Paroxysmal Nocturnal Hemoglobinuria (PNH) – YES, it shows up on Step 1, and you need to know the essentials!

Here’s what you need to remember:

- PIGA gene mutation in hematopoietic stem cells

- Deficiency of CD55 and CD59

- Complement-mediated intravascular hemolysis

- Classic triad: hemolytic anemia, pancytopenia, and venous thrombosis (think Budd-Chiari syndrome)

✅ Diagnosis: Flow cytometry

✅ Treatment: Eculizumab

💡 Exam clue: patient waking up with dark urine in the morning = think PNH!