Pancytopenia Revealing Phenylketonuria: Coincidence or First Case Report

Pancytopenia in childhood can be caused by a variety of underlying diseases including hematological and non-hematological entities. Phenylketonuria (PKU) is an inborn error of phenylalanine metabolism. No association between PKU and pancytopenia has ever been reported. We report the first case of PKU revealed by a pancytopenia at presentation. The patient was an infant girl born to healthy non-consanguineous parents with unremarkable family history. A hereditary metabolic disease workup was performed due to the presence of unexplained hematological features and a global developmental delay. Plasma aminoacid profile by thin-layer chromatography showed elevation of phenylalanine and urine organic acid chromatography showed accumulation of metabolites of phenylalanine; whereas, methylmalonic acid or other abnormal organic acids were not found. This is the first case of untreated PKU associated with pancytopenia who improved with low-phenylalanine diet.