SP20 | SYSTEMIC MASTOCYTOSIS AND CONCOMITANT FOLLICULAR LYMPHOMA IN A 67-YEAR-OLD FEMALE

Systemic mastocytosis (SM) is a rare hematologic disorder characterized by the abnormal accumulation of mast cells in various organs. SM associated with hematologic neoplasms (SM-AHN) accounts for approximately 5% of SM cases, most commonly of myeloid origin. This case reports the management of a 67-year-old woman diagnosed with advanced-stage follicular non-Hodgkin lymphoma (FL) and concomitant systemic mastocytosis. Case report The patient presented with left periorbital swelling, with imaging and biopsy leading to the diagnosis of FL. Her medical history included a prior diagnosis of mastocytosis, plaque psoriasis, and psychiatric disorders. Laboratory results showed neutrophilic leukocytosis, hypogammaglobulinemia, and an elevated serum tryptase level (65.4 µg/L). Bone marrow biopsy revealed lymphoid infiltration with multifocal clusters of mast cells, some with atypical morphology, the KIT D816V mutation was absent. The diagnosis of SM-AHN (WHO 5th ed.) was consequently established. The treatment for FL included six cycles of bendamustine and rituximab, followed by maintenance therapy with rituximab. However, the patient experienced a severe anaphylactic reaction to rituximab, despite premedication. The treatment plan was adjusted to exclude rituximab, and the patient continued with bendamustine monotherapy for five additional cycles. Local radiotherapy was planned for the orbital mass. The response will be assessed by a bone marrow biopsy, and a lymph node biopsy will be considered if PET imaging shows significant uptake. Conclusion This case emphasizes the complexity of managing SM-AHN, particularly with lymphoid malignancies. The risk of hypersensitivity reactions requires careful infusion protocols. The absence of the KIT D816V mutation highlights the need for broader KIT mutation screening in SM management. Long-term follow-up for SM includes biannual serum tryptase measurement, bone densitometry, and vigilant disease monitoring. In SM-AHN, follow-up should integrate protocols for both conditions, with more frequent evaluations during active treatment. Multidisciplinary collaboration is essential for managing dual pathology, and PET imaging should be interpreted with caution. This case underscores the need for individualized treatment and close surveillance of both conditions, considering their interactions.