Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 12 3 2018 07 04 180 183 EN Ehsan Shahverdi Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran Mostafa Moghaddam Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran Hassan Abolghasemi Pediatric Congenital Hematologic Disorders Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2017 11 05 2018 02 26 Rhnull phenotype is a rare blood group with a frequency of approximately 1 in 6 million individuals, transmitted via an autosomal recessive mode. It is characterized by the weak (Rh mod) or lack (Rh null) of expression of all Rh antigens on the red cells. The clinical significance of its assessment is that such patients with Rhnull syndrome are associated with chronic hemolytic anemia of varying degrees. Another clinical importance is that such subjects readily form alloantibodies when exposed to Rh antigens. We report herein a rare Rhnull phenotype in a sibling which was detected as a part of the difficult sample work-up for red cell antibody screening and identification.   https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/877 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/877/638