Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0000737 (abdominal pain)
 31,184 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic blood disease. The dramatic symptoms that gave the disease its name and the unique nature of the underlying cellular abnormality made the disease for many years a curiosity amongst human blood disorders. Clinical manifestations of PNH are chronic hemolytic anemia with acute exacerbations, bone marrow failure, an increased tendency to thrombosis, and episodes of severe abdominal pain. PNH has a close although not yet fully understood relationship to aplastic anemia (AA), and probably also to acute myeloid leukemia (AML). Blood cells in patients with PNH have a defect in the biosynthesis of a complex glycolipid structure which is a glycosyl phosphatidylinositol (GPI) molecule and serves as an anchor for many surface proteins. Red cells, granulocytes, monocytes, lymphocytes and platelets are therefore deficient in all proteins which are anchored to the cell membrane by such a molecule. Biochemical analysis pinpointed the metabolic block in PNH cells to an early step in the anchor biosynthesis. The block in the biosynthetic pathway is due to the deficiency of a protein called PIG-A. The PIG-A gene maps to the X-chromosome. Cloning of the gene and analysis of the gene in PNH patients lead to the identification of a number of somatic mutations which occur on the active X-chromosome in an early hematopoietic stem cell. All mutations identified thus far inactivate or impair the function of the PIG-A protein and therefore fully explain the deficiency of the missing surface proteins, which in turn explain some of the clinical features of the disease. However, the characterization of the molecular lesion does not explain how the PNH clone can expand to the extent of contributing a substantial proportion of the patient's hematopoiesis. Thus a second factor is needed to explain the pathogenesis of PNH. We hypothesize that this is most likely the coexistence of bone marrow failure that produces paradoxically a growth or survival advantage for the PNH clone. The coexistence of more than one PNH clone in many patients supports this hypothesis and suggests that bone marrow failure is the primary event. The occurrence of the PIG-A mutation causing the absence of GPI-linked proteins on blood cells allows the PNH clone to flourish and to maintain hematopoiesis; thus it seems that the PIG-A mutation is nature's own gene therapy and the price that these patients have to pay is PNH.
 ...
PMID:Paroxysmal nocturnal hemoglobinuria: the price for a chance. 894 96

PNH is an uncommon acquired hemolytic anemia that often manifests with hemoglobinuria, abdominal pain, smooth muscle dystonias, fatigue, and thrombosis. The disease results from the expansion of hematopoietic stem cells harboring a mutation in a gene, PIG-A, that is required for the biosynthesis of a lipid moiety, glycosylphosphatidylinositol (GPI), that attaches dozens of different proteins to the cell surface. Thus, PNH cells are deficient in cell surface GPI anchored proteins; this deficiency on erythrocytes leads to intravascular hemolysis since certain GPI anchored proteins normally function as complement regulators. Free hemoglobin released from intravascular hemolysis leads to circulating nitric oxide depletion and is responsible for many of the clinical manifestations of PNH, including fatigue, erectile dysfunction, esophageal spasm, and thrombosis. Interestingly, rare PIG-A mutations can be found in virtually all healthy control subjects leading to speculation that PIG-A mutations in hematopoietic stem cells are common benign events. However, recent data reveals that most of these mutations in healthy controls are not derived from stem cells. The recently FDA approved complement inhibitor eculizumab has been shown to decrease hemolysis, decrease erythrocyte transfusion requirements, decrease the risk for thrombosis and improve quality of life for PNH patients.
 ...
PMID:Advances in the diagnosis and therapy of paroxysmal nocturnal hemoglobinuria. 1806 59

The understanding of the clinical manifestations in paroxysmal nocturnal haemoglobinuria (PNH) has made great progress. The main symptoms of this disease such as abdominal pain, renal failure or pulmonary hypertension and even the basis of the dramatic thrombophilia can be related to intravascular haemolysis and liberation of free haemoglobin resulting in NO depletion. In addition, there has been a recent great progress in elucidating the pathophysiology of clonal expansion within PNH bone marrow. In the majority of patients with haemolytic PNH, there are additional mutations within genes beyond PIG-A and rather affecting growth and differentiation of clonal bone marrow cells. In contrast to the formerly proposed single mechanism hypotheses such as immune selection or intrinsic gain of clonal dominance, this appears to follow a pattern of a complex clonal hierarchy putatively integrating both earlier anticipated mechanisms. Treatment of PNH is mainly supportive. The only curative approach as allogeneic stem cell transplantation should only be applied to patients with complications such as secondary bone marrow aplasia or transformation into MDS or AML. Symptomatic haemolytic PNH will be treated with eculizumab, an inhibitor of the terminal complement cascade. Treatment with eculizumab can significantly prevent PNH-related symptoms including the abnormal thrombophilia. Recently, it was demonstrated that in contrast to untreated historic PNH patients, meanwhile a normal life expectancy is observed in eculizumab-treated patients. The recently approved vaccine against meningococci type B by the European Medical Agency (EMA) could probably further help to prevent meningococcal sepsis due to the induced complement deficiency by eculizumab.
...
PMID:Update on paroxysmal nocturnal haemoglobinuria: on the long way to understand the principles of the disease. 2570 78