Haematology: paroxysmal nocturnal haemoglobinuria: practice question

A Pathology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Pathology · Haematology: paroxysmal nocturnal haemoglobinuria

Sample item

A 30-year-old woman has episodes of dark urine on waking, mild pancytopenia and a recent hepatic vein thrombosis. The direct Coombs test is negative. Which test is the best confirmation of the diagnosis?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Flow cytometry showing loss of CD55 and CD59 on blood cells

Paroxysmal nocturnal haemoglobinuria results from acquired PIGA mutation in a haematopoietic stem cell, causing loss of GPI-anchored proteins including CD55 and CD59, which normally inhibit complement. Red cells undergo complement-mediated intravascular haemolysis, and thrombosis at unusual sites is a main cause of death. Flow cytometry for CD55 and CD59 is the diagnostic test of choice, and eculizumab, a C5 inhibitor, is used for treatment.

Option by option

  • A. Bone marrow cytogenetics for t(9;22)

    The t(9;22) translocation indicates chronic myeloid leukaemia, which does not cause this picture.

  • B. Osmotic fragility test

    Osmotic fragility is raised in hereditary spherocytosis, and does not identify this disorder.

  • C. Flow cytometry showing loss of CD55 and CD59 on blood cells (correct)

    Correct. Loss of GPI-anchored complement regulators on the cells confirms the diagnosis.

  • D. Haemoglobin electrophoresis

    Haemoglobin electrophoresis identifies haemoglobinopathies and not complement-sensitive red cells.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More Pathology questions

Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is C, Flow cytometry showing loss of CD55 and CD59 on blood cells. Paroxysmal nocturnal haemoglobinuria results from acquired PIGA mutation in a haematopoietic stem cell, causing loss of GPI-anchored proteins including CD55 and CD59, which normally inhibit complement.

Why is "Bone marrow cytogenetics for t(9;22)" not the answer?

The t(9;22) translocation indicates chronic myeloid leukaemia, which does not cause this picture.

Why is "Osmotic fragility test" not the answer?

Osmotic fragility is raised in hereditary spherocytosis, and does not identify this disorder.

Why is "Haemoglobin electrophoresis" not the answer?

Haemoglobin electrophoresis identifies haemoglobinopathies and not complement-sensitive red cells.

What concept does this question test?

It tests Haematology: paroxysmal nocturnal haemoglobinuria in Pathology. Red cells undergo complement-mediated intravascular haemolysis, and thrombosis at unusual sites is a main cause of death. Flow cytometry for CD55 and CD59 is the diagnostic test of choice, and eculizumab, a C5 inhibitor, is used for treatment.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Haematology: paroxysmal nocturnal haemoglobinuria?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.