Two cases involving patients with systemic mastocytosis (SM) without KIT mutations (KIT negative) have been recently reported in the Journal of Hematology.
SM is a hematological disease characterized by excessive mast cell activation and infiltration of tissues such as the gastrointestinal tract. Clinical manifestations are diverse, as the disease can affect several organ systems. However, an important percentage of patients do not exhibit symptoms.
The disease is caused by genetic mutations; the KIT gene appears to be the most effected. According to the World Health Organization (WHO), detecting a KIT mutation is one of the minor criteria required for SM diagnosis, but its absence does not exclude SM.
Learn more about SM causes and risk factors
“Although identifying KIT-activating gene mutation, specifically at codon 816, is considered a fundamental part of the diagnosis and is one of the four minor criteria according to the ICC diagnostic criteria for SM, its negativity does not exclude the diagnosis,” the authors stated.
The first case involved a 49-year-old woman with a history of recurrent itchy rashes in the past four years. The patient sought medical assistance due to dizziness, nausea, and vomiting; laboratory examination upon admission revealed a low platelet count and high tryptase levels, a minor criterion for SM diagnosis.
A subsequent bone marrow exam revealed mast cell infiltration and the presence of cellular markers associated with SM, such as CD117 and CD68. Despite all of the findings pointing towards SM, KIT testing turned out negative. The physicians started treatment for SM, and the patient is currently doing well.
The second case involved a 40-year-old man with a 10-year history of recurrent skin rashes, gastrointestinal symptoms, difficulty breathing, and loss of consciousness. Initial blood tests showed increased eosinophils, which prompted the physicians to perform a bone marrow biopsy that showed findings compatible with SM. As in the previous case, the patient had no KIT mutations. After the initiation of treatment, symptoms improved.
“Further and more comprehensive research is needed to expand our understanding of KIT-D816V-negative SM and determine the most appropriate management and prognosis,” the authors wrote.
