Genetic Disorders Flashcards
Marfan Syndrome
- What is the mutation?
- What is its inheritance pattern?
- What structure does it affect?
- What is its function?
- What are the symptoms?
- FBN1 gene on 15q
- Autosomal dominant (80% genetic)
-
Fibrillin-1 (ECM protein)
- prevents correct microfibril elastic fiber formation
- Component of microfibril elastic fibers
- aorta
- ligaments
- ciliary zonules (holds lens in place)
- Excess TGFß b/c no microfibrils to sequester it
- Symptoms:
- Arachnodactyly (long extremeties and long fingers)
- Deeply depressed sternum
- Ectopia lentis (dislocation of the lens)
- CV disease:
- mitral valve prolapse (most common)
- Dilation of aortic valve ring/root of aorta –> rupture
Ehlers-Danlos Syndromes
- What is its inheritance pattern?
- What structure does it affect?
- What is its function?
- What are the symptoms?
- Autosomal dominant (80%) genetic
- fibrillar collagen (lack of tensile strength)
- part of ECM: holds things together
- Classic form syptoms: (w/Hypermobility variant)
- hyperextensible/stretchable skin
- vulnerable to damage
- Joint hypermobility
- atrophic scars
- Other variants:
- diaphragmatic herniation
- Ocular fragility (retinal detatchment/rupture cornea)
Classical form of Ehlers-Danlos syndrome
- Hyperextensible/stretchable skin
- Vulnerable to damage from minor trauma
- Hypermobile joints (Hypermobility variant)
- Atrophic scars (Hypermobility variant)
Characteristics of Vascular Ehlers-Danlos syndrome
- Type of abnormal collagen
- Symptoms
- Type III collagen
- Symptoms:
- Rupture of uterus, colon, large arteries
Characteristics of Kyphoscoliosis Ehlers-Danlos syndrome
- Inheritance pattern
- Symptoms
- Autosomal recessive
- Symptoms:
- Congenital Scoliosis
- Joint laxity
Characteristics of Arthrochalasia EDS
- Inheritance pattern
- Specific Defect
- Symptoms
- Autosomal dominant
- Problems converting Type I procollagen to collagen
- Symptoms: Joint hypermobility
Characteristics of dermatosparaxis EDS
- Inheritance pattern
- Specific Defect
- Symptoms
- Autosomal dominant
- defective conversion of type I procollagen to collagen
- Symptom: severe skin fragility
Hypermobility variant of EDS
- Associated with what other form?
- Symptoms
- With classical form
- Symptoms:
- joint hypermobility
- joints painful, predisposed to dislocation
- Atrophic scar
Familial Hypercholesterolemia
- What is its inheritance pattern?
- What structure does it affect?
- What is its function?
- What is the difference in expression between heterozygotes and homozygotes? symptoms?
- What is the treatment?
- Autosomal dominant
- Mutation in gene for LDL receptor –>
- Uptake of LDL (low LDL –> overproduction of cholesterol)
- Difference:
- Homozygotes: 5-6x normal Cholesterol levels
- xanthomas
- premature atherosclerosis
- MI before age 20
- Heterozygotes: 2-3x normal lvls
- premature atherosclerosis
- Homozygotes: 5-6x normal Cholesterol levels
- Treatment: Statins
- Inhibit HMG CoA reductase
- (-) cholesterol synthesis
- Inhibit HMG CoA reductase
What are the 5 classes of LDL receptor mutations?
- Type 1
- no receptor synthesis
- Type 2
- Folding defect in LDL receptor
- doesn’t leave ER
- Type 3
- no or poor LDL binding to receptor
- Type 4
- Receptor not in clathrin-coated pit, so bound LDL is not internalized
- Type 5
- LDL not released from receptor,so receptor is not recycled
What is pleotrophism?
a single gene affects a number of phenotypic traits in the same organism.
Tay-Sachs disease
- Symptoms:
- Defect:
- Protein accumulated in cells
- Cytology
- Symptoms:
- rapidly deteriorating motor and mental functioning at about 6 months of age
- Cherry red spot in the macula
- Defect:
- deficiency in hexosaminidase-alpha subunit
- gene on 15q
- Protein:
- GM2 Ganglioside
- Cytology:
- Neurons enlarged
- whorls of membrane layers in lysosomes
Diagnose:
Patient is 6 months old. Presents with rapidly deteriorating motor and mental functioning. Exam finds cherry red spot in the macula.
- What is the disease?
- What is the pathology?
Tay-Sachs disease
- Defect:
- deficiency in hexosaminidase-alpha subunit
- gene on 15q
- Protein:
- GM2 Ganglioside
Neimann-Pick Disease Type A
- Symptoms:
- Defect:
- Protein accumulated in cells
- Cytology
- Symptoms: Severe infantile form
- CNS involvement
- Hepatosplenomegaly
- Defect:
- deficiency in sphingomyelinase
- Protein accumulated in cells
- sphingomyelin
- Cytology
- Foamy cells from accumulation of lipid
Neimann-Pick disease type B
- Symptoms:
- Defect:
- Accumulation in cells
- Cytology
- Symptoms:
- little or no CNS involvement
- Respiratory insufficiency
- Hepatoslenomegaly
- Defect:
- Deficiency in sphingomyelinase
- Protein accumulated in cells
- sphingomyelin
- Cytology
- foamy cells due to accumulation of lipid
Neimann-Pick Type C
- Symptoms:
- Defect:
- Accumulation in cells
- Symptoms:
- Neuronal degeneration (CNS effects)
- Hepatosplenomegaly
- Defect:
- NPC1 gene mutation: impaired regulation of cholesterol
- NPC2 gene mutation: impaired release of free cholesterol from lysosomes
- Protein accumulated in cells:
- cholesterol and glycolipids in lysosomes
Gaucher Disease
- Symptoms:
- Defect:
- Accumulation in cells
- Cytology
- Symptoms:
- varies by type
- Often CNS manifestations (type II and III)
- hepatosplenomegaly (Type I)
- Anemia (Type I)
- Pathological fractures (Type I)
- Defect:
- Deficiency of glucocerebrosidase
- Accumulation in cells
- Glucocerebroside
- Accumulates in phagocytes
- Cytology
- Gaucher cells (phagocyte, accumulation makes them foamy)
Diagnose:
Patient is a few months old. Presents with CNS dysfunction and seizures along with hepatosplenomegaly. Cytology shows foamy macrophages.
- What is the disease? Be specific.
- What is the defect?
- What is the treatment?
Gaucher Disease Type II
- Defect: deficiency of glucocerebrosidase (accumulation)
- Treatment:
- Recombinant glucocerebrosidase
- Bone marrow transplant
(Type III onset in mid-to late childhood)
Diagnose:
Patient presents with hepatosplenomegaly, anemia, bone pain and pathological fractures. Cytology shows foamy macrophages.
What is the disease? Be specific.
What is the defect?
What is the treatment?
Gaucher Disease Type I
- Deficiency of glucocerebrosidase
- Treatment:
- Recombinant glucocerebrosidase
- Bone marrow transplant
Hurler’s syndrome/Mucopolysaccharidosis I
- Symptoms:
- Defect:
- Accumulation in cells
- Cytology
- Symptoms:
- organomegaly
- Growth and mental retardation
- Skeletal deformities
- Corneal clouding (different from MPSII/Hunters)
- Defect:
- deficiency in alpha-L-iduronidase
- Accumulation in cells
- Dermatan sulfate
- Heparan sulfate
- (both are glycosaminoglycans)
- Cytology
- Enlarged, vacuolated nurons