" />
Blood group, john milton hagen system - CISMeF
Blood group, john milton hagen systemOMIM Phenotype
Preferred Label : Blood group, john milton hagen system;
Symbol : JMH;
CISMeF acronym : JMH;
Type : Phenotype, molecular basis known;
Alternative titles and symbols : John milton hagen blood group system; Jmh blood group system;
Description : JMH blood group antigens are carried by SEMA7A, a membrane-associated protein that
plays important roles in the nervous system and immune responses. Three different
JMH phenotypes have been identified based on the presence or absence of the high-frequency
JMH (or JMH1) antigen: JMH-weak, JMH-negative, and JMH-variant. The JMH-weak and -negative
phenotypes can be either acquired or inherited and are characterized by a reduction
or complete loss of JMH expression on red blood cells (RBCs), often with concomitant
occurrence of JMH antibodies. Acquired JMH-weak or -negative phenotypes are typically
found in elderly persons and can be transient. The JMH antibodies present in the acquired
phenotypes have autoimmune characteristics and are clinically irrelevant. The inherited
JMH-negative phenotype has been found in only 1 family. Mechanisms underlying the
JMH-weak and -negative phenotypes have yet to be identified. Individuals with the
JMH-variant phenotype are usually JMH-positive and have alloantibodies compatible
with JMH-negative RBCs. The JMH-variant phenotype results from rare missense mutations
in the SEMA7A gene (summary by Seltsam et al. (2007) and Richard et al. (2011)).;
CISMeF manual mappings