Abstract
Proprotein convertase 1/3 (PC 1/3) deficiency is a rare, autosomal recessive disorder caused by mutations in the PCSK1 gene. The disease is characterized by early-onset chronic diarrhea/malabsorption, followed by severe obesity and hormonal deficiencies such as hypocortisolism, hypothyroidism, diabetes insipidus, hypogonadism, growth deficiency, and diabetes mellitus. Ewing's sarcoma is a rare tumor, usually of small dimensions of neuroectodermal origin that is difficult to distinguish pathologically from a primitive neuroectodermal tumor. A 22-year-old female patient with PC 1/3 deficiency was admitted to our clinic with recurrent urinary tract infections. Magnetic resonance imaging (MRI) revealed an 11x12 cm pelvic mass displacing the uterus. A core-needle biopsy was performed on the pelvic mass. As a result of the pathological evaluation, ıt was diagnosed with pelvic Ewing's sarcoma. The patient was started on the VAC-IE chemotherapy protocol. We report a case of pelvic Ewing's sarcoma in a patient with PC 1/3 deficiency. Further research is needed to assess malignancy risk in metabolic disorders including very rare disorders like PC 1/3 deficiency.