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Dermatology in SM care
The Dermatologist’s Role in SM Care: Expert Answers to Your Frequently Asked Questions

Released: May 04, 2026

Lauren M. Madigan
Lauren M. Madigan, MD
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Key Takeaways
  • Fixed skin lesions in adults are highly suggestive of SM, as more than 90% of patients meet the diagnostic criteria, and further staging is warranted.
  • A confirmed SM diagnosis generally includes skin biopsy, complete blood count, metabolic panel, serum tryptase, and highly sensitive KIT D816V testing.
  • Early referral to allergy, immunology, hematology, or a Center of Excellence can improve disease staging and access to multidisciplinary care and novel therapies for patients with SM and significant symptom burden.

In this commentary, Lauren M. Madigan, MD, answers questions posed by healthcare professionals (HCPs) during a live webinar titled “Expert Conversations in Systemic Mastocytosis: Ask an Expert” held in April 2026. Learn best practices for identifying patients with systemic mastocytosis (SM), including the symptoms and red flags that warrant referral to other specialties, as well as specific treatment and monitoring considerations for dermatology HCPs.

What are some clinical clues that distinguish mastocytosis from common dermatologic disorders like eczema, urticaria, and postinflammatory hyperpigmentation?
Adults with SM may present with flushing, itching, and fixed skin lesions. The latter typically follows the pattern of monomorphic maculopapular cutaneous mastocytosis, comprised of small (usually 2-4 mm), uniform, red/brown macules and papules distributed across the patients’ trunk and proximal extremities. Of note, lesion count can differ significantly among patients, with some exhibiting less than a dozen while others have near diffuse involvement with confluence of individual lesions.

One important clinical clue is the presence or absence of a Darier’s sign. HCPs can perform this bedside test by taking a tongue depressor and stroking a lesion 5 times with moderate pressure. In my practice, I also stroke the unaffected surrounding skin to help exclude dermatographism. With mastocytosis in the skin, erythema and edema will develop within several minutes, which is not seen in the unaffected skin. This is considered a positive Darier’s sign and is consistent with mastocytosis.

It can also be helpful to perform a skin biopsy when confirming a diagnosis. In doing so, HCPs should indicate to the dermatopathologist a concern for mastocytosis, which will help direct additional staining and evaluation. Sending biopsies to a center with a high case volume/expertise in interpreting mastocytosis can also increase sensitivity.

At what point should HCPs refer patients to allergy, immunology, hematology, or a specialized SM center? And what should the first workup for suspected SM look like before referral?
My initial workup for mastocytosis in the skin in the adult population includes a lesional skin biopsy, a complete blood count with differential, a complete metabolic profile, a serum tryptase level, and KIT D816V mutational analysis. I do the latter via a highly sensitive technique such as digital droplet PCR, as next-generation sequencing may miss patients with a low variant allele fraction.

If a community HCP is not familiar with ordering these laboratory studies, they can refer patients to a specialist simply based on a positive skin biopsy, as most adults with fixed skin lesions are going to meet the diagnostic criteria for SM. Similarly, all patients should at least have a discussion with their HCP regarding complete staging, including a bone marrow biopsy, as staging allows patients to be classified accurately and provides access to the newer targeted therapeutics.

If you do not have SM specialists—whether in allergy/immunology or hematology—in your area, there are many Centers of Excellence and Reference Centers across the US. The American Initiative in Mast Cell Disorders (or AIM) provides a comprehensive list of these centers on its website. The benefit of referring patients to a Center of Excellence is that these centers provide multidisciplinary care, have experienced pathologists to interpret additional studies, and provide access to active, on-site clinical trials.

For patients with SM and cutaneous symptoms, what therapies do you use in the first-line setting?
For first-line therapy in patients with indolent SM (the most common type of SM), HCPs should continue to utilize supportive agents, such as second-generation antihistamines, to help patients manage their symptoms. Additional treatment options include cromolyn sodium, leukotriene receptor antagonists, proton pump inhibitors, and omalizumab. Venom immunotherapy may also be considered for appropriate patients to prevent anaphylaxis.

Phototherapy may be considered for patients with symptomatic skin lesions, but HCPs should remain thoughtful about the total cumulative UV exposure and intended endpoint with this treatment.

Although these interventions are effective for many patients, others may have persistent and debilitating symptoms despite the best available supportive therapies, resulting in a significant impact on their quality of life. For these patients, HCPs should consider targeted therapy, including selective inhibitors of D816V-mutated KIT such as avapritinib.

How do you help patients with SM balance their trigger avoidance?
Not all patients are going to have the same triggers, so HCPs should work with them individually to determine what their specific risks are. Obviously, it is vital to recognize Hymenoptera anaphylaxis and refer these patients to allergy/immunology for consideration of venom immunotherapy. In addition, HCPs should counsel patients about perioperative anesthetics and ensure that patients and their surgical teams know about the potential risks. Patients with food sensitivities or environmental allergies should also be referred to allergy for more specific testing and guidance, while those with physical triggers, such as heat and friction, can try to mitigate these where possible.

How early should HCPs refer patients for bone health assessment?
I generally refer my adult patients for a DEXA scan at the time of their diagnosis, and my institution has a wonderful endocrinologist who specializes in bone disease and SM. We have seen patients develop fractures at an early age, and this is something HCPs must identify early and manage.

As seen at your institution, what are some common reasons why SM gets misdiagnosed?
In patients with subtle or sparse skin lesions, mastocytosis can be mistaken for benign skin lesions such as solar lentigines (“sunspots”). Others are identified as having mastocytosis in the skin, but the initial HCP failed to recognize the association with systemic disease. Others, perhaps, are told their serum tryptase level is <20 ng/mL and that they do not need to worry about systemic disease in this setting, which we know to be false.

Another reason SM can get missed is if the dermatopathologist or hematopathologist interpreting biopsy samples is unfamiliar with the disease, as findings can be subtle and the diagnosis often requires experience. I am very fortunate that within our Center of Excellence, we have exceptional pathologists in dermatology and hematology with specific expertise in SM.

Then there are patients who do not have fixed skin lesions. As many other SM symptoms are relatively nonspecific, such as flushing, abdominal pain, diarrhea, and fatigue, patients can get diagnosed with more common disorders like gastroesophageal reflux disease or irritable bowel syndrome prior to it being recognized as SM.

For patients who achieve disease control with treatment, what do you monitor in follow-up?
As HCPs, it is important to ask questions to identify any potential adverse events and to ensure adequate disease control with any form of treatment. We regularly monitor labs in our SM patient population, including serum tryptase, KITD816V variant allele fraction, CBC, and CMP, assessing for trends over time.

As a dermatologist, I like to offer my expertise with regard to full skin examinations, both to assess for treatment response and also to detect additional pathology. If you can imagine, some of these patients have hundreds of fixed skin lesions, making it challenging to identify skin cancers, given how “busy” their skin can be without an experienced eye.

Your Thoughts
How often do you consider SM in your patients presenting with maculopapular lesions? You can get involved in the conversation by answering the poll question and posting a comment below.

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