3A revision Flashcards
Name 5 conditions that are tested for in Newborn Screening (Guthrie, heel-prick test)?
Cystic Fibrosis – tests immunoreactive trypsinogen (IRT)
Sickle Cell Disease
Congenital hypothyroidism – prevent cretinism – tests TSH
Phenylketonuria – tests phenylalanine
Medium-chain-acyl Coenzyme A (MCCAD) deficiency
Maple Syrup Urine Diseae
Galactosaemia
Homocystinuria
What Causes Phenylketonuria? Name 5 Features?
Autosomal recessive – mutation of the PAH gene (Phenylalanine hydroxylase) on chromosome 12 – ↓PAH enzyme
Amino acid phenylalanine cannot be converted to tyrosine
Accumulation of phenylalanine – converted to phenylketones
Phenylalanine (crosses the blood brain barrier) → intellectual disability
Tyrosine – important in production of neurotransmitters (norepinephrine, epinephrine, Dopamine) – in the adrenal medulla
Learning difficulties
Musty urine
Microcephaly
seizures
What is Kernicterus? Name 5 Signs?
Deposition of Unconjugated bilirubin in the basal ganglia
Irritability Poor feeding Opisthotonas (back arching tetanic convulsions) Seizures coma
Choreoathetoid Cerebral Palsy
Sensineural deafness
Learning difficulties
Name 5 characteristic features of Downs Syndrome?
Trisomy 21
Flat occiput Third fontanelle Wide, flat nasal bridge Epicanthic folds Up-slanting mongoliod eyes (palpebral fissures) Brushfield spots in iris Low-set small ears Small mouth – protruding tongue Single palmar crease (simian) Wide Sandle gap Incurved little finger – clinodactyly Hypotonia
Name 5 associations of Downs Syndrome?
Moderate to severe Learning Disabilities Congenital heart disease – atrioventricular septal defect Duodenal atresia Hirschprung’s disease Hypothyroidism Coeliac disease Hearing impairment from secretory otitis media Obstructive Sleep Apnoea Visual impairment from cataracts, squints, myopia (short-sightedness) Delayed motor milestones Short stature ↑ susceptibility to infection ↑ risk of leukaemia and testicular tumours ↑ risk of atlanto-axial instability Epilepsy Alzheimer’s Disease Infertility
Name 3 modes of inheritance of Downs Syndrome?
Meiotic Non-disjunction
Robertsonian Translocation
Mosaicism
Translocation – the extra 21 chromosome is joined onto another chromosome (normally chromosome 14)
Mosaicism – some cells are normal, some have trisomy 21 - milder phenotype. Normal zygote, with later mitotic non-disjunction
What is Edwards Syndrome? Name 5 features?
Trisomy 18 - ♀ > ♂ Prognosis: most die in utero, 50% die in 1 week. Low birth weight Prominent occiput Small head (microcephaly) Low-set malformed ears Narrow eye-lid fold, palpebral fissure Ocular hypertelorism – wide-spaced eyes, and Ptosis Clenched fist and overlapping fingers Rocker-bottom feet (club feet) Short sternum Small jaw (micrognathia) Cardiac malformations – ventricular septal defect, atrial septal defect, patent ductus arteriosus Kidney malformations
What is Patau Syndrome? Name 5 features?
Trisomy 13
Prognosis: most die within first year of life
Holoprosencephaly – failure of the forebrain to divide properly
Small head (microcephaly)
Small eyes (microphthalmia)
Cataracts, retinal dysplasia / detachment
Polydactyly
Proboscis – blind-ending tube on mid-face
Cleft lip / palate
Kidney defects
Heart defects – ventricular septal defect, patent ductus arteriosus)
Intellectual disability
What is Turner’s Syndrome? Name 5 features?
45 XO ♀ (missing / partial X chromosome)
Short stature Webbed neck (due to cystic hygroma) Lymphoedema of hands and feet in neonate Wide-carrying angle (cubitus valgus) Widely spaced nipples, shield chest Spoon shaped nails Low set ears Low posterior hair-line Short metacarpal IV Pigmented moles Normal Intellect Non-verbal learning disabilities (maths, spatial orientation) Primary Amenorrhoea (due to ovarian dysgenesis) – infertility Delayed puberty Congenital heart defects:- coarctation of the aorta- aortic stenosis- bicuspid aortic valve Renal anomolies (horse-shoe kidney) Hypothyroidism Diabetes ADHD Recurrent Otitis Media / hearing loss Visual impairments
Name 3 Signs of Turner’s Syndrome at Antenatal Fetal ultrasound Scans?
Fetal oedema of the neck, hands and feet
Cystic hygroma
Structural defects of the heart, kidneys
Cystic hygroma is a form of benign lymphangioma – most common in the posterior triangle of the neck
What is Klinefelter Syndrome? Name 5 features?
47 XXY
Hypogonadism - ↓testosterone - ↑FSH Micro-ochidism (small firm testes) Infertility Gynecomastia Weaker muscles Tall stature Poor coordination Less body hair Normal intelligence Behavioural problems, delayed speech, Reading difficulties
Most common cause of male hypogonadism
Diagnosed with delayed puberty
Name 2 most common genetic causes of Learning Difficulties?
Downs syndrome
Fragile X Syndrome
What is Fragile X Syndrome? Name 5 features?
X-linked Recessive – more common in ♂
Caused by >200 trinucleotide (CGG) repeats in the FMR1 gene on the X chromosome
FMR1 – fragile X Mental retardation= gene
Female carriers have mild-moderate learning disabilities
Moderate-severe learning difficulties Macrocephaly Macro-orchidism (large testicles) Long faces Large everted ears Prominent mandible Broad forehead Mitral valve prolapse Joint laxity Scoliosis Autism Hyperactivity
Name 3 genetic conditions caused by Trinucleotide Repeat Expansion Mutations?
Fragile X syndrome Myotonic Dystrophy Huntington’s Disease Spinocerebellar ataxia Friedreich’s ataxia
These genetic disorders become more severe as the triplet expands
How is Duchenne’s Muscular Dystrophy inherited?
X-linked recessive ♂
Most common muscular dystrophy
Mutation (non-sense or frame-shift) in the gene coding for dystrophin on short arm of X chromosome
No dystrophin protein (normally attaches actin to the extracellular matrix to stabilise the sarcolemma (muscle cell membrane)
Influx of Ca2+ ions – causes myofibre necrosis
→ progressive muscle atrophy
Muscle weakness
Age onset – 5 years, life expectancy = 20’s
Name 5 Signs and Symptoms of Duchenne’s Muscular Dystrophy?
Waddling Gait
Gower’s sign – use their arms to ‘walk’ up their body from sitting / lying position – due to lack of hip / thigh muscle strength
Calf pseudohypertrophy – replacement of muscle by fat / fibrous tissue
Slow and Clumsy
Learning disabilities
Cardiomyopathy
Respiratory failure – due to loss of function of diaphragm and intercostal muscles – leads to death
Scoliosis
What blood test would you perform in Duchenne’s Muscular Dystrophy?
↑ creatinine kinase
What is Becker’s Muscular Dystrophy?
Milder form of Duchenne’s Muscular Dystrophy
Missense mutation of the dystrophin gene on the X-chromosome
Some Dystrophin proteins are made
Later age of onset (11 years)
↑ life expectancy
What is Congenital Adrenal Hyperplasia (CAH)?
Autosomal recessive
Defect in the gene for 21-hydroxylase enzyme – needed to make mineralocorticoids and glucocorticoids from the precursor 17-hydroxyprogesterone.
↓mineralocorticoid and glucocorticoid
no negative feedback to the anterior pituitary - ↑ACTH
increases secretion of androgens ↑
Name 5 feature of Congenital Adrenal Hyperplasia (CAH)?
Due to ↓mineralocorticoids (aldosterone):
Salt-losing crisis - Vomiting, dehydration, weight loss, floppiness, collapse
Due to ↓glucocorticoids (cortisol):
Hypoglycaemia
Due to ↑androgens
Virilisation of the external genitalia in female infants – clitoral hypertrophy, fusion of labia
In male patients, penis can be enlarged, pigmented scrotum
Precocious puberty
Non-salt losers – tall stature, muscular build, pubic hair, acne
Name 3 Laboratory findings of Congenital Adrenal Hyperplasia (CAH)?
Hypoglycaemia – (↓ glucose) – due to ↓cortisol
Hyponatraemia – (↓ sodium) – due to ↓aldosterone
Hyperkalaemia – (↑ potassium) – due to ↓aldosterone
Metabolic acidosis
↑ urea (dehydration)
↑17α-hydroxyprogesterone
↑ACTH (adrenocorticotropic hormone) – loss of negative feedback of cortisol
→ androgens ↑
What is the treatment of Congenital Adrenal Hyperplasia (CAH)?
Hydrocortisone
Fludrocortisone
Lifelong
Describe the Parts and Functions of the Adrenal Gland?
Adrenal Cortex: GFR
Zona Glomerulosa – mineralocorticoids, e.g. Aldosterone
Zona Fasciculata – glucocorticoids, e.g. cortisol
Zona Reticularis – androgens, e.g. dehydroepiandrosterone (DHEA)
Adrenal Medulla – chromaffin cells – convert tyrosine to catecholamine’s, e.g. epinephrine, norepinephrine
What is the risk with treating hyponatraemia quickly?
↑risk of cerebral pontine myelinolysis (CPM)
Damage to the myelin sheath of nerves in the brainstem (pons)
Paralysis, dysphagia, dysarthria
↑ sodium too quickly - drives water out of brain cells
Treatment of Salt-losing crisis in CAH: IV dextrose and IV hydrocortisone