PNH (paroxysmal nocturnal haemoglobinuria)

Exam Cram

• In PNH (paroxysmal nocturnal haemoglobinaemia) the immune system destroys RBCs because they are faulty

• Presentation: 2 weeks- dark urine in mornings, short of breath & reduced exercise tolerance

• Investigations: haemolytic anaemia- low Hb, low haptoglobin, haematuria

• Diagnosis: Flow cytometry- reduced CD59 & CD55 expression

Outline

Background

• Acquired haematopoetic stem cell disorder

Assessment

History

• < 30yrs

• Passing brown/ dark / bloody urine at night

• Recent URTI

Examination

• Purpura on limbs

• Borderline febrile

• Venous thrombosis

Investigations

• Haemolytic anaemia

  • Low Hb, normal MCV, raised haptoglobin

  • Blood film: schistocytes

  • Urine analysis: blood without red cells

• Flow cytometry: expression of CD 55 & CD 59

Diagnosis & Classification

Diagnostic Criteria: flow cytometry expression of CD 55 & CD 59

Differentials: 

• IgA Nephropathy & Poststreptococcal Glomerulonephritis - neither have anaemia

• Hereditary Spherocytosis : splenomegaly, chronic haemolysis

Classification:

Management

Acute

• Haematology consult

• Consider anticoagulation or eclizumab

Med Reg Notes

May also present with aplastic anaemia

Increased risk of VTE (DVT, Pulmonary Embolus )

References and Resources

1. https://rarediseases.org/rare-diseases/paroxysmal-nocturnal-hemoglobinuria/

Written in 2025