You're probably aware that some blood types are less common than others. Roughly 40% of Americans are O positive, for instance, while less than 1% of the population share an AB negative blood type.
In that context, AB negative is absolutely a rare blood type. But is it the rarest? No — not by a longshot.
That title goes to Rhnull, a blood group so extraordinarily rare that it has only been found in 48 humans... ever.
Rhnull, the 'Golden Blood Type'
First discovered in 1961 in an Indigenous Australian woman, Rhnull soon earned the nickname "golden blood" not because of its color but because of its immense value in transfusion medicine. While those with O negative blood are considered universal donors for the vast majority of patients, Rhnull blood is thought to be "universal" for anyone with rare blood types within the Rh system.
Why? Because Rhnull, unlike every other known blood type, lacks all Rh antigens — a fact that led doctors to initially suspect that no one with the blood type could live into adulthood.
Now, with dozens of documented cases of Rhnull blood in adults, that belief has been disproven, though we now know that having Rhnull blood often comes with a unique and often significant set of health challenges.
Health Concerns for Rhnull Patients
Since this blood type is so rare, finding compatible blood for transfusions is exceptionally difficult. The number of Rhnull donors is reportedly less than 10 worldwide.
Since Rhnull donors are so few, their donations are often frozen for long-term storage. However, logistical challenges, such as maintaining appropriate storage conditions and ensuring the timely delivery of blood to patients in critical need, make the management of Rhnull blood especially complex. To complicate matters further, the structural abnormalities of Rhnull red blood cells can lead to hemolytic anemia and, consqeuently, a low RBC count.
These obstacles makes it crucial for Rhnull individuals to store their own blood for emergencies. They're even discouraged from engaging in potentially injurious behaviors like riding a motorcycle or participating in military service as they must take extra precautions to avoid accidents that might necessitate a transfusion.