Hereditary Disorders-autosomal recessive diseasex

cystic fibrosis-H.hemochromatosis-carbamyle phosphate synthase def.-cong.adrenal hyperplasia-alkaptonuria-cystinosis-cystinuria-Fncone anemia-Dubin-Jhonson dis.-Fmilial medeterranian fever...

1. HEREDITARY DISEASES Ekbal Mohamed Abo Hashem .MD Professor of Clinical Pathology Faculty of Medicine Mansoura University-EGYPT 1-Autosomal Recessive Diseases

2. AUTOSOMAL RECESSIVE DISEASES An individual with an autosomal recessive disease has inher­ited two abnormal alleles at a given locus by receiving one mutant allele from each carrier parent, and the disease ­causing gene is on one of the autosomes (1 to 22) and not a sex chromosomes (X or Y).

3. The affected patient may be homozygous for a specific mutation by receiving the same mutation from each parent or may be a compound heterozygote having received a different mutation within the gene from each parent. Regardless of the mechanism, the end result is the same; the patient has no normal allele

4. Abetalipoproteinemia Acute fatty liver of pregnancy Alkaptonuria Carpenter syndrome Chediak -Higashi syndrome Chondrodystrophy CAH Fanconi anemia Congenital hepatic fibrosis Cystic Fibrosis Hereditary hemochromatosis Carbamyl phosphate synthetase deficiency Cystinosis , Cystinuria Dubin -Johnson syndrome Familial Mediterranean Fever List of autosomal recessive diseases:

5. Gastroschisis Gaucher’s disease Glanzman’s Thromasthenia Glycogen storage diseases Hartnup Disease Leukocyte Adhesion Defect Nieman Pick Disease Rotor syndrome Situs Inversus Sickle cell Disease and Trait Tay -Sachs Thalasemia Werner syndrome Wilson’s Disease Xeroderma pigmentosa List of autosomal recessive diseases (cont.)

6. 1. Cystic Fibrosis a. Phenotypic Expression CF is a multisystem disorder affecting the pulmonary, gas­trointestinal, and reproductive organs. However, the pheno­typic expression of the disease is heterogeneous, ranging from meconium ileus and severe respiratory disease in infants to mild pulmonary symptoms and no evidence of gastrointestinal problems even in adulthood.

7. Cystic Fibrosis(cont.)

8. Cystic Fibrosis(cont.)

9. Cystic Fibrosis(cont.)

10. Cystic Fibrosis(cont.)

11. Morbidity and mortality of the disease are most related to mucus accumu­lation; recurrent infections with unusual pathogens, such as Pseudomonas aeruginosa; and excessive inflammation in the lung. Cystic Fibrosis(cont.) The gene was mapped to 7q31 (long arm of chromosome 7, banding region 31). It codes for the CF transmembrane conductance regulator protein (CFTR) of 1480 amino acids. The molecule is located within the lipid bilayer, predominantly at the apical mem­brane of secretory epithelial cells where it serves as a cyclic adenosine monophosphate (cAMP)-activated chloride ion channel to regulate chloride ion conductance.

12. In addition to chloride conductance, the molecule is involved in trans­port of sodium, potassium, and ATP from the intracellular compartment to the extracellular surface. A routine sweat chloride concentration determination is considered necessary for the diagnosis of CF (>60 mmol /L in childhood; >40mmol/L older than 15 years), although some patients with CFTR mutations may have borderline or even normal results. Cystic Fibrosis(cont.)

13. Cystic Fibrosis(cont.)

14. Some patients may have only congenital bilateral absence of the vas deferens (CBAVD), pancreatitis, pulmonary disease, or nasal polyps. Thus although the diagnosis of CF can easily be made in patients with characteristic clinical features and abnormal sweat chloride concentrations, in patients with atypical presenta­tion, mutations in the CFTR gene cannot be excluded without complete sequence analysis of the gene. Cystic Fibrosis(cont.)

15. Since CF is an autosomal recessive disorder, the CF patient must have two mutant CFTR alleles to develop the disease. Patients will be homozygous with two copies of the same mutation or will represent a compound heterozygote with one copy of one mutation and one copy of a second mutation. Cystic Fibrosis(cont.) c. Mutant alleles

16. Although the type and location of the mutation vary in their effect on CFTR and ultimately affect the phenotype of the patient, environmental factors and less characterized modifier genes also appear to be important in modulating the CF disease phenotype. The CFTR genotype and clinical phenotype are most closely related for pancreatic involvement and least closely related for pulmonary manifestations of the disease. Cystic Fibrosis (cont.)

17. Mutations can be divided into five classes : Patients with class 1 mutations have defects in protein production class 2 mutations are asso­ciated with defective processing of CFTR. In both cases, CFTR trafficking to the cell membrane does not occur, and both class 1 and class 2 mutations are typically associated with a severe phenotype. Cystic Fibrosis(cont.)

18. Class 3 and 4 mutations have CFTR expression at the cell membrane, but channel activity is reduced. Class 3 mutations can be associated with a more severe phenotype and result from defective regulation Class 4 mutations can be mild and result from defective con­duction. Cystic Fibrosis(cont.) d. Mutation Classes(cont.)

19. Class 5 mutations are associated with abnormal splicing of the CFTR messenger ribonucleic acid (mRNA) and may be associated with a severe phenotype (621 + 1 G> T) or a mild phenotype (2789 + 5G>A). Cystic Fibrosis(cont.) Mutation Classes(cont.)

20. The most common mutation, deltaF508, seen in Caucasians of Northern European descent, affects processing of CFTR and prevents its trafficking to the apical membrane. Prevalent mutations G542X and W 1282X cause premature translation termination and thus truncation of the protein. The frequently observed muta­tion G551 D results in CFTR that reaches the apical membrane but that improperly regulates the chloride channel. Cystic Fibrosis(cont.) Mutation Classes(cont.)

21. Cystic Fibrosis(cont.) Mutation Classes(cont.)

22. To confirm the diagnosis of disease in patients with equivocal sweat chloride results or in instances when insufficient material is collected. Alternatively, in the known CF patient, mutation analysis can be requested to help predict the prognosis since some genotype-phenotype cor­relations exist. Cystic Fibrosis(cont.) e. DNA Testing

23. Identifying the mutations segregating in a family enables preimplantation diagnosis or prenatal testing for subsequent pregnancies and carrier or diagnostic testing for other at-risk family members. Cystic Fibrosis(cont.) DNA Testing(cont.) Genetic testing and early diagnosis and intervention of patients has been associated with reduced severity of lung disease and increased survival

24. Hereditary hemochromatosis (HH) is an autosomal reces­sive disorder of iron regulation that can result in excess iron deposition in otherwise healthy tissue. Affected individuals can absorb approximately 3 to 4 mg of iron per day com­pared with the normal rate of 1 to 2 mg per day. 2. Hereditary Hemochromatosis a. Inheritance and Phenotypic Expression

25. Symptoms associated with this disease occur during mid to late adult­hood, but the diagnosis of HH is often delayed, because the early symptoms of weakness, lethargy, joint pain, and abdominal pain are nonspecific. Hereditary Hemochromatosis(cont.) Inheritance and Phenotypic Expression(cont.)

26. Complications of the disease include hepatic cirrhosis, diabetes mellitus, hypopi­tuitarism, hypogonadism , arthritis, and cardiomyopa­thy. The incidence of the disease is estimated to be about 1 in 200 to 400, making HH one of the most common genetic disorders known. Hereditary Hemochromatosis(cont.) Inheritance and Phenotypic Expression(cont.)

27. However, the phenotypic expres­sion of the disease is dependent on other genetic and envi­ronmental factors. The disease is more common in men than women presumably because of the protective effect of iron loss during menstruation and pregnancy. Hereditary Hemochromatosis(cont.) Inheritance and Phenotypic Expression(cont.)

28. In addition, although regular blood donation is protective against HH, increased alcohol consumption, dietary iron, or vitamin C, an enhancer of iron uptake, increases the likelihood of symp­toms in the presence of an affected genotype. Hereditary Hemochromatosis (cont.) Inheritance and Phenotypic Expression(cont.)

29. Laboratory testing for hemochromatosis most often includes Determi­nation of transferrin saturation [(serum iron/total iron binding capacity) x 100] with a satura­tion >55% to 60% considered abnormal for men, >45% to 50% abnormal for women, Serum ferritin > 400ng/mL abnormal for men, and >200ng/mL abnormal for women. Hereditary Hemochromatosis(cont.) Inheritance and Phenotypic Expression (cont.) These tests may be ordered singly or in combination.

30. Subsequently a liver biopsy often follows to determine the amount of stainable iron and the degree of injury. Management of the disease includes therapeutic phlebotomy and dietary avoidance of medicinal iron, mineral supplements, excess vitamin C, and uncooked seafoods . Hereditary Hemochromatosis(cont.) Inheritance and Phenotypic Expression(cont.)

31. An association of human leukocyte antigen (HLA)-A3 and HLA-BI4 antigens with idiopathic hemochromatosis was reported, which suggested that the HH gene was located near the major histocompatibility complex (MHC) on chromosome 6p (short arm of chromosome 6). Hereditary Hemochromatosis(cont.) b. HLA Association :

32. Classic genetic studies confirmed linkage of the HH gene to the HLA locus, and in 1996 the HH gene, HFE was cloned . Although HFE remains the primary gene associated with hemochromatosis, other genes have been mapped or cloned that are associated with dominantly inherited hemochromatosis (SLCllA3, ferroportin1, and H-­ferritin) and with juvenile and rare autosomal recessive (TFR2) forms of hemochromatosis. Hereditary Hemochromatosis(cont.) HLA Association(cont.)

33. The HFE gene protein, HFE, encodes a  2-microglobulin­ associated protein with structural resemblance to MHC class I proteins. The HFE gene contains seven exons spanning about 12 kb, and the 4.1 kb mRNA is widely expressed with some suggestion of higher expression in the liver and intestine, major sites of iron metabolism in the body, and to a lesser degree in the brain. Normal HFE binds to the transferrin receptor and reduces its affinity for iron-loaded transferrin. Hereditary Hemochromatosis(cont.) c. HFE Gene Protein :

34. Interestingly, although HFE is widely expressed in the gastrointestinal tract, the most abundant immunohistochemical staining for the protein is in the crypt enterocytes, where it has a distinct intracellular localization suggesting that its function is to sense the level of body iron stores and regulate, rather than directly participate in, iron absorption. 2. Hereditary Hemochromatosis c. HFE Gene Protein Hereditary Hemochromatosis(cont.) HFE Gene Protein(cont.)

35. Hereditary Hemochromatosis(cont.) i ) A founder effect, suggested by linkage disequilibrium between HLA haplotypes and the HFE gene, was confirmed by the identification of homozygosity for a common mutation, G-to-A base pair substitution, in HH patients. d. Gene Mutations:

36. This mutation results in a cysteine-to-tyrosine substitution at amino acid 282 (C282Y) in HFE and disrupts disulfide bridges required for normal interaction with  2 microglob­ulin on the cell surface and allows for high-affinity transfer­rin binding to the uncomplexed transferrin receptor. Hereditary Hemochromatosis (cont.)

37. ii) A second base substitution of C-to-G in exon 2 and resulting in a histidine (H) to aspartic acid (D) substitution at codon 63 (H63D) has been identified in a higher per­centage of C282Y-negative HH patients than would be expected based on the frequency of this mutation in the pop­ulation. Hereditary Hemochromatosis(cont.)

38. Hereditary Hemochromatosis(cont.)

39. HFE, with this alteration, is expressed at the cell surface, but its interaction with the transferrin receptor is altered, resulting in more iron deposition within the cell. Mutation H63D is associated with an increased risk of developing a mild form of hemochromatosis. Hereditary Hemochromatosis(cont.)

40. iii) A third common mutation in the HFE gene has been reported that is associated with a mild form of hemochromatosis. This A-to- T mutation results in a serine-to-cysteine substitution at codon 65 (S65C) in exon 2 and is in close proximity in the gene to the previously described H63D mutation. Hereditary Hemochromatosis(cont.)

41. DNA analysis of the HFE gene is done using a variety of methodologies and in most laboratories includes testing for mutations C282Y and H63D. Once HFE muta­tion analysis has confirmed the cause of HH in the patient, transferrin saturation (TS), serum ferritin, and DNA testing of at-risk family members can identify those who may benefit from earlier treatment and dietary restrictions. e. DNA Testing Hereditary Hemochromatosis (cont.)

42. Hereditary Hemochromatosis (cont.)

43. Hereditary Hemochromatosis(cont.)

44. Hereditary Hemochromatosis(cont.)

45. Hereditary Hemochromatosis(cont.)

46. Hereditary Hemochromatosis(cont.)

47. 3. Carbamyl Phosphate Synthetase I Deficiency

48. CPSI catalyzes the first step of the urea cycle by converting ammonia and bicar­bonate to carbamyl phosphate. Through a series of enzy­matic reactions, the toxic ammonia molecule is converted to the nontoxic water-soluble urea containing two amino groups, which is excreted as urine. In the absence of CPSI or any of the other urea cycle enzymes, a hyperammonemic crisis ensues, and associated neurological tissue destruction and/or death occurs. Carbamyl Phosphate Synthetase I Deficiency(cont.)

49. Carbamyl Phosphate Synthetase I Deficiency(cont.)

50. Carbamyl Phosphate Synthetase I Deficiency (cont.)

51. The affected newborn appears clinically normal but within the first 24 to 72 hours develops vomiting and lethargy, and as blood ammonia levels continue to rise, coma and death are immi­nent unless treatment is initiated immediately.   Carbamyl Phosphate Synthetase I Deficiency(cont.)

52. Labora­tory findings include increased plasma ammonia; low plasma urea; decreased or absent plasma citrulline and arginine-normal urine orotic acid; and normal urine organic acids. The diagnosis is confirmed by a liver biopsy for mea­surement of CPSI activity.   Carbamyl Phosphate Synthetase I Deficiency (cont.)

53. In most patients, CPSI enzyme activity less than 20% of controls is consistent with CPSI deficiency, and activity less than 5% results in neonatal presentation. However, a few patients have been reported with partial CPSI activity that was associated with late or adult presentation. Carbamyl Phosphate Synthetase I Deficiency (cont.)

54. The chronic phase of the disease is treated with a nitrogen-restricted diet, citrulline , and chronic sodium phenylbutyrate to reduce the blood ammonia. Management of this urea cycle disorder is complex and is most effective with immediate intervention and a multidis­ciplinary effort. Liver transplantation can be an effective form of treatment. Carbamyl Phosphate Synthetase I Deficiency (cont.)

55. The CPSI gene is mapped to 2q35, spans 120 kb, com­prises 38 exons, and consists of a 123 nucleotide 5' -untrans­lated region, an open reading frame of 4500 nucleotides, and 1123 nucleotides in the 3'-untranslated region. Exons range in size from 56 to 260 bp in length, and introns range from 415 to 21,160 bp. Carbamyl Phosphate Synthetase I Deficiency(cont.) b. CPSI Gene

56. The CPSI gene encodes a 165 kD proenzyme that is transported into the mitochondria, where it is cleaved into the functional 160 kD form. CPSI is present in the mitochondrial matrix of hepatocytes and epithelial cells of the intestinal mucosa. Carbamyl Phosphate Synthetase I Deficiency(cont.)

57. CPSI deficiency represents a rare dis­order with no common mutations. Rather, heterogeneous mutations throughout the gene have been described including missense, deletion, insertion, and splicing mutations. Heterogeneous mutations for a rare disease make clinical testing for CPSI deficiency challenging. Carbamyl Phosphate Synthetase I Deficiency(cont.) c. Gene Mutation

58. DNA specimens are collected from the parents and the affected child. If the affected child died before col­lection of a peripheral blood sample, paraffin-embedded autopsy material can be submitted for analysis. d. DNA Testing Carbamyl Phosphate Synthetase I Deficiency (cont.)

59. When the family ultimately requests future prenatal testing, either chorionic villus tissue or cultured chorionic villus tissue or amniocytes from the fetus are submitted for analysis. Within a few days, the fetal DNA is tested with the DNA markers for which the family is informative, and a diagnosis regarding the CPSI deficiency of the fetus is known. In most instances, the accuracy of the results approaches 99%. Carbamyl Phosphate Synthetase I Deficiency(cont.)

60. Sickle cell anemia is one of the most common, inherited, single-gene disorders in African-Americans.. Sickle cell disease involves the red blood cells, or hemoglobin , and their ability to carry oxygen. Normal hemoglobin cells are smooth, round, and flexible, like the letter "O." They can easily move through the blood vessels. 4 . Sickle cell anemia

61. Sickle cell hemoglobin cells are stiff and sticky. When they lose their oxygen, they form into the shape of a sickle, or the letter "C." These sickle cells tend to cluster together and cannot easily move through the blood vessels. The cluster causes a blockage and stops the movement of healthy, normal, oxygen-carrying blood. This blockage is what causes the painful and damaging complications of sickle cell disease .

62. Carbamyl phosphate synthetase I (CPSI) deficiency is an autosomal recessive inborn error of metabolism. The frequency of the disease may actually be higher in regions of the world with a higher percentage of consanguineous matings , and reported frequencies do not account for the undiagnosed neonates that die in the first few days of life. Carbamyl Phosphate Synthetase I Deficiency (cont.) a. Phenotype

63. Linus Pauling –in late 1940s - discovered that the hemoglobin from sickle cell anemia patients had an abnormal electrophoretic mobility, indicating that its structure was different from that of normal hemoglobin . Moreover, Pauling found that healthy relatives of these patients often had a 50:50 mixture of the normal and abnormal hemoglobins . In 1957, Vernon Ingram showed that hemoglobin ( Hb ) S was identical to normal Hb A except for the replacement of glutamic acid, the sixth amino acid in beta (β)-globin, with valine . This was the first demonstration of a human disease arising from a single structural mutation. Historical background :

64. Hemoglobin S (Hb S) is the most widely distributed structural hemoglobin (Hb) variant and results from the substitution of valine for glutamic acid in the 6th amino acid in the β-globin chain. This leads to reduced solubility of the Hb molecule especially in a deoxygenated medium with the formation of polymers, which distort the red blood cell (RBC) membrane causing rigidity and less deformability of the cell.

65. In addition, there is reduced life span of the RBC. Homozygotes or compound heterozygotes (Sβ 0 thal , SC, etc.) have sickle cell disease (SCD), which is characterized by recurrent vaso -occlusion with consequent body pains, chronic hemolysis and end-organ damage.

66. Sickle cell trait describes a condition in which a person has one abnormal allele of the hemoglobin beta gene (is heterozygous ), but does not display the severe symptoms of sickle cell disease that occur in a person who has two copies of that allele (is homozygous ). Those who are heterozygous for the sickle cell allele produce both normal and abnormal hemoglobin (the two alleles are codominant with respect to the actual concentration of hemoglobin in the circulating cells)

67. The molecular characteristics of the disease show several linkage disequilibrium restriction fragment length polymorphisms in the β-globin gene cluster that define the four major haplotypes associated with the β S locus . These are the Benin, Senegal, Bantu and Arab-Indian haplotypes .

68. Clinical research has demonstrated the influence of haplotypes in the phenotype such that Senegal and Arabian/Indian haplotypes are associated with the mildest course. Patients with these two haplotypes have elevated Hb F, which has also been shown to, independently, ameliorate clinical course because it improves solubility of the Hb S molecule, reduces polymerization and anemia .

69. The pathophysiology of the disease shows a process of gelation, and Hb S polymerization. Essentially, with deoxygenation there is a critical delay time before polymerization commences with an initial nucleus followed by rapid extension .. Significant rheological changes ensue with increased viscosity, which promotes vaso -occlusion and thrombotic phenomena. Several other factors including pH, O2 tension, temperature and the RBC 2,3-diphosphoglycerate levels all influence the rate of gelation with implications for potential therapeutic interventions .

70. Two major phenotypes of SCD have been recognized: The first is recurrent vaso -occlusion due to different models of gelation and rheological abnormalities ,and the second type is hemolysis . Another model of SCD pathophysiology has been proposed that involves the interaction of hemolysis and the endothelium . It is now recognized that SCD is a chronic inflammatory state with extensive oxidative stress involving several enzyme systems and isch emia/reperfusion injury, with nitric oxide (NO) dysregulation playing a central role.

71. Progression of vaso -occlusion by sickle cells

72. Following hemolysis , an intense inflammatory response occurs with eventual NO depletion. NO is a critical endogenous vasodilator synthesized by endothelial cells from its obligate substrate L -arginine, which is converted to citrulline by NO synthases. SCD is characterized by a state of NO resistance, inactivation and impaired availability with consequent vasoconstriction, platelet activation, up-regulation of adhesion molecules, thrombin generation and endothelial intima proliferation culminating in arterial stenosis and eventual occlusion.

73. The release of arginase from the lysed RBCs reduces available arginine by redirecting its metabolism to ornithine (instead of citrulline and NO), with the formation of polyamines and proline, which promote smooth muscle proliferation and collagen synthesis .

74. pulmonary hypertension, stroke,priapism and leg ulcers. The biomarkers of this process include free plasma hemoglobin, arginase , reticulocyte count, serum lactate dehydrogenase and bilirubin. The risk of pulmonary hypertension, i.e. a tricuspid regurgitant velocity of ≥ 2.5 m/s, is currently the strongest predictor of early death in adult SCD patients . The sub -phenotypes of SCD which are directly attributable to heamolysis and endothelial dysfunction include :

75. Many other genetic factors modify the course of the disease. While Hb F and a coexistent α- thal trait are recognized as the major ameliorating factors, several single nucleotide polymorphisms in gene loci both within the β-globin gene cluster on chromosome 11 and in other chromosomes are being increasingly identified modifiers . However, these genetic mechanisms do not adequately explain the phenotypic diversity of the disease. Epigenetic and environmental mechanisms are also quite important .

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