Polycythemia from mast cell activation syndrome: lessons learned.

Area of Science:

• Hematology
• Immunology
• Oncology

Background:

• Polycythemia vera is a myeloproliferative neoplasm characterized by increased red blood cell mass.
• Diagnostic challenges arise when initial presentations are atypical or do not respond to standard treatments.

Observation:

• A middle-aged woman with fatigue and elevated hematocrit was initially diagnosed with polycythemia vera.
• Despite therapeutic phlebotomy, her condition worsened, revealing additional symptoms like rash and vasomotor issues.
• Standard JAK2V617F mutation testing was negative, prompting further investigation into paraneoplastic erythrocytosis and mast cell disorders.

Findings:

• Elevated urinary prostaglandin D2 levels were noted, with biopsies revealing increased aberrant mast cells in the gastrointestinal tract.
• The patient was diagnosed with mast cell activation syndrome, a clonal disorder involving KIT mutations.
• Treatment with imatinib 200 mg/d led to a rapid, complete, and sustained clinical response.

Implications:

• Mast cell activation syndrome can mimic other hematologic conditions, necessitating comprehensive diagnostic approaches.
• Early and accurate diagnosis of mast cell activation syndrome is crucial for effective management and improved patient outcomes.
• Targeted therapies like imatinib demonstrate significant benefit in managing mast cell activation syndrome, even in complex cases.