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MTM Exam 3 > Cell Biology - W1 Pathology > Flashcards

Cell Biology - W1 Pathology Flashcards

1
Q

Explain the mechanism of Acanthocytosis or Spur Cell Anemia.

A

In this disease, abnormal lipoproteins create high cholesterol content (& high plasma cholesterol levels). Abnormally high cholesterol levels present a chronic-like liver disease, similar to liver cirrhosis. These RBC’s have high cholesterol content in their plasma membranes, which results in finger-like membrane projections rather than a smooth surface.

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2
Q

What glycolipid receptor, that is found on the surface of intestinal epithelial cells, is targeted by the cholera toxin?

A

GM1 Ganglioside

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3
Q

What disease is associated with a RBC cytoskeletal membrane defect?

A

Hereditary Spherocytosis

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4
Q

What is the pattern of inheritance for Hereditary Spherocytosis?

A

Autosomal Dominant

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5
Q

What is the membrane defect in Spherocytosis?

A

Spectrin, Ankyrin, or Protein 4.1 deficiency

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6
Q

What are some common clinical presentations of Hereditary Spherocytosis?

A
  • Splenomegaly
  • Jaundice (Haptoglobin)
  • Gall Stones (Hyperbilirubinemia)
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7
Q

RBC’s that are opaque, spheroidal, rigid, and have no area of central pallor.

A

Spherocytes

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8
Q

RBC’s that are irregular, blunt, and have 5-10 finger like projections on the outer membrane.

A

Acanthocytes

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9
Q

What is the pattern of inheritance for Spinal Muscular Atrophy?

A

Autosomal Recessive

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10
Q

What are some common clinical presentations for spinal muscular atrophy?

A
  • Muscle weakness and atrophy
  • Hypotonia
  • Dysphagia and feeding difficulties
  • Respiratory problems
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11
Q

Explain the mechanism for Spinal Muscular Atrophy.

A

This disease is due to a “Gem” malformation. Gem contains the SMN (Survival Motor Neuron) protein. The mutation in Gem > mutation in SMN > causes defective snRNP assembly > leads to defective pre-mRNA splicing > loss of motor neurons in spinal cord & brainstem.

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12
Q

What are some common clinical presentations for Emery-Dreifuss Muscular Dystrophy (skeletal & cardiac myopathy)?

A
  • Contractures (elbows, ankles, and neck)
  • Muscle weakness & atrophy
  • Microscopy shows fragile nuclei
  • Sudden heart failure (most common)
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13
Q

Explain the mechanism for Emery-Dreifuss Muscular Dystrophy (EDMD)?

A

In this disease, there is a mutation in either Emerin or Lamin A/C. Due to this mutation, the nuclear envelope is disrupted and the chromatin of the nucleus is extruded into the cytoplasm.

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14
Q

Explain the mechanism for Dilated Cardiomyopathy.

A

Fragile nuclear lamina (usually due to a lamin A/C defect) > nuclear structures/content damaged > cell death > Congestive Heart Failure (most common)

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15
Q

What are some common clinical presentations for lipodystrophy?

A
  • Excess adipose tissue in face and neck

- Peripheral lipoatrophy w/ muscle prominence

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16
Q

Explain the mechanism for lipodystrophy.

A

In this disease, the individual has a defect with the lamin A/C. PreLamin A interacts with an adipocyte transcription factor, so there is an impaired adipocyte differentiation.

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17
Q

What is the pattern of inheritance for Hutchinson-Gilford Progeria Syndrome?

A

Sporadic Autosomal Dominant

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18
Q

What are some common clinical features of Hutchinson-Gilford Progeria?

A
  • 18 to 24 months: failure to thrive
  • Alopecia
  • Accelerated aging
  • 13 year life expectancy
  • Arteriosclerosis
  • Death by MI or CHF (80%)
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19
Q

Explain the mechanism for Hutchinson-Gilford Progeria.

A

In this disease, the patient has an altered lamin A > unstable nuclear envelope > progressive nuclear damage > premature cell death.

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20
Q

What are the different types of lysosomal lipid storage diseases?

A
  • Sphingolipidoses: accumulation of sphingolipids
  • Mucolipidoses: accumulation of glycoprotein & glycolipids
  • Leukodystrophies
  • Mucopolysaccharidoses: accumulation of sulfated GAGs
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21
Q

List the sphingolipidoses diseases.

A
  • Gaucher’s disease
  • Niemann - Pick disease
  • Tay Sachs Disease
  • Metachromatic Leukodystrophy
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22
Q

List the mucolipidoses diseases.

A

I: Sialidosis
II: I-Cell Disease
III: Pseudo-Hurler Polydystrophy

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23
Q

List the mucopolysaccharidoses diseases.

A
  • Hurler Syndrome
  • Hunter Syndrome
  • Sanfilippo Syndrome
  • Morquio Syndrome
  • Maroteux-Lamy Syndrome
  • Sly Syndrome
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24
Q

Explain the mechanism for I-Cell Disease (Mucolipidosis II).

A

In this disease, the patient has a deficiency in the “Golgi N-acetylglucosamine phosphotransferase”, which prevents the formation of the M6P tag. As a result, the acid hydrolases lacking M6P are secreted extracellularly.

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25
Q

What are some common clinical presentations for I-Cell Disease (Mucolipidosis II)?

A
  • Coarse features
  • Corneal Clouding
  • Restricted joint movement/psychomotor retardation
  • Enlarged liver, spleen, and heart valves
  • Death by CHF or RTI
  • Life expectancy <10 yrs
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26
Q

What is the pattern of inheritance for Mucopolysaccharide diseases?

A

They are all autosomal recessive except for Hunter (which is X-linked).

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27
Q

What is the mechanism for a Mucopolysaccharide disease?

A

Defective degradation of GAG (glycosaminoglycans) or sulfated polysaccharides.

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28
Q

What are some common clinical presentations for Mucopolysaccharide diseases?

A
  • Coarse facial features
  • Corneal clouding
  • Joint stiffness; skeletal deformities
  • Hepatosplenomegaly
  • Mental retardation
  • Hirsutism
  • Arterial deposits
  • Urinary excretion of the GAG often high
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29
Q

How is Pseudo-Hurler Polydystrophy (Mucolipidosis III) similar to I-Cell?

A
  • Milder form of the disease

- Later onset and survival into adulthood

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30
Q

Explain the mechanism of Hurler Syndrome.

A

In this disease, the patient has a deficiency in alpha - L - iduronidase. This leads to the build-up of dermatan sulfate and heparan sulfate.

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31
Q

What are some common clinical presentations of Hurler Syndrome?

A
  • Presents at a few months old (normal at birth)
  • Physical and mental deterioration
  • Growth stops at 2-4 yrs
  • Hepatosplenomegaly
  • Deafness
  • Skeletal deformity
  • Coarse facial features
  • Hirsutism
  • Thickened skin
  • Corneal Clouding**
  • Death < 10 yrs
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32
Q

Explain the mechanism for Scheie & Hurler-Scheie Syndrome.

A

In this disease, there is only RESIDUAL alpha -L - iduronidase activity. This is a milder version of Hurler Syndrome and one of the mildest types of MPS I.

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33
Q

Explain the mechanism for Hunter Syndrome (Mucopolysaccharidoses II).

A

In this disease, there is a deficiency of iduronodate sulphatase. This leads to an accumulation of dermatan sulphate and heparan sulfate.

34
Q

What clinical presentations in Hunter Syndrome are different from Hurler Syndrome?

A
  • Later presentation (2-4 yrs)
  • Milder course (survives until 30)
  • No corneal clouding
35
Q

What is the mechanism of Tay-Sachs disease?

A

Accumulation of gangliosides (GM2), which is a sphingolipid. This is normally broken down by beta-hexosaminidase A.

36
Q

What are some common clinical presentations for Tay-Sachs Disease?

A
  • Rapid and progressive neurodegeneration
  • Blindness
  • Cherry red macula
  • Muscular weakness
  • Seizures
37
Q

What is the mechanism of metachromatic leukodystrophy?

A

Accumulation of sulfates, which is normally broken down by arylsulfatase A.

38
Q

What are some common clinical presentations of metachromatic leukodystrophy?

A
  • Cognitive deterioration
  • Demyelination
  • Progressive paralysis
  • Dementia in adult form
  • Nerves stain yellow-brown with cresyl violet (metachromasia)
39
Q

What is the pattern of inheritance for metachromatic leukodystrophy?

A

Autosomal Recessive

40
Q

What is the pattern of inheritance for Chédiak-Higashi Syndrome?

A

Autosomal Recessive

41
Q

Explain the mechanism of Chédiak-Higashi Syndrome.

A

In this disease, the patient has a mutation in the CHS1/LYST gene. This gene normally encodes for a lysosomal trafficking regulatory protein that induces vesicle fusion.

The result of this mutation leads to delayed phagosome to lysosome fusion in leukocytes, autophagocytosis of melanosomes in melanocytes, and granular defects in natural killer cells & platelets.

42
Q

What are some common clinical presentations of Chédiak-Higashi Syndrome?

A
  • Albinism/Hypopigmentation
  • Recurrent infections (life-threatening)
  • Mild coagulation defects
  • Varying neurological problems
43
Q

What is the pattern of inheritance for cystic fibrosis?

A

Autosomal Recessive

44
Q

Explain the mechanism of Cystic Fibrosis.

A

In this disease, there is a mutation in the CFTR gene which is crucial for Cl- ion channeling (a plasma transmembrane protein). The mutation leads to an incorrectly folded protein that never gets transported to the plasma membrane due to chaperone regulation.

45
Q

Cystic Fibrosis is accompanied by what lung alteration? What are some common clinical presentations for this complication?

A

It usually has a secondary complication called Bronchiectasis.

  • Chronic cough and dyspnea
  • Irreversible bronchial dilation and thickened bronchial walls
  • Dilated central bronchi
  • Hyperexpansion
  • Mucoid impaction > obstruction and 2 year infection > fibrosis > bronchiectasis
  • Most common cause of death: respiratory failure
46
Q

Explain the mechanism for Familial Hypercholesterolemia, Class II.

A

In this disease, there is a mutation in the LDL-R (receptor). This prevents the LDL from entering the RER, where it can be regulated (depending on how great or low the concentrations are).

47
Q

What is the pattern of inheritance for familial hypercholesterolemia?

A

Autosomal Dominant, with Semi-Dominance (homozygotes die at a very young age).

48
Q

What are some common clinical presentations of familial hypercholesterolemia?

A
  • Xanthomata (fatty deposits on the skin)
  • Xanthelasmata (fatty deposits on eyelids)
  • Corneal arcus (arc on the top/bottom of iris)
  • Major risk factor for CHD (premature atherosclerosis)
49
Q

Explain the mechanism for I-Cell Disease (Mucolipidosis II).

A

In this disease, the patient has a deficiency of N-acetylglucosamine phosphotransferase. This chemical is responsible for producing M6P, which tags lysosomes in the cis-Golgi. Without M6P, the acid hydrolases are secreted intracellularly and waste products accumulate to form inclusion bodies.

50
Q

What are some clinical presentations for I-Cell Disease (Mucolipidosis II)?

A
  • Coarse facial features
  • Skeletal abnormalities
  • Restricted joint movement
  • Psychomotor retardation
  • Enlarged liver, spleen, and heart valves
  • Death by CHF/RTI (<10 yrs)
51
Q

Explain the mechanism of clostridium botulinum.

A

Botulinum toxins are neurotoxins that cleave synaptobrevin (v-SNARE) from the motor neurons. This prevents the vesicles carrying ACh from fusing and releasing neurotransmitters at the neuromuscular junction.

52
Q

Explain the mechanism for tetanus toxin (tetanospasmin).

A

The toxin travels retrograde, into the spinal cord, and then into cell bodies of inhibitory neurons. Tetanus cleaves synaptobrevin (v-SNARE), which prevents the vesicle fusion and release of GABA & glycine (inhibitory NT’s) onto the motor neuron at the neuromuscular junction.

53
Q

Explain the mechanism of Familial Hypercholesterolemia, Class IV.

A

In this disease, the LDL- R do not cluster on the cell surface, which causes ineffective endocytosis.

54
Q

What is the pattern of inheritance for Barth Syndrome?

A

X-Linked Disorder

55
Q

Explain the mechanism for Barth Syndrome.

A

In this disease, there is a mutation in cardiolipin synthesis. Without cardiolipin, the inner membrane of the mitochondria does not function correctly. This leads to unfunctional and distorted mitochondria.

56
Q

How is gout produced in the body and what do we do to treat it?

A

Gout is produced by xanthine oxidase (purines are converted into xanthine, then into urate for excretion). In order to treat it, we must inhibit xanthine oxidase, which is done with “allopurinol”.

57
Q

What is the pattern of inheritance of Zellweger syndrome?

A

Autosomal Recessive

58
Q

Explain the mechanism of Zellweger Syndrome.

A

In this disease, the membrane does not recognize the AA signal used to import peroxisomal proteins. The failure to import these enzymes leads to a deficiency > VLCFA accumulate in blood & tissues > lack of plasmalogen.

59
Q

In Zellweger syndrome, where do the VLCFAs accumulate? What kind of clinical complications does this cause?

A

Primarily in the glial cell membranes (no beta oxidation) and in the liver.

  • Abnormal brain development
  • Hypomyelination (due to lack of plasmalogen)
  • Liver failure and hepatomegaly
  • Lack of bile acids (decreased fat absorption> loss of energy > weak muscles)
60
Q

What is the most common peroxisomal disorder?

A

X-Linked Adrenoleukodystrophy (XALD)

61
Q

Explain the mechanism for XALD.

A

In this disease, there is a defect in the transport (defective membrane protein) of VLCFA into the peroxisomes. This leads to a defective breakdown of VLCFAs.

62
Q

Where do the VLCFAs accumulate in XALD?

A

Primarily in the glial cell membranes (leuko = white matter of brain) and adrenal cortex.

63
Q

Zellweger spectrums are diseases with PEX mutations. Here the defective peroxisomal proteins biogenesis leads to failure of importing peroxisomal proteins > empty peroxisomes. What are these diseases?

A
  • Zellweger Syndrome
  • Neonatal Adrenoleukodystrophy (NALD)
  • Infantile Refsum Disease
  • Hyperpipecolactemia
64
Q

What are some common clinical presentations of Barth Syndrome?

A
  • Cardiomyopathy
  • Neutropenia
  • High infant mortality
  • Muscle weakness and fatigue
65
Q

What is the pattern of inheritance for Progressive External Ophtalmoplegia (PEO)?

A

Autosomal Dominant, but it can also be inherited via Mitochondria.

66
Q

Explain the mechanism of PEO.

A

In this disease, there is both nuclear and mitochondrial errors. Mutations are in POLG and TWINK encoding (which help with repair). This leads to large mtDNA depletions or large deletions in the mtDNA.

67
Q

What are some common clinical presentations for PEO?

A
  • Late age of onset (18-40 yrs)
  • Ragged red muscle fibers
  • BILATERAL ptosis
  • Exercise intolerance (muscle weakness)
68
Q

Mutations in DNA Polymerase Gamma leads to what diseases and/or syndromes?

A
  • PEO (Progressive External Ophtalmoplegia)
  • Alpers Syndrome
  • Ataxia Neuropathy
  • Male Infertility
69
Q

What are the three major types of disease causing mutations in the mtDNA?

A
  1. Deletions or Duplications
  2. Point Mutations in the tRNA
  3. Missense mutations in the coding regions
70
Q

What three diseases are associated with giant deletions in the mtDNA?

A
  1. PEO
  2. Kearns-Sayre Syndrome
  3. Pearson Syndrome
71
Q

What are some common clinical features of Kearns-Sayre Syndrome?

A
  • No bone marrow involvement
  • Late Onset
  • Contain >80% mutated mtDNA (ragged red fibers)
  • Longer lifespan than Pearson syndrome
72
Q

What are some common clinical features of Pearson Syndrome?

A
  • Bone marrow involvement
  • Pediatric disease
  • More severe than KSS
  • Pancytopenia (deficient in red, white, and platelet cells) and sideroblastic anmeia
73
Q

What diseases are associated with mutations in the mitochondrial tRNA genes?

A
  1. MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke Like Episodes)
  2. MERF (Myoclonus Epilepsy and Ragged Red Fibers)
74
Q

What diseases are associated with mutations in the mitochondrial protein coding genes?

A
  1. LHON (Leber’s Hereditary Optic Neuropathy)
  2. NARP (Neurogenic muscle weakness, Ataxia, and Retinitis Pigmentosa)
  3. MILS (Maternally-Inherited Leigh Syndrome)
75
Q

What is the mode of inheritance for diseases with giant deletions in mtDNA?

A

Heteroplasmic

76
Q

What is the pattern of inheritance for the two mitochondrial tRNA diseases?

A

Heteroplasmic

77
Q

Explain the mechanism for MELAS.

A

Mutated tRNA Leucine gene.

78
Q

Explain the mechanism for MERF.

A

Mutated tRNA Lysine gene.

79
Q

Explain the mechanism of LHON and it’s patten of inheritance.

A

The subunits of Complex I (NADH Dehydrogenase) are mutated. This is the ONLY disease that may be homoplasmic.

80
Q

Explain the mechanism of NARP and it’s pattern of inheritance.

A

A mutation in ATPase 6 gene of Complex V (ATP Synthase).

Heteroplasmic inheritance.

81
Q

This disease has more than 75 mutations of different genes in both the nucleus and mitochondria. Children from this disease usually die by the age of 3.

A

Leigh Syndrome

82
Q

What disease is a subtype of Leigh Syndrome but has the same mechanism of disease as NARP (more severe with a larger portion of mutated mtDNA)?

A

MILS (Maternally- Inherited Leigh Syndrome).

MTM Exam 3 (6 decks)

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