Rh-null blood type is extremely rare.  It is known as the golden blood owing to its rarity.

Individuals with a Rh null blood type should be transfused with blood products of same blood type in order to avoid hemolytic transfusion reactions.

Rh null individuals, if exposed to normal Rh cells through transfusion or pregnancy, can produce a potent antibody which reacts strongly with all red cells except Rh null cells.

Individuals who lack all Rh antigens on their RBCs are said to have Rh null syndrome, which can be produced by two different genetic mechanisms.

1. THE REGULATOR TYPE– Rh null

Mutation occurs in the RHAG gene

This results in no RhAG protein expression and subsequently no RhD or RhCE protein expression on the RBCs

These individuals can pass normal RHD and RHCE genes to their children

2. THE AMORPHIC TYPE- Rh null

There is a mutation in each of the RHCE genes

There is a mutation in each of the RHCE genes inherited from each parent as well as the deletion of the RHD gene found in most D-negative individuals.

The RHAG gene is normal.

Rh mod: A related and often confusing term is Rh mod: Rhmod phenotype refers to severely reduced expression of all Rh antigens.

THE RH NULL SYNDROME

Symptoms of Rh null syndrome include

1. Mild compensated hemolytic anemia

2. Reticulocytosis

3. Stomatocytosis

4. A slight-to-moderate decrease in hemoglobin and hematocrit levels

5. An increase in hemoglobin F

6. Decrease in serum haptoglobin

7. Elevated bilirubin level.

Reference: Modern blood banking by Harmening 7th edition.