Myeloid/Lymphoid Neoplasm with FGFR1 Rearrangement Presenting with Polycythemia Vera and T-cell Acute Lymphoblastic Leukemia.

Myeloid/lymphoid neoplasm with fibroblast growth factor 1 rearrangements (MLN-FGFR1) represents a rare group of hematologic neoplasms, with approximately 100 cases reported to date. A 69-year-old woman with a history of polycythemia and leukocytosis, with negative molecular testing for JAK2, CALR, and MPL, presented with diffuse adenopathy. A lymph node (LN) biopsy revealed effacement by T-lymphoblasts, consistent with T-cell acute lymphoblastic lymphoma (T-ALL). A staging bone marrow (BM) biopsy demonstrated trilineage hyperplasia, which, taken together with the patient's elevated hemoglobin and low serum erythropoietin level, fulfilled diagnostic criteria for polycythemia vera. Karyotype and fluorescence in situ hybridization on both the BM and LN demonstrated a FGFR1 rearrangement due to t(8;13), consistent with MLN-FGFR1. Whole genome sequencing on the LN additionally identified a pathogenic frameshift mutation of ASXL1 NC_000020.11:g32434646dup NM_015338.6(ASXL1):c.1934dup p.(Gly646Trpfs) predicted to result in loss of protein function, a finding also observed in 8.1% of BM reads. Both the BM and LN harbored missense variants in HDAC4 NM_001378414.1(HDAC4):c.[2763G>A]; [2763=] p.(Met921Ile) and CHEK2 NM_007194.4(CHEK2):c.[538C>T];[538=] p.(Arg180Cys), with an unknown significance. Despite initial response to Mini-CVD + venetoclax, the patient subsequently experienced rapid clinical deterioration and death. We report the second case of MLN-FGFR1 with an ASXL1 mutation and the first case with HDAC4 and CHEK2 variants.

Pulmonary Microscopic Polyangiitis Presenting as Acute Respiratory Failure from Diffuse Alveolar Hemorrhage.

Microscopic polyangiitis and granulomatosis with polyangiitis are rare anti-neutrophilic cytoplasmic antibody-associated systemic vasculitides that predominantly affect small to medium sized vessels of the lungs and kidneys. These syndromes are largely confined to older adults and often present sub-acutely following weeks to months of nonspecific prodromal symptoms. While both diseases often manifest within multiple organ systems concurrently, the disease spectrum of microscopic polyangiitis almost always includes the kidneys, while granulomatosis with polyangiitis is most commonly associated with pulmonary disease. We present two cases of rapid onset respiratory failure secondary to diffuse alveolar hemorrhage in young active duty military personnel. After serological testing and surgical lung biopsy, both patients were diagnosed with microscopic polyangiitis with isolated pulmonary involvement.