Systemic Mastocytosis Associated with "Smoldering" Multiple Myeloma

Area of Science:

• Hematology
• Oncology
• Genetics

Background:

• Systemic mastocytosis (SM) and multiple myeloma (MM) are distinct hematologic malignancies.
• The co-occurrence of SM and MM is exceptionally rare, presenting unique diagnostic and therapeutic challenges.
• Patients with SM may exhibit associated clonal hematologic non-mast cell lineage diseases (SM-AHN).

Purpose of the Study:

• To report a rare case of coexisting systemic mastocytosis and multiple myeloma.
• To describe the clinical presentation, diagnostic findings, and molecular characteristics of this dual malignancy.
• To discuss the classification and management of SM-AHN.

Main Methods:

• Clinical case presentation and review of patient history.
• Laboratory investigations including peripheral blood counts, serum tryptase, and immunofixation.
• Bone marrow biopsy with histopathological examination and molecular analysis (mutation profiling).
• Skeletal imaging (X-rays, MRI) and bone density study.

Main Results:

• The patient presented with peripheral eosinophilia, anemia, and elevated beta-2 microglobulin and tryptase.
• Bone marrow biopsy revealed concurrent mast cell proliferation (20%) and plasma cell aggregates (40%).
• Molecular analysis identified KIT D816V, TET2 mutations, TP53 deletion, and ATM trisomy.
• Diagnosis confirmed as SM with associated clonal hematologic non-mast cell lineage disease (SM-AHN) and multiple myeloma.

Conclusions:

• The coexistence of systemic mastocytosis and multiple myeloma represents a rare subtype of SM-AHN.
• Accurate diagnosis requires comprehensive evaluation including bone marrow morphology and molecular genetics.
• Management strategies must address both neoplastic processes, with targeted therapies like midostaurin initiated.