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General Pathology > Genetic and developmental disorders > Flashcards

Genetic and developmental disorders Flashcards

0
Q

Primary germ layers

A

Fetal organs and tissues including muscle, bone, nervous tissue, develop from primary germ layers

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1
Q

Normal embryonic development

A

Fertilization between egg and sperm yields zygote
Zygote cells divide to form morula
Morula transforms into blastocyst
Inner cell mass gives rise to primordial germ layers: ectoderm, endoderm, mesoderm

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2
Q

critical stage of organogenesis

A

Characterized by extensive cell division, migration and cell-to cell interaction
Developing organs very sensitive to external influences
Include most importantly chemical, physical and viral agents

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3
Q

Teratology

A

Disturbance in development

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4
Q

Teratogen

A

Causes fetal abnormalities. 75% cases idiopathic, 20 % genetic

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5
Q

Exogenous teratogens - physical

A

X-rays

Radiation- gamma, beta, alpha rays

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6
Q

Exogenous teratogens - chemical

A

Many man made and many exists in nature

most important - alcohol

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7
Q

Exogenous teratogens - Alcohol

A

Can result in Fetal Alcohol Syndrome (FAS)
Causes intrauterine growth retardation
Affects development of brain
Typical facial features include small cranium and jaw, thin upper lip
Reduced mental processes, low IQ

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8
Q

Exogenous Teratogens - Microbial teratogens

A

Can affect fetus directly or indirectly
Indirectly effects from weakening or exhausting of mother causes decrease in fetal weight, growth retardation, premature birth
Human pathogens that are especially noxious to fetus include Torch

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9
Q

Exogenous Teratogens - TORCH

A

Toxoplasma, Others (Epstein-Barr Virus, Varicella virus, etc), Rubella, Cytomegalovirus (CMV), Herpes Simples

Several internal organs can be affected including the brain
All symptoms related to transplacental passage of infectious agent during organogenesis

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10
Q

TORCH - R

A

Rubella: Brain is small (Microcephaly) and often structurally abnormal: heart defects, inflammation of liver, lungs, enlarged spleen and lymph nodes, eye anormalies

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11
Q

TORCH - T and C

A

Toxoplasmosis and Cytomegalovirus (CMV)

Characteristic abnormalities in brain, small eyes with inflammation, cataracts and calcifications

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12
Q

TORCH - H

A

Herpes virus - skin lesions

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13
Q

Endogenous teratogens - G

A

Genetic factors
Often fetus is not viable resulting in spontaneous abortions (miscarriage)
Other examples include cleft lip, dwarfism, etc

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14
Q

Chromosomal normalities

A

Human genes encoded by triples of nucleotides. Double-helix DNA condense into chromosomes during meiosis. Normal human cells contain 23 chromosome pairs - 22 autosomes and 2 sex chromosomes (XY male, XX females)

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15
Q

Chromosomal abormalities

A 
Structural 
or
Numerical ->trisomy (+1) or monosomy (-1)
and 
autosomes
or Sex chromosomes (XX, XY)
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16
Q

Trisomy 21

A

Down’s Syndrome
translocation or three autosome 21
Diagnosed in 1/800 babies, mostly maternal origin as causing infertility in males

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17
Q

Down’s syndrome S&S

A

Mental retardation
Typical facial features - wide face, low-bridged nose, close set slanted eyes, large protruding tongue
Abnormal extremities - short arms and legs, wide hands, “simian crease”, short and crooked fifth finger
Defects of internal organs - heart defects, infertility in males
Hematologic abnormalities - anemia, leukemia, immune deficiencies
Increased mortality
No cure

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18
Q

Down’s syndrome Diagnosis

A

Chorionic villus biopsy

Amniocentesis

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19
Q

Abnormalities of sex chromosomes

A

More common than autosomes

Less lethal, less miscarriage

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20
Q

Turner’s syndrome

A

Monosomy X (45, X)
Affects 1/3000 newborns
Short stature, webbing of neck, abnormal extremities, broad chest, congenital heart disease
Normal female genital organs except for ovaries which do not develop normally hypoplastic uterus, amenorrhea,
Never experience puberty
Do not develop secondary sex characteristics,
Infertile
Sex hormone therapy always female

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21
Q

Klinefelter’s Syndrome

A

47, XXY
Infertile males
Testis are atrophic and unable to produce sperm
Secondary sex characteristics do not develop at puberty
Penis is small and pubic hair is scant
Tall, effeminate, gynecomastia

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22
Q

Autosomal dominant diseases affect Connective Tissue

A

Marfan’s syndrome

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23
Q

Autosomal dominant disease affects bones

A

Achondroplastic dwarfism, Osteogenesis imperfecta

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24
Q

Autosomal dominant disease affect cardiovascular system

A

Familial hypercholesterolemia

25
Q

Autosomal dominant disease affect kidney

A

Adult polycystic kidney disease, Wilms’ tumor

26
Q

Autosomal dominant disease affects Hematopoietic system

A

Spherocytosis

27
Q

Autosomal dominant disease affects gastrointestinal system

A

Familial polyposis coli

28
Q

Marfan’s syndrome

A

Autosomal dominant disease, 25% spontaneous mutation
Affects 1/10,000 persons
Multisystemic disease
Skeletal change - slender skeleton, elongated head, joints are loose, ligaments are weak, laxations, spinal deformities
Cardiovascular changes - CT of large vessels is weak leading to aneurysms; faulty heat valves lead to heart failure
Ocular changes - subluxated lens, cataracts, retinal detachment, blindness
Pathogenesis related to defect in gene that codes for fibrillin

29
Q

Familial Hypercholesterolemia

A

Autosomal dominant
1/500 persons affected in US
Common cause of cardiovascular disease
Caused by mutation in gene encoding the receptor for low-density lipoprotein (LDL), transports cholesterol
Receptor deficiency - LDL cholesterol removal from blood is less efficient
Leads to deposition of lipids in arteries (“clogged arteries”) leading to cardiovascular disease
Xanthomas - lipid-rich yellow nodules; consist of macrophages that have phagocytized cholesterol
No cure
Progression of disease can be slowed by low fat diet and drugs

30
Q

Autosomal dominant disease affects Nervous system

A

Huntington’s disease

Neurofibromatosis

31
Q

Autosomal recessive disorders

A

Encoded by genes located on one of the 22 autosomes
only expressed under homozygous conditions
Only expressed if one gene inherited from each parent
parents are usually asymptomatic carriers

32
Q

Autosomal recessive disorder affects exocrine glands

A

Cystic fibrosis

33
Q

Autosomal recessive disorders of anemias

A

Sickle cell anemia

Thalassemia

34
Q

Autosomal recessive disorders of mucopolysaccharidoses

A

Hurler’s syndrome

Hunter’s syndrome

35
Q

Autosomal recessive disorder of lipidoses

A

Tay-sachs disease

Niemann-pick disease

36
Q

Autosomal recessive disorders amino acid disorders

A

Phenylketonuria

Albinism

37
Q

Cystic fibrosis (CF)

A

Most common autosomal recessive disorder in US
1/2500 neonates in US
1/25 person estimated carrier
Almost exclusively seen in whites
Affected gene codes for chloride transport channel in cell membrane

38
Q

Cystic Fibrosis Pathogenesis

A

Leads to lack of NaCl in glandular secretions in all exocrine glands,
Leads to less water in secretions - more viscous
Viscous mucous leads to obstruction of organs
Obstruction in pancreas - enzymes don’t flow into intestine
Leads to malabsorption of nutrients
stools are bulky, greasy and malodorous
Children often slow growth retardation
Most important complication involves bronchial mucosa
bronchial mucous plugs prevent normal respiration

Mucous provides fertile growth medium for bacteria
Affected individual presents with recurrent bacterial infections, chronic bronchitis, recurrent pneumonia,
Sweat glands are affected (salty)
males often infertile
no cure

39
Q

Lysosomal storage diseases

A

Related to deficiency of enzymes involved in intermediary metabolism
Metabolites that cannot be fully degraded, digested or incorporated get stored in lysosomes

Lysosomal storage diseases classified based on primary pathway affected; or on eponyms (named after) e.g. lipidoses, glycogenoses, mucopolysaccharidoses, Tay-Sachs, etc.
Tay-Sachs is a defect in the function of hexosaminidase A resulting in accumulation of ganglioside (neuro)
All LSDs characterized by accumulation of metabolites that cannot be processed due to inherited gene defect

40
Q

Lysosomal Storage Diseases S&S and DX

A

Symptoms are variable
Cam be mild or lethal
Include splenomegaly, anemia, deformities, neurologic symptoms, etc.
Diagnosis can be done in utero

41
Q

Phenylketonuria (PKU)

A

Autosomal recessive disease.
Congenital defect of phenylalanine hydroxylase (PAH), an enzyme that metabolizes phenylalanine into tyrosine

Phenylalanine ingested from food cannot be metabolized and accumulates in blood and tissues

Phenylalanine also gets converted into phenylpyruvic acid and phenylketones which get excreted in urine

42
Q

Phenylketonuria Dx and Tx

A

Children born with PKU initially healthy
Diagnosis done at birth by mandatory routine screening
Special phenylalanine free diet prescribed will ensure normal neural development
Normal diet results in slow, progressive, irreversible mental retardation

43
Q

X-linked recessive disorders

A

Encoded by recessive genes located on X but not Y chromosome
Rarely expressed in females
Gene is transmitted from asymptomatic mother
Examples include
hemophilia
muscular dystrophy (Duchenne’s, Becker’s)
Congenital immunodeficiencies (Agammaglobulinemia, Wiskott-Aldrich syndrome, X-linked immunodeficiency, Lymphoproliferative disorders)

44
Q

Hemophilia

A

X-linked Recessive disease
Hereditary bleeding disorder linked to mutations of genes that code for:
Coagulation factor VIII (hemophilia A)
-Affects 1/5000 boys
-Mild to severe symptoms depending on extent of defect
-Asymptomatic or severe bleeding disorder

Coagulation factor IX (hemophilia B)
-Always severe bleeding disorder

Hemophilia A and B

  • Internal hemorrhage common
  • Deformity of joint common
  • Hemorrhage may be spontaneous or follow minor trauma
45
Q

Hemophilia treatment

A

Includes blood transfusions and administration of deficient clotting factors

46
Q

Muscular Dystrophy (MD)

A

Characterized by progressive wasting of muscles
Linked to a genetic defect
Affect males
Rarely affects females

  • Gene for MD codes for dystrophin, a structural cell protein forming a network beneath the plasma membrane that interacts with other cytoskeletal and contractile proteins
  • Without dystrophin, the cells can not retain their proper form or adopt to stress and tend to disintegrate
  • Consequences most prominent in skeletal muscles
47
Q

Duchenne-type dystrophy

A

Most affected born to asymptomatic parents
Mother is usually carrier
Severe muscle wasting begins in utero
Symptoms become evident in early infancy
Children generally in wheelchair with marked deformities
Many die in late teens

48
Q

Becker’s Dystrophy

A

Less incapacitating

Life expectancy into 40’s-50’s

49
Q

Fragile X syndrome

A

Form of mental retardation linked to increased fragility of long arm of chromosome X
Most common form of hereditary mental deficiency in males

50
Q

Multifactorial inheritance

A

Familial diseases not inherited according to rules of Mendelian genetics
Such diseases are products of several genes that interact with each other and are also influenced by exogenous factors
E.g.diabetes, hypertension

51
Q

Anencephaly

A

Example of multifactorial developmental defect

  • Occurs due to incomplete fusion of midline structures covering brain: meninges, bones of calvarium, overlying skin
  • Development of brain and spinal cord severely disturbed
  • Child is born severely malformed with no brain or partial brain
  • Outcome of altered activity of many genes results in spectrum of disorders, ranging from major defects to minor defects of vertebral bones (spina bifida occulta)
  • Predilection of gene malfunction is heritable
  • Folic acid may reduce risk
52
Q

Diabetes Mellitus

A

Multifactorial inheritance

  • Disturbance of intermediate metabolism resulting in hyperglycemia
  • Occurs more often in some families
  • Adult-onset disease called type II or noninsulin-dependent diabetes mellitus (NIDDM)
  • Multifactorial disease with genetic component; development of disease depends on diet, obesity, sedentary lifestyle
53
Q

Prenatal diagnosis

A

Important element of genetic counseling
Can be diagnosed while fetus is in early stages

Ultrasonographic examination

  • Safe and effective (?)
  • Can detect malformations of head, extremities, internal organs, placenta

Chorionic villus biopsy

  • Placental biopsy
  • Provide fetal cells for chromosomal analysis or for biochemical testing

Amniotic fluid analysis
-Fluid aspirated from amniotic sac during 12-18th week, chemical or genetic analysis

Maternal blood analysis

  • high levels of AFP (Alpha Fetal protein) common in certain fetal abnormalities
  • triple-screen marker test - measures maternal AFP, human chorionic gonadotropin and unconjugated estriol; can detect Down’s in 65% of cases
54
Q

Prematurity

A

Normal pregnancy lasts 40 weeks
Fetus attains viability and average weight of 3,500 g (7 lbs 12 oz)
Prematurity - children born before 37th week and less than 2500 g
Immaturity-less than 1500g cannot survive outside neonatal intensive care units

55
Q

Spontaneous abortion or miscarriage

A

approximately 5-10% of pregnancies terminate prematurely due to
Maternal factors
Fetal factors
Placental factors

56
Q

Spontaneous abortion or miscarriage risk factors

A
  • Most important risk factor is premature rupture of amniotic membranes
  • Can occur due to infection or trauma or can be idiopathic
  • Maternal factors include poor nutrition, smoking, substance abuse
  • Infection in mother or fetus
  • genetic defects
57
Q

Neonatal Respiratory Distress Syndrome (NRDS)

A
  • Maturation of fetal lungs occurs rapidly during last 3 months of pregnancy
  • During this time, lungs expand and principle components of alveoli are formed
  • Alveolar cells begin secreting surfactant
  • keeps alveoli open
  • If fetus born prematurely, functionally immature lungs cannot sustiain normal respiration
  • Alveoli collapse
  • Oxygen cannot diffuse into circulation
  • cells damaged and die
  • Necrotic cells and proteins coagulate and form hyaline membranes
  • Gas exchange impeded
  • Infant can die of anoxia within 48 hours
  • Anoxia most prominently affects brain
58
Q

Birth injury

A
  • Various lesions caused by mechanical trauma during delivery
  • Occur most often during the delivery of very large fetuses or abnormally positioned fetuses
  • most common are injuries in head and extremities
59
Q

Sudden Infant death syndrome (SIDS)

A
  • Sudden unexpected death in infants between the ages of 2-9 months
  • Also known as “crib death”
  • Seemingly healthy infants
  • Occurs during sleep
  • No obvious cause of death on autopsy
  • Most common cause of deaths in infants beyond neonatal period
  • occurs in 1/500 births
  • most common in young mothers, women of low socioeconomic status and education, smokers, substance abusers
  • Genetic component
  • premature infants at risk
  • Pathogenesis unknown
  • Back to sleep campaign has drastically reduced incidence

General Pathology (12 decks)

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