Duffy Null Polymorphism

**Semantic type:** Laboratory or Test Result

**Definition:** A finding indicating that expression of atypical chemokine receptor 1 protein (ACKR1; DARC; Duffy antigen/chemokine receptor) is not detected on a subject's red blood cells. The Duffy null state is associated with leukopenia and neutropenia, decreased rate of HIV disease progression and with resistance to infection by the malarial parasite Plasmodium vivax. (Blood. 2009; 114:2783-2792.)

**Synonyms:** - ACKR1 Negative - DARC Negative - Duffy Negative - Duffy Null - Duffy-Null State - Fy(a-b-) - Fy(a-b-) Phenotype