A new case report published in Revista Médica de Minas Gerais highlights how advanced systemic mastocytosis (SM) can be difficult to recognize when it develops with gastrointestinal (GI) distress and no skin symptoms.
The case report describes a 78-year-old woman whose only major symptoms were chronic diarrhea, anemia and weight loss. After two years of various tests that failed to identify a cause, specialized testing ultimately revealed advanced SMAdvanced SM In these subtypes of SM, mast cells begin to damage organs. Advanced SM includes the subtypes aggressive SM, mast cell leukemia and SM with an associated hematological neoplasm..
SM most commonly affects the skin, bone marrow and internal organs. Skin symptoms such as flushing, itching and rashes are seen in most patients, while gastrointestinal symptoms can also occur because mast cells release inflammatory substances that affect the digestive tract. But GI symptoms alone are uncommon.
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In this case, the woman underwent extensive gastrointestinal testing, including endoscopy and multiple colonoscopies. Doctors found only a small hiatal hernia and diverticular disease, with no explanation for her persistent diarrhea or anemia. Imaging studies also failed to reveal a cause.
Further evaluation by a hematology team showed a serum tryptaseTryptase A protein enzyme that is primarily produced by mast cells and stored in small pockets within the cells, known as granules. High levels of tryptase are a key indicator of SM. level above 200 µg/L. A bone marrow biopsyBone marrow biopsy A procedure to collect a sample of bone marrow using a needle. Often used to examine the characteristics of mast cells and diagnose SM. demonstrated dense mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. infiltration, while immunohistochemical testing was positive for CD25, c-KIT and tryptase. Molecular testing also identified the KIT D816V mutation, confirming an SM diagnosis.
Learn more about SM testing and diagnosis
Because the woman had anemia, gastrointestinal malabsorption and significant weight loss, her disease met the criteria for advanced SM. After diagnosis, she received the targeted therapy midostaurin alongside blood transfusions. At follow-up, the patient continued to require monthly transfusions and had only a partial response to treatment, with persistently elevated tryptase levels and ongoing diarrhea.
The authors note that the absence of skin involvement is more often associated with advanced forms of SM and can delay diagnosis. They suggest that the disease should be considered in people with persistent, unexplained gastrointestinal symptoms, particularly when accompanied by anemia or signs of malabsorption.
“This report aims to alert to the importance of considering gastrointestinal tract manifestations as part of the spectrum of rare systemic hematologic disorders, suggesting a careful approach for these patients,” the authors concluded.
Read more about SM and the GI system: “How does systemic mastocytosis affect the digestive system?”
