From the Guidelines
The elevated histamine level of 1.51 ng/ml, presence of nucleated red blood cells (nRBCs) at 0.3, and low mean platelet volume (MPV) suggest a potential hematologic disorder, most likely mast cell activation syndrome (MCAS) or systemic mastocytosis, which warrants prompt hematology consultation and further evaluation. The elevated histamine level is particularly concerning as it indicates mast cell activation or proliferation, which can cause symptoms like flushing, itching, gastrointestinal disturbances, and hypotension 1. The presence of nRBCs in peripheral blood indicates stress erythropoiesis or bone marrow infiltration, while low MPV suggests altered platelet production.
According to the most recent guidelines, patients with MCAS can have a variable clinical phenotype affecting multiple organ systems, and a key feature is recurrent episodes of systemic anaphylaxis with concurrent involvement of at least 2 of the 4 organ systems listed 1. The clinical symptoms have to be associated with an acute increase in specific biologic mediator levels, and patients should respond to therapy with MC mediator blocking agents, MC stabilizers, or both.
While awaiting specialist evaluation, the patient should avoid known histamine triggers and may benefit from H1 antihistamines (such as cetirizine 10mg daily) and H2 blockers (such as famotidine 20mg twice daily) to manage symptoms. The findings together point to bone marrow dysfunction that requires thorough investigation to determine appropriate treatment, which may range from observation to targeted therapies depending on the specific diagnosis. It is essential to measure mediator levels at baseline and during an acute episode to confirm the diagnosis of MCAS 1.
Some key points to consider in the evaluation and management of this patient include:
- Measuring mediator levels, such as histamine, PGD2, and LTC4, and their metabolites, to confirm the diagnosis of MCAS 1
- Implementing therapies directed at the increased mediator, such as histamine-blocking agents or aspirin, to alleviate symptoms 1
- Avoiding known histamine triggers and managing symptoms with H1 antihistamines and H2 blockers while awaiting specialist evaluation
- Considering a bone marrow biopsy for definitive diagnosis of systemic mastocytosis or other myeloproliferative neoplasms 1
From the Research
Histamine Plasma Levels and Correlations
- The patient's histamine plasma level is 1.51 ng/ml, which is elevated according to some studies 2, 3.
- Elevated histamine levels have been associated with histamine intolerance, mast cell disorders, and other conditions 2, 3.
- A study found that 24% of patients with suspected histamine intolerance had elevated histamine levels during the day, which may be caused by reduced diamine oxidase (DAO) activities 2.
Nucleated Red Blood Cell (NRBC) Count
- The patient's NRBC count is 0.3, which may indicate some level of stress or inflammation in the body 4.
- NRBC counts are not typically elevated in healthy individuals and may be associated with various conditions, including anemia, sepsis, and other diseases 4.
Mean Platelet Volume (MPV) and Correlations
- Low MPV values may be associated with various conditions, including thrombocytopenia, anemia, and other diseases 4.
- There is limited information available on the correlation between histamine plasma levels, NRBC counts, and low MPV values.
- Further studies are needed to fully understand the relationships between these parameters and their clinical implications 4.