Paroxysmal Nocturnal Hemoglobinuria (PNH)


Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic condition characterized by marked episodes of intravascular hemolysis and venous thrombosis due to acquired somatic mutations of hematopoietic stem cells.1 Over the past few centuries, many individuals have contributed to the identification, description, and understanding of the pathogenesis of PNH.2

First Description of PNH in the Literature

Paul Strübing, a German physician working at the Medical Clinic of Professor Mosier of Greifswald, first accurately described PNH in 2 papers published in 18821-5; however, he did not give the condition a name. He described PNH as a disease entity distinct from 2 other syndromes known at the time: paroxysmal cold hemoglobinuria and march hemoglobinuria. These syndromes shared overlapping symptoms with PNH.2,3

Strübing began treating a 29-year-old cart maker in November 1880. The patient traced his illness back to his years in the military service, particularly following bouts of heavy physical exertion. Even after his military discharge in 1876, the patient noticed that his urine was a dark brown or black color first thing in the morning, but by midday, it had regained a normal yellow tint. He complained of extreme fatigue, especially on exertion, shortness of breath, heart palpitations, vertigo, and pain and tenderness upon palpation around the spleen with lesser pain around the liver and kidneys.2 

Strübing also observed pallor and jaundice in the patient’s complexion. He astutely noted that after severe attacks, the plasma of his patient’s blood was red, suggesting that red blood cells were dissolved within the blood vessels and not within the kidneys or urine. Researchers debated the mechanism of hemoglobinuria even up until 1911, so Strübing was ahead of his time.2,5

Strübing used spectroscopy to identify hemoglobin as the cause of urine discoloration, although he did not attribute the pigmentation to hemosiderin. He also observed that erythrocytes remained absent from the urine, except after severe attacks.5 

Strübing pointed out that sleep was a defining factor in the development of hemoglobinuria. He reasoned that dissolution of red blood cells gradually occurred while the patient slept without causing fever, chills, or flushing and that byproducts of this dissolution were excreted by the kidneys. He hypothesized that the carbon dioxide and lactic acid accumulating from the previous day’s exertion provided the acidic environment required to trigger hemolysis.2

Early History of PNH

Prior to Strübing’s research, several other physicians potentially referenced PNH in their work. 

In 1794, Charles Stewart, a Scottish surgeon, described a 51-year-old Russian patient with “singular periodical discharge of blood from the urethra.”2 

William W. Gull, a British physician, described a case of PNH in a leather worker in 1866; however, he misattributed the symptoms to paroxysmal cold hemoglobinuria, given the patient’s exposure to wet and cold. At the time, paroxysmal cold hemoglobinuria was a clinical entity currently receiving recognition in the literature.2

In 1880, Stolnikow, a Russian physician in St Petersburg, described how the urine of one of his patients accumulated a reddish color overnight; however, he noted a lack of red blood cells and casts in the urine via spectroscopy. He did not accurately characterize the nocturnal pattern of hemoglobinuria because he collected all of his patient’s urine throughout the day in one single specimen.2  

Also in 1880, R. Lepine, a French physician in Lyon, reported a case of PNH that did exhibit the characteristic nocturnal pattern of hemoglobinuria. He also noted the complete absence of erythrocytes in the urine; however, he mentioned that the urine samples contained hemoglobin. He arrived at the conclusion that the disorder was an unusual form of hematuria in which erythrocytes underwent lysis in dilute urine within the renal tubules. Lepine also attributed the majority of cases to the cold, but he pointed out that cold temperatures were not the only trigger, given that his patient experienced lysis at night in bed. He correctly speculated that there must be at least 2 distinct types of paroxysmal hemoglobinuria.2

Following his publications in 1882, Strübing became director of the Nose and Throat Clinic at the University of Greifsvald in 1889, so research on PNH languished until 1911.2,5 

In 1911, the Italian physicians Marchiafava and Nazari described what they believed to be a case of acquired hemolytic anemia, characterized by large quantities of hemosiderin in the urine. Marchiafava described a second case in 1928. Believing he discovered a new clinical disease, he suggested calling it “chronic hemolytic anemia with perpetual hemosiderinuria.”2 

Marchiafava’s student, Micheli, also studied this second patient, proposing that the disease should be called “splenomegalic hemolytic anemia with hemoglobinuria-hemosiderinuria, Marchiafava type.”2,4 

Another Italian physician derived the eponym, Marchiafava-Micheli syndrome, which grew in popularity in the 1930s and 1940s. While the eponym lingered until the 1960s, it did not survive past this time period due to the scant contributions they made to the disease history.2,5 In 1928, Ennekin, a Dutch physician, first coined the current title of the disease: paroxysmal nocturnal hemoglobinuria.5

Also in 1911, the Dutch physician, Hijmans van den Berg, expanded upon Strübing’s research, confirming in vitro that erythrocytes from a patient with PNH underwent hemolysis in an acidic atmosphere containing carbon dioxide, while the erythrocytes of 2 healthy subjects did not undergo hemolysis during the same experiment. The experiments of van den Berg confirmed that PNH is caused by a defect within the erythrocytes as opposed to abnormal factors within the blood plasma, which occurs in paroxysmal cold hemoglobinuria.5 

After additions of fresh human or guinea pig serum failed to restore hemolytic activity to a heat-inactivated serum sample of PNH erythrocytes, van den Berg mistakenly reached the conclusion that erythrocyte hemolysis was not complement-mediated, but caused by the abnormal fragility of erythrocytes to carbon dioxide.5

Read more about PNH etiology

Modern History of PNH

Thomas Hale Ham and John Holmes Dingle, researchers at Case Western Reserve University in the United States, provided evidence in 1939 that the complement pathway mediated erythrocyte hemolysis in patients with PNH.5-7 Ham also developed a highly specific diagnostic test — the acidified serum lysis test (also known as Ham’s test) — which assesses the sensitivity of PNH-affected erythrocytes to lysis by complement.1,5 

Ham also studied the effect of sleep on nocturnal hemoglobinuria, using a Drinker respirator to artificially control respiratory rate and volume in a patient with PNH. During sleep with hyperventilation, hemoglobinuria and hemoglobinemia did not increase. In contrast, sleep without hyperventilation increased acidic pH, which in turn increased hemoglobinuria and hemoglobinemia.5

In 1953, Crosby challenged Ham’s findings when he confirmed that nocturnal hemoglobinuria was not caused by the relative hypoventilation that occurs with sleep. Crosby showed that the acid shift during sleep was not the only pathological mechanism for PNH. Many researchers question the relevance of plasma acidification during sleep, as some patients with PNH do not demonstrate increased hemoglobinemia during sleep.5

In 1954, Pillemer discovered the alternative complement pathway, which demonstrated a hallmark feature that hemolysis no longer occurs after modest serum dilution. This event contrasted with classic complement-mediated lysis, which results in sustained hemolysis despite serum dilutions. This experiment explained why researchers such as van den Berg overlooked complement-mediated hemolysis as an explanation for PNH.5

Read more about PNH pathophysiology

Most Recent History of PNH: Delving Into the Molecular Level

In 1966, Wendell F. Rosse and Professor Dacie at Hammersmith in London devised the complement lysis sensitivity assay, with which they showed that patients with PNH had both normal and abnormal erythrocytes in their blood. It also showed that the essential serum factor for hemolysis was closely associated with a complement of human serum.5,8 

Rosse and Dacie believed that the lytic substance of the serum was a complement; however, later deviation from some of their results related to complement-mediated lytic systems led them to interpret their findings cautiously.5,8 Rosse and Dacie’s seminal studies inspired further research into the pathogenesis of PNH.

In 1973, Logue and colleagues described that PNH-affected erythrocytes bound more complement 3 (C3) than normal erythrocytes when complement was activated by either the classic or alternative pathway.5,9 Following this publication, researchers investigated and detailed the molecular basis of complement-mediated hemolysis of PNH-affected erythrocytes over the next 12 years.5

In 1980, Martin Low and Zilversmit proposed an explanation for the alkaline phosphatase deficiency observed in patients with PNH, suggesting that alkaline phosphatase attaches to the plasma membrane of erythrocytes via a covalent bond to a lipid molecule, phosphatidylinositol.5,10 

Following additional research on erythrocyte membrane proteins during the 1980s, it was proposed that all PNH-affected hematopoietic cells and their progeny lack glycosylphosphatidylinositol (GPI)-anchored proteins.5 

In 1993, Kinoshita and colleagues conducted a series of critical experiments at Osaka University in which they identified the underlying genetic basis of PNH — somatic mutations in the PIGA gene on the X chromosome — causing the GPI-anchor protein deficiency in PNH cells, which prompts complement-mediated hemolysis of PNH-affected erythrocytes.5,11,12  

Read more about PNH clinical trials

References

  1. Hillmen P, Lewis SM, Bessler M, Luzzatto L, Dacie JV. Natural history of paroxysmal nocturnal hemoglobinuria. N Engl J Med. 1995;333(19):1253-1258. doi:10.1056/NEJM199511093331904
  2. Crosby WH. Historical review: paroxysmal nocturnal hemoglobinuria: a classic description by Paul Strübing in 1882, and a bibliography of the disease. Blood. 1951;6(3):270-284. doi:10.1182/blood.V6.3.270.270
  3. Parker CJ. Paroxysmal nocturnal hemoglobinuria: an historical overview. Hematology Am Soc Hematol Educ Program. 2008;2008(1):93-103. doi:10.1182/asheducation-2008.1.93
  4. Wilmanns JC. Paroxysmal nocturnal hemoglobinuria first described in 1882 by Paul Strübing: an example of cooperation between clinical and basic research. Blut. 1982;45(6):367-373. doi:10.1007/BF00320547
  5. Parker CJ. Historical aspects of paroxysmal nocturnal haemoglobinuria: ‘defining the disease’. Br J Haematol. 2002;117(1):3-22. doi:10.1046/j.1365-2141.2002.03374.x
  6. John Holmes Dingle: November 24, 1908-September 15, 1973. In: Biological Memoirs: Volume 61. Washington, DC: National Academies Press; 1992:137-163. doi:10.17226/2037
  7. Ham TH, Dingle JH. Studies on destruction of red blood cells. II. Chronic hemolytic anemia with paroxysmal nocturnal hemoglobinuria: certain immunological aspects of the hemolytic mechanism with special reference to serum complement. J Clin Invest. 1939;18(6):657-672. doi:10.1172/JCI101081
  8. Rosse WF, Dacie JV. Immune lysis of normal human and paroxysmal nocturnal hemoglobinuria (PNH) red blood cells. I. The sensitivity of PNH red cells to lysis by complement and specific antibody. J Clin Invest. 1966;45(5):736-748. doi:10.1172/JCI105388
  9. Logue GL, Rosse WF, Adams JP. Mechanisms of immune lysis of red blood cells in vitro. I. Paroxysmal nocturnal hemoglobinuria cells. J Clin Invest. 1973;52(5):1129-1137. doi:10.1172/JCI107279
  10. Low MG, Zilversmit DB. Role of phosphatidylinositol in attachment of alkaline phosphatase to membranes. Biochemistry. 1980;19(17):3913-3918. doi:10.1021/bi00558a004
  11. Miyata T, Takeda J, Iida Y, et al. The cloning of PIG-A, a component in the early step of GPI-anchor biosynthesis. Science. 1993;259(5099):1318-1320. doi:10.1126/science.7680492
  12. Takeda J, Miyata T, Kawagoe K, et al. Deficiency of the GPI anchor caused by a somatic mutation of the PIG-A gene in paroxysmal nocturnal hemoglobinuria. Cell. 1993;73(4):703-711. doi:10.1016/0092-8674(93)90250-t

Reviewed by Debjyoti Talukdar, MD, on 11/30/2022.

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