It is now more possible than ever for us to characterize the life experience of an individual with a chronic or incurable disease—understanding the complications that may arise along the way, when they may arise, and the best evidence-based methods to address them. 

In recent years, increased funding has flowed into research that stretches over years; in other words, research that seeks to understand the impact of a drug/treatment over a long period of time.

Alternately, some researchers conduct studies at their centers for years studying the clinical outcomes of patients with a particular disease. This kind of research allows clinicians to anticipate needs and focus on producing therapies where they are most needed. 

Omalizumab Use for Four Years 

In Federal Practitioner, Weiss and colleagues presented the case study of a patient with indolent systemic mastocytosis treated with omalizumab over a 4-year period.

A 32-year-old woman presented due to recurrent episodes of anaphylaxis, occurring 1 to 2 times a month. She also has a chronic skin rash that had progressively worsened over the previous 5 years. 

Read more about systemic mastocytosis etiology 

Her physicians initially misdiagnosed her with idiopathic anaphylaxis. She later returned multiple times for vaso-vagal syncope, unexplained allergies, dizziness, and shortness of breath. This time, her physicians diagnosed her with idiopathic urticaria. 

A closer history-taking revealed that these symptoms were often accompanied by mild facial angioedema, acute sinus pressure, tachycardia, vomiting, and lightheadedness. Her blood pressure had systolic readings in the 80s. The patient began to develop nonpruritic freckles on her chest, which eventually involved her trunk and extremities. 

Finally, a bone marrow biopsy was obtained, revealing multiple infiltrates of monomorphic, spindled, CD117-positive, CD2-positive, and CD25-positive mast cells. These mast cells were arranged interstitially and paratrabecular and were associated with reticulin fibrosis. Her physicians diagnosed her with indolent systemic mastocytosis according to World Health Organization guidelines. 

Her physicians initially prescribed her maximal antihistamine and antileukotriene therapy, which failed to resolve her symptoms. She was subsequently prescribed omalizumab (300 mg subcutaneous injection once every 4 weeks), and has continued to be on this therapy for 4 years, having only experienced 1 anaphylactic episode during that time. Her cutaneous symptoms also significantly improved. 

“At the time this article was written, our patient had now 52 months of continuous treatment without any adverse reactions noted, suggesting the treatment’s long-term efficacy,” the authors of the study wrote. 

A 15-Year Single-Center Study 

Another long-term study of systemic mastocytosis was conducted by Ungerstedt and colleagues at the Center of Excellence for Systemic Mastocytosis at the Karolinska Institute in Sweden. The study was published in Cancers.

Since the center’s establishment in 2006, a total of 349 consecutive adult patients have been referred for clinically suspected mastocytosis. All suspected cases were thoroughly examined with both a clinical and a physical workup, together with routine laboratory investigations. 

“Patients with a confirmed [systemic mastocytosis] diagnosis underwent routine investigations, including ultrasound or computerized tomography of the abdomen to detect B- and C-findings and to diagnose advanced variants of [systemic mastocytosis], and their bone mineral density was measured by dual X-ray absorptiometry at the lumbar spine and proximal hip to identify patients with bone involvement,” the authors of the study wrote. 

A total of 195 patients consented to participate in this 15-year retrospective study (from 2006 to 2020), which had the primary aim of understanding the ways in which patients present to the center, as well as uncovering ways to improve the diagnostic and follow-up processes. The median follow-up period was 7.5 years.

The researchers reported that the overwhelming majority (88.2%) of participants had the indolent form of systemic mastocytosis, and none progressed to advanced systemic mastocytosis. In addition, the median time from the first patient-reported symptoms to diagnosis was 10 years. They estimated that the prevalence of systemic mastocytosis among adults in Stockholm was 10.6 per 100,000 inhabitants and that the mean incidence of new diagnoses in the same region was 0.77 per 100,000 people. 

The research team also reported that 18 patients had some form of solid tumors; 5 had cutaneous melanoma, 4 had breast cancer, 4 had gastrointestinal malignancies, and 2 each had pancreatic cancer and small-cell lung cancer. 

Read more about systemic mastocytosis treatment 

“The present study summarizes our 15 years of experience of [systemic mastocytosis], and underlines the need for standardized algorithms for diagnostic workup, risk stratification, and treatment,” the authors of the study wrote. 

It is only by collecting data over a relatively long period of time that useful information concerning epidemiology, treatment outcomes, and complications can come to light. Overall, both of these studies suggest that a heavy disease burden is still attached to a diagnosis of systemic mastocytosis, even in dedicated treatment centers. 

So what is the best way forward? Certainly, long-term clinical studies are as needed as ever before to ensure that each step taken by the medical community is illuminated by the very best evidence. Until then, clinicians should focus on early diagnosis and the early initiation of treatment to improve outcomes. 


Weiss SL, Hyman JB, Carlson GS, Coop CA. Long-term successful treatment of indolent systemic mastocytosis with omalizumabFed Pract. 2021;38(1):44-48. doi:10.12788/fp.0081

Ungerstedt J, Ljung C, Klimkowska M, Gülen T. Clinical outcomes of adults with systemic mastocytosis: a 15-year multidisciplinary experienceCancers (Basel). 2022;14(16):3942. doi:10.3390/cancers14163942