Clinical Diagnosis Flashcards
Trisomy 21 Features (Signs and Symptoms)
Down Syndrome:
-Intellectual Disability
-Short Stature
-Depressed nasal bridge, upslanting palpebral fissures, epicanthal folds
-Congenital heart defects
-Single palmar crease
-Develop changes similar to Alzheimer disease at a relatively young age
Genetic Causes of Down Syndrome
Non-disjunction during meiosis
*May also result from Robertsonian translocation
Trisomy 18 Features
Edwards Syndrome
-Clenched fist, overlapping of fingers
-Rocker bottom feet
-Congenital heart defects
-Low-set ears, small lower jaw (micrognathia)
-Microcephaly
-Intellectual disability
Genetic mechanism of Trisomy 18
Nondisjunction during oogenesis
Trisomy 13 Features
Patau syndrome
-Polydactyly
-Cleft lip and palate
-Microphthalmia
-Microcephaly
-Intellectual disability
-Cardiac anomalies (VSD or ASD)
Genetic mechanism of Patau syndrome
-Nondisjunction during oogenesis
Names of Sex chromosome Aneuploidy
-Turner Syndrome (45, X)
-Klinefelter Syndrome (47, XXY)
Genetic basis of 45, X
Turner Syndrome: X chromosome monosomy
-Usually due to nondisjunction during spermatogenesis
Features of Turner Syndrome
-Short stature
-Webbed neck, cystic hygroma birth (neck swelling)
-Primary amenorrhea
-Gonadal dysgenesis
-“Streak ovaries”
-Lymphoedema of hands and feet
-Many are mosaic: many have no Barr body (Inactivated X-chromosome)
Genetic mechanism of 47, XXY and name
Klinefelter syndrome
-Nondisjunction during meiosis
-Some individuals may be mosaic
Features of Klinefelter syndrome
-Gynecomastia
-Female distribution of hair
-Infertility and testicular atrophy due to low levels of testosterone
-Feminization of features
Trisomy Rescue
One way that a person could be mosaic for Down Syndrome:
1) Non-disjunction may occur in the ovum during oogenesis, and fertilization by a normal sperm leads to trisomy 21 in the conception
2) During a post-fertilization mitosis, one of the extra chromosome 21 is evicted during cell division
Reciprocal Translocation
Exchange of genetic material between non-homologous chromosomes
What are the effects of reciprocal translocation in carriers?
Somatic cells: 1) silent
2) Transformation to cancer and increased growth rate of cells
Cri-du-chat Syndrome
Deletion of chromosome 5p
-High pitched, cat-like cry
-Micrognathia which influences the cat-like cry and later, speech problems
-Severe intellectual disability
-Microcephaly
-Hypertelorism (widely spaced eyes)
22q11.2 Deletion Syndrome
Velocardiofacial syndrome or DiGeorge Syndrome
-CATCH 22 :
-Congenital heart defects
-Absence of thymus (thymic aplasia): might cause immunological problems
-Cleft lip & palate, maybe speech difficulty
-Hypocalcemia
-Learning disability
-Facial anomalies
-Increased risk for schizophrenia
Wolf-Hirschhorn syndrome (WHS)
-Deletion of ch 4p
-Seizures
-Skeletal abnormalities and congenital heart defects
-Spectrum of intellectual and developmental delay, mild to severe
-Facial anomalies, widely spaced eyes, high-arched eyebrows, broad and flat nasal bridge often described as similar to a roman helmet, short philtrum, downturned mouth, small chin
Beckwith-Wiedemann Syndrome (BWS) Features
-Macroglossia (enlarged tongue)
-Birth weight and length greater than 90 percentile
-Abdominal wall defects such as umbilical hernia
-Ear creases or pits
-Neonatal hypoglycemia
-Increased risk of cancer
Albinism is due to a deficiency of what?
The pigment melanin due to lack of activity of the enzyme tyrosinase
Alkaptonuria is due to:
The buildup of a toxic substance due to an enzyme deficiency:
-black urine disease, is a very rare inherited disorder that prevents the body fully breaking down two protein building blocks (amino acids) called tyrosine and phenylalanine. It results in a build-up of a chemical called homogentisic acid in the body.
Phenylketonuria (PKU) is due to:
Defect of phenylalanine metabolism due to deficiency of the enzyme phenylalanine hydroxylase
-Phenylalanine and its metabolites accumulate to toxic levels
-There is also a deficiency of downstream products of phenylalanine including the neurotransmitter DOPA and the pigment melanin
