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Paroxysmal Nocturnal Hemoglobinuria

Also called PNH, Marchiafava-Micheli Syndrome

Paroxysmal Nocturnal Hemoglobinuria results from acquired somatic mutations in the PIGA gene, which encodes a protein essential for biosynthesis of glycosylphosphatidylinositol (GPI) anchors. These anchors normally attach proteins that protect blood cells from complement-mediated destruction.

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About Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal Nocturnal Hemoglobinuria results from acquired somatic mutations in the PIGA gene, which encodes a protein essential for biosynthesis of glycosylphosphatidylinositol (GPI) anchors. These anchors normally attach proteins that protect blood cells from complement-mediated destruction. Loss of GPI anchors leaves red blood cells, white blood cells, and platelets vulnerable to complement-mediated lysis. Hemolysis can be intravascular (within blood vessels) or extravascular (in spleen), leading to hemolytic anemia. Dark urine (hemoglobinuria) occurs from hemoglobin excretion in urine. A major complication is thrombosis (blood clots) due to complement activation, endothelial damage, and platelet activation, with venous thrombosis being most common (portal vein, hepatic vein, deep veins, cerebral veins). Thrombotic events can be life-threatening. Smooth muscle dystonia (involuntary smooth muscle contraction) can cause severe abdominal pain, urinary symptoms, and erectile dysfunction. Chronic hemolysis causes iron loss and secondary effects. Patients may develop aplastic anemia or myelodysplastic syndrome as complications.

Common Symptoms

  • Hemoglobinuria (dark red or brown urine, especially after sleep)
  • Fatigue and weakness from hemolytic anemia
  • Shortness of breath and chest discomfort
  • Back pain, abdominal pain, or leg pain (from thrombosis)
  • Headaches and neurologic symptoms
  • Smooth muscle dystonia causing abdominal or urinary symptoms

Who It Affects

Paroxysmal Nocturnal Hemoglobinuria can develop at any age, from childhood to elderly, with median age of diagnosis around 35-40 years. It affects males and females equally. The disease occurs across all racial and ethnic groups. It is acquired somatically and not inherited, resulting from a single PIG-A gene mutation in a hematopoietic stem cell that then expands clonally. About 10-25% of PNH patients have concurrent myelodysplastic syndrome or aplastic anemia.

Getting Involved in Clinical Trials

Clinical trials for Paroxysmal Nocturnal Hemoglobinuria focus on complement inhibitors at various pathway points, with several now FDA-approved, and newer agents continuing to expand treatment options. Trials investigate combination approaches, optimal timing of treatment initiation, and strategies to achieve complete complement inhibition. Research explores recovery of GPI-anchored protein expression through gene therapy. Patients should consult with a PNH specialist and consider enrollment in disease registries to track long-term outcomes.

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