Increased awareness of rare diseases such as systemic mastocytosis (SM) is associated with fewer diagnostic delays, which leads to improved patient care and quality of life (QoL), according to findings from a retrospective cohort study published in the Journal of Allergy and Clinical Immunology: Global.
SM is a rare disorder that is reported among approximately 32,000 persons in the United States. Individuals with the disease are frequently misdiagnosed or underdiagnosed because of the nonspecific symptoms associated with the condition and the need for patients to undergo invasive biopsies.
Patients with SM often experience debilitating symptoms, such as itching, hives, abdominal pain, nausea/vomiting, diarrhea, depression, brain fog, osteoporosis, bone/muscle pain, and life-threatening anaphylaxis. Such symptoms are reported among individuals with all types of SM, including indolent SM (ISM)—the most common form of the disease—and advanced SM. The advanced type of SM can be divided further into the following forms of the disease:
- SM with associated hematologic neoplasm (SM-AHN)
- Aggressive SM (ASM)
- Mast cell leukemia (MCL)
Recognizing that the risk for progression from ISM to more advanced types of SM presents a challenge, the researchers sought to retrospectively identify, characterize and classify the natural history of individuals with SM. Rates of disease progression were determined, along with utilization of health care resources, referral patterns and time to diagnosis.
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The investigators theorized that the large-scale, patient-level information available within the very detailed medical record system of Kaiser Permanente Southern California (KPSC)—one of the largest Health Maintenance Organizations in the United States—might permit them to establish an approach to diagnosis and health care resource utilization in a sizable cohort of individuals with SM in a real-world setting.
SM is driven predominantly by a gain-of-function mutation (ie, D816V) in the c-KIT gene. The D816V mutation is an activating mutation that can be detected in bone marrow biopsies and in peripheral blood. World Health Organization (WHO) criteria were used to identify patients with confirmed SM from KPSC records.
A total of 116 individuals fulfilled the WHO criteria for SM. Forms of SM reported among the cohort were as follows:
- ISM: 77% of patients
- SM-AHN: 12% of patients
- ASM: 9% of patients
- Smoldering SM (SSM): 2% of patients
- MCL: 0% of patients
Results of the study revealed that five participants initially were misclassified with a less advanced subtype of SM, and three individuals were completely undiagnosed. The average delay to an SM diagnosis was 58.3±73.1 months.
Overall, 18% of participants progressed from a nonadvanced type of SM—that is, ISM or SSM—to advanced SM over an average of 88.3±82.7 months.
Individuals with SM incurred higher rates of healthcare resource utilization post-diagnosis compared with pre-diagnosis. These increased rates included rises in urgent care visits, emergency department visits, specialty provider visits and hospitalizations.
“Prospective studies are needed to better characterize this patient population . . . and [the] follow-up [that] is needed to recognize advanced forms of SM in order to implement appropriate treatment,” the authors concluded.
