Histopathological and molecular findings in a patient with Ras-associated autoimmune leukoproliferative disorder

Ras-associated autoimmune leukoproliferative disorder (RALD) is a nonmalignant lymphoproliferative disease associated with somatic RAS mutations. It is characterized by autoimmune disease, lymphadenopathy, splenomegaly and monocytosis. Less than 30 cases of RALD have been reported in the literature. We report a 20-year-old female patient who presented with lymphadenopathy, splenomegaly and autoimmune cytopenia, without increased double-negative T-cells. We describe the histopathological features seen in this patient's lymph node and bone marrow. The lymph node showed paracortical expansion by histiocytes and T-cells, with reactive follicular hyperplasia and progressive transformation of germinal centers. The bone marrow demonstrated hypercellular marrow with increased histocytes, T-cells, plasma cells, and mild diffuse fibrosis. The 220-gene Next Generation Sequencing (NGS) identified a somatic KRAS gene mutation (KRAS p.A146P) with a 34% of variant allele frequency (VAF), which is not codon 12 or 13 of the KRAS gene frequently described in RALD patients. A diagnosis of RALD was proposed. The diagnosis of RALD requires the integration of multifaceted methods including clinical information, laboratory tests, histology, and molecular tests. The histological and molecular conformation we provide in this case report is a valuable addition to understanding the spectrum of RALD presentation.