A case study recently published in JACC: Case Reports describes a young girl with severe systemic mastocytosis (SM) who was initially misdiagnosed with malignant vasovagal syncope, a severe type of fainting.
The authors aimed to highlight a rare but critical diagnostic pitfall, showing that SM can mimic malignant vasovagal syncope, a neuronal mediated disorder that causes patients to faint in response to stimuli such as fear or sudden positional changes.
The histamine and tryptase released from mast cells in SM can cause profound blood vessel dilation (called vasodilation) and clot forming abnormalities. This combination can decrease the flow of blood to the brain and lead to fainting (syncope).
However, standard testing to determine the reason for fainting may miss underlying clonal mast cell disease.
Read more about SM testing and diagnosis
In this case, a 12-year-old girl had experienced recurrent fainting episodes over several years. The episodes were characterized by symptoms such as vomiting, diarrhea, sweating and pallor that preceded a brief loss of consciousness, with no clear triggers or consistent pattern.
She was initially diagnosed as having reflex vasovagal syncope. Despite typical treatments for syncope, her condition persisted. At 13 she experienced a severe episode that impacted the flow of blood to the brain and led to vision problems and speech loss.
Further testing revealed abnormal coagulation results and transiently elevated tryptase levels. These findings, along with a bone marrow biopsy, ultimately confirmed the diagnosis of severe SM. The girl was treated with antihistamines and other medications to manage mast cell mediator release.
SM should be considered when recurrent fainting episodes are unexplained, especially in cases with abnormal coagulation findings and elevated tryptase levels.
“Systemic mastocytosis should be systematically considered in case of any unexplained hypovolemic shock or recurrent syncope with vasovagal features,” the authors wrote.
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