Bombay blood group is a rare group with?

SCTIMST Staff Nurse - 2016

Pathology & Genetics

Medium

Appeared in: SCTIMST Staff Nurse - 2016

Explanation

The Bombay blood group (Oh phenotype) is defined by the absence of the H antigen on the surface of red blood cells (RBCs).
This absence is due to a homozygous recessive genotype (hh), which prevents the formation of the H substance.
Because the H antigen is the precursor for A and B antigens, these are also absent.
The immune system of an individual with Bombay blood recognizes the H antigen as foreign and produces potent anti-H antibodies in the serum.
Therefore, the defining characteristics are the lack of H antigen on RBCs and the presence of anti-H antibodies in the serum.

Option A: This is incorrect. The Bombay blood group is characterized by the complete absence of A, B, and H antigens on red blood cells.
Option C: While it is true that individuals with Bombay blood group lack A, B, and H antigens, this statement is incomplete. It omits the clinically crucial presence of anti-H antibodies in the serum, which is a key part of its definition and what distinguishes it from the O group in cross-matching.
Option D: This is the opposite of the Bombay phenotype. Individuals with this blood group lack the H antigen and possess anti-H antibodies.

Clinical Relevance

Nursing practice connection: Knowing Characteristics of the Bombay blood group (Oh phenotype) helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
The primary clinical relevance is in blood transfusion. A patient with Bombay blood group can only receive blood from another Bombay blood group individual.
Transfusing blood from a regular Group O donor (universal donor) is extremely dangerous for a Bombay patient. The donor's RBCs have H antigen, which will react with the recipient's potent anti-H antibodies, causing a severe hemolytic transfusion reaction.
What if? If a patient with a known Bombay phenotype presents with severe anemia requiring transfusion and no compatible blood is available in the blood bank, the nurse must immediately escalate to the treating physician and blood bank officer. The protocol involves contacting a national or regional rare donor registry to locate a suitable donor. In non-emergent cases, autologous (self-donated) transfusion may be planned before surgeries.

How to Approach the Question

First, identify the core of the question, which is to define the Bombay blood group.
Recall the fundamental principles of the ABO and Hh blood group systems. Remember that the H antigen is the precursor substance upon which A and B antigens are built.
The defining feature of the Bombay phenotype is a genetic defect (hh genotype) that prevents the formation of the H antigen.
Deduce the consequences of this defect: 1) No H antigen on red cells. 2) No A or B antigens can be formed. 3) The immune system produces anti-H antibodies because it sees H antigen as foreign.
Evaluate the given options against these facts. The most complete and accurate description is that the group has 'Anti-H and no H antigen', as this captures both the antigen deficiency and the resulting immunological response that makes it unique.

Concept Tested & Keywords

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E6 Physiology Essentials Sembulingam 10e Part 1 p. 151-153

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