the outer layers of the skin are coming off in large, scale-like flakes. Scaling often has a dry appearance and can be white or red.
Since the macroscopic appearance is so similar between many diseases, differential diagnosis can be very challenging. There are plenty of methods that help, but many involve taking biopsies or performing other tests that may be uncomfortable for the patient.
What Is Trichoscopy?
Trichoscopy is a noninvasive diagnostic method that can be done by a dermatologist in their office. It is based on dermatoscopy, which involves an instrument that shines a special light on the skin and has a magnifying lens. In trichoscopy, hair and scalp structures may be visualized at many-fold magnification. The trichoscopic instruments can give 10- to 70-fold magnification of hair and scalp structures.
It is widely used for diagnosing the reasons for hair loss but recently, there has been a lot of interest in using it to diagnose inflammatory scalp diseases. In particular, medical researchers hope that it can be used to differentiate between conditions with very similar presentations.
How Does Trichoscopy Help?
Because trichoscopy looks at close magnification of the skin, it can reveal subtle features that are not visible to the naked eye. For example, the scaling might appear continuous but on closer examination, it might be patchy. There might be a pattern to the redness on the skin. When these features appear consistently for a particular disease and are different for other diseases, then they can be considered suitable for differential diagnosis.
What Does the Article Say?
As its name suggests, the article “Diagnostic Accuracy of Trichoscopy in Inflammatory Scalp Diseases: A Systematic Review” is based on a systematic review. That means the authors searched for studies describing the frequency of trichoscopic features related to inflammatory scalp conditions and analyzed the accuracy of using these features in differential diagnosis. They found 58 studies that they could include in a qualitative analysis; of those, 57 were suitable for quantitative analysis.
The qualitative analysis involved reading the descriptions of the trichoscopic features in the papers and case reports to find common and differentiating ones across the diseases. The quantitative analysis involved calculating some diagnostic parameters based on the frequency of the feature appearing for that disease.
The authors’ systematic review indicates that trichoscopy can be used as an accessory tool in the differential diagnosis of inflammatory scalp diseases. They list the trichoscopic features that have the highest specificity for each disease. These are described below along with some information about each disease.
What Is Psoriasis?
Psoriasis is an autoimmune disease that causes abnormal, excessive, and rapid growth of the epidermal (outermost) layer of the skin. This usually causes red patches with white scales on top, but there are forms of psoriasis that cause blisters and changes to the nail pits and nail color. There are many treatment options that focus on managing the symptoms, but there is no cure. The most specific trichoscopic features for scalp psoriasis are diffuse and patchy scaling and simple red loops.
What Is Seborrheic Dermatitis?
Seborrheic dermatitis is also a long-term skin condition that causes red, scaly, and inflamed skin. The areas of the skin with a lot of oil-producing glands are most commonly affected, especially the scalp, but it can also occur on the face, chest, and upper back. Its cause is unknown but there are a number of medications that are able to reduce the symptoms. The most specific trichoscopic features for seborrheic dermatitis are comma vessels (slightly curved blood vessels like a comma) and perifollicular pigmentation (skin color changes around the follicles).
What Is Contact Dermatitis?
Contact dermatitis is an inflammation of the skin that is usually due to the skin being exposed to chemical, physical, allergenic, or other irritants. For example, exposure to turpentine, alcohol, kerosine or drain cleaners can cause chemical irritant contact dermatitis. Poison ivy, poison sumac and poison oak cause allergic contact dermatitis. Nickel in jewelry can also cause allergic contact dermatitis. Treatment depends on the cause. Again, the appearance can be dry skin, red rashes, bumps, blisters and swelling, so it is very similar to the other diseases on this list. The most specific trichoscopic features for contact dermatitis are twisted red loops.
What Is Lichen Planopilaris?
Lichen planopilaris, or lichen planus, is a chronic inflammatory disease with a relationship to the immune system. There are many different forms, including ones that affect the mucous membranes, but the types that commonly affect the scalp have similar red or purple patches with a fine, white scaling over the top. Treatments are rarely effective and there is no cure. The most specific trichoscopic features for lichen planopilaris are milky red areas and fibrotic patches (excessive scarring).
What Is Discoid Lupus Erythematosus?
Discoid lupus erythematosus is an autoimmune disorder that presents as scaling or crusty disc-shaped patches of inflamed skin that are often red. They can cause scarring because they can last a long time, especially if they are not treated. If a patient has discoid lupus erythematosus, they should avoid exposure to sunlight as it brings on the lesions. Steroids can be used to treat existing lesions and a special sunscreen can protect against new ones. The most specific trichoscopic features for discoid lupus erythematosus are follicular plugs (oil from the sebaceous glands trapped around the follicles) and erythema (red rashes) encircling follicles.
What Is Pemphigus Foliaceus?
Pemphigus foliaceus is a generally benign autoimmune skin disorder that presents as blisters, particularly ones that appear when the skin is rubbed. It can be managed quite well but there is no cure. The most specific trichoscopic features for pemphigus foliaceus are scaling in the form of white polygonal structures and serpentine vessels (blood vessels that look like snakes).
What Is Pemphigus Vulgaris?
Pemphigus vulgaris is also an autoimmune disorder that presents as blistering of the skin. It differs from pemphigus foliaceus because it also affects the mucous membranes and can erode the skin to a greater degree. It is rare and more serious, potentially life-threatening. As with most of these conditions, there is no cure but steroids and immunosuppressants can keep it under control. The most specific trichoscopic features for pemphigus vulgaris are red dots with whitish haloes and lace-like vessels (blood vessels that look like lace).
What Is Dermatomyositis?
Dermatomyositis causes skin rashes and muscle inflammation. It is considered a muscle disease and it can be life-threatening. It might be an autoimmune disorder, although this has not been established. The skin symptoms are not the most important aspect of the disease. It cannot be cured, but comprehensive treatment involving steroids, immunosuppressants, heat therapy, physiotherapy and rest is essential. The most specific trichoscopic features for dermatomyositis are lake-like vascular structures, which look like dark blue patches on the skin.
What Is Syphilis?
Syphilis is a sexually transmitted bacterial infection, although it can also be spread by contact with an infected sore on the skin or by sharing intimate items like a razor or a toothbrush with an infected person. It is cured with antibiotics. However, if it causes damage to the body during its course, this might be permanent. If it runs past its primary phase, it can cause a patchy or diffuse set of lesions on the scalp. The article doesn’t define a clear differential diagnostic feature for syphilis that can be found with trichoscopy.
Why Would Your Dermatologist Be Interested in This Article?
Naturally, any dermatologist would be interested in techniques that allow them to perform differential diagnoses without invasive biopsies. Even though the article states trichoscopy can be used as an accessory tool rather than a primary tool, it’s still of great importance that such techniques are developed further.