Systemic Mastocytosis (SM)

Mastocytosis comprises a group of diseases in which pathologic mast cells proliferate and accumulate in the tissues in excessive amounts. Systemic mastocytosis (SM), specifically, is a severe form of mastocytosis marked by the release of many vasoactive cell mediators as a result of excessive mast cell activity, which can cause a wide range of symptoms.1 

SM can lead to a variety of complications. It can induce blood diseases such as anemia or disruptions in blood clotting in the event of injury. The reduction in bone density in osteoporosis can be accelerated by the accumulation of mast cells in bone tissues. Anaphylactic reactions that lead to shock, fainting, elevated pulse rate, and loss of consciousness are another complication. Failure of organ function can also occur as a consequence of marked allergic reactions. Bleeding in the gastrointestinal tract can be caused by peptic ulcer disease.2,3 

Hematological Complications

Hematological abnormalities and complications may occur in patients with all subtypes of SM. The most prevalent issue is anemia, which affects 30% to 50% of affected individuals.Thrombocytopenia and leukopenia are seen in 20% to 30% of cases, and leukocytosis in approximately 25%. Monocytosis develops in approximately 15% of patients; lymphocytosis and thrombocytosis are uncommon. Eosinophilia can be seen in as many as 40% of patients with SM. Circulating eosinophils in SM are usually hypogranular with hypersegmented nuclei (3-5 lobes per nucleus) and resemble the eosinophils found in idiopathic hypereosinophilic syndrome.4,5 Several malignant or premalignant hematological disorders have been found in patients with SM. Myeloproliferative disorder, myelodysplastic syndrome, “lymphadenopathic syndrome,” lymphoreticular malignancy, and (secondary) acute leukemia are some examples. Some patients with SM experience clinically substantial bleeding. Mast cells produce heparin when they are stimulated. As a result, significant amounts of heparin can be found in sites with dense populations of mast cells.4 

Anaphylactic Reaction 

The prevalence of anaphylaxis in adult patients with various forms of mastocytosis has been reported to be 20% to 56%.6 Flushing, syncope, gastrointestinal complaints, and vascular collapse are common signs of anaphylaxis. Urticaria and angioedema are observed less commonly. These reactions can be caused by immunoglobulin E-mediated allergies or by nonspecific mast cell activation.1

Gastrointestinal Complications 

Mastocytosis is associated with gastrointestinal complications in up to 80% of patients. An increased risk for duodenal ulcers has been noted. SM can be a rare cause of recurrent gastrointestinal bleeding; this is hypothesized to result from the hypersecretion of gastric acid in response to increased serum levels of histamine, which may lead to peptic ulcer disease. In patients who have SM with gastrointestinal symptoms, ulcer bleeding, ulcer perforation, and severe esophagitis have been documented. Treatment includes addressing the underlying disease, acid suppression, and if necessary endoscopic or surgical treatment.7 

Bone Complications 

A subpopulation of patients with SM tend to have a higher risk for osteopenia and osteoporosis. Bone densitometry is indicated to check for osteoporosis in all patients with SM.1 Poorly localized bone pain, widespread osteoporosis or osteopenia, pathological fractures, and skeletal abnormalities are all possible presentations. Mast cell infiltration or mast cell mediators are thought to be the main factors contributing to bone loss and the pathophysiology of osteoporosis.8 In a recent study of patients with SM, it was discovered that 49% had bone involvement, the most common form of which was osteoporosis (31%).9

Cardiovascular Complications

An increased risk for cardiovascular complications in patients who have SM with an associated non-mast cell lineage clonal hematological disease (SM-AHNMD) has been noted in some studies. In addition, a greater risk for thromboembolic episodes has been noted in patients who have the JAK2 V617F mutation than in those who do not have this mutation.10 

Pulmonary Complications 

Pulmonary involvement and complications may occur in fewer than 20% of cases of SM. Cough, dyspnea, and asthma-like symptoms are the pulmonary manifestations observed. Chest radiography shows interstitial fibrosis and pulmonary nodules. Computed tomography shows nodular and reticular opacities in addition to enlarged mediastinal lymph nodes.11 


  1. Gangireddy M, Ciofoaia GA. Systemic mastocytosis. StatPearls [Internet]. Published July 21, 2021. Accessed April 17, 2022.
  2. Systemic mastocytosis. Mayo Clinic. Accessed April 17, 2022. 
  3. Systemic mastocytosis – symptoms, causes, complications and treatment. AskApollo. Updated February 3, 2022. Accessed April 17, 2022. 
  4. Parker RI. Hematologic aspects of systemic mastocytosis. Hematol Oncol Clin North Am. 2000;14(3):557-568. doi:10.1016/s0889-8588(05)70296-3
  5. Robyn J, Metcalfe DD. Systemic mastocytosis. Adv Immunol. 2006;89:169-243. doi:10.1016/S0065-2776(05)89005-4
  6. Gülen T, Hägglund H, Dahlén B, Nilsson G. High prevalence of anaphylaxis in patients with systemic mastocytosis – a single-centre experience. Clin Exp Allergy. 2014;44(1):121-129. doi:10.1111/cea.12225
  7. Faruqui S, Rhodes B, Hutchings JJ, et al. Systemic mastocytosis: a rare cause of gastrointestinal hemorrhage, Am J Gastroenterol. 2017;12:S1357-S1358.
  8. Guillaume N, Desoutter J, Chandesris O, et al. Bone complications of mastocytosis: a link between clinical and biological characteristics. Am J Med. 2013;126(1):75.e1-75.e757. doi:10.1016/j.amjmed.2012.07.018
  9. Barete S, Assous N, de Gennes C, et al. Systemic mastocytosis and bone involvement in a cohort of 75 patients. Ann Rheum Dis. 2010;69(10):1838-1841. doi:10.1136/ard.2009.124511
  10. Suppa M, Marino L, Piccari P, Masselli G, Gradini R. Cardiac complications in a patient affected by systemic mastocytosis and primitive myelofibrosis: a case report. Clin Case Rep. 2021;9(11):e04972. doi:10.1002/ccr3.4972
  11. Pillai R, Maehara D, Chitkara N. Systemic mastocytosis with pulmonary involvement. Chest. 2016;150(4 Suppl):1136A.

Reviewed by Kyle Habet, MD, on 4/21/2022.