Rh-null, Amorph Type; Rhna

Description

The RH-null phenotype designates rare individuals whose red blood cells lack all Rh antigens. Two RH-null types, the regulator type (OMIM ) and the amorph type, arising from independent genetic mechanisms have been distinguished. The regulator type is caused by mutation in the RHAG gene (OMIM ). The amorph type arises from mutations at the RH locus itself that silence Rh expression. The RH locus contains the RHD (OMIM ) and RHCE genes tandemly arranged at chromosome 1p36-p34. Four genes must therefore be silenced to produce the RH-null phenotype. The absence of the D antigen, produced by the RHD gene, is common in the human population; the D-negative phenotype may result from deletion or genetic alteration of the RHD gene. The RH-null amorph phenotype thus arises from inactivating mutations in RHCE on a D-negative background (summary by Huang et al., 1998, Huang et al., 2000).Clinically, Rh-null patients present mild to moderate hemolytic anemia; cells exhibit characteristic morphologic and functional abnormalities including spherocytosis, stomatocytosis, and diminished lifespan. Rh-null patients rarely develop antibodies without stimulation, and most cases occur in response to pregnancy or transfusion (Silvy et al., 2015).

Clinical Features

• Anemia
• Jaundice
• Hemolytic anemia
• Spherocytosis
• Stomatocytosis