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6 month old infant presents severe mental retardation and hypopigmentation. In your investigations you find that there are high levels of serum phenylalanine.
What disease do you suspect?
What enzyme is defective?
What is the associated inheritance pattern?
→ phenylalanine hydroxylase
6 month old infant presents severe mental retardation and a mousy urine smell. What is the disease? What makes the smell mousy?
→ accumulation of phenylacetic acid
What is the tx for pts diagnosed with PKU?
Phenylalanine restriction in the diet starting from postnatal period
Expectant mothers homozygous for PKU: low-phenylalanine diet
What is the enzyme deficient in galactosemia?
As a result, what accumulates?
galactose-1-phosphate uridyl transferase (GALT, 9p)
Infant presents with failure to thrive with vomiting and diarrhea following milk ingestion. He also appears jaundice with hepatomegaly. Within a few weeks he develops cataracts.
What is your likely dx?
How does a mutated CFTR channel lead to pancreatic duct plugging?
→ ↓ HCO₃⁻ secretions
→ acidic pancreatic duct secretions
→ mucin precipitation
What respiratory tract disorders are CF pts at risk for?
chronic bronchitis, bronchiolitis, bronchiectasis, lung abscesses, sinusitis and sinonasal polyps
Why is there male infertility in CF pts even though spermatogenesis is not affected?
bilateral absence of vas deferens
What are common multifactorial diseases in adults?
hypertension, atherosclerosis, DM2, allergic diathesis, psoriasis
What are common multifactorial diseases in children?
pyloric stenosis, cleft lip and palate, congenital heart disease, hypospadias, hirschprung disease
What is the Lyon effect?
random and irreversible inactivation of 2nd X chromosome in females during embryogenesis
Why do affected X-link recessive disorder affected men never pass on their disorder to their sons?
They pass their Y to their sons.
All their daughters will be carriers though.
What syndrome is associated with the pseudoautosomal genes on the inactivated X chromosome?
What is the gene?
FMR1 @ Xq27 → CGG repeat expansion
How does increased CGG repeats in FMR1 lead to mental retardation?
↑ repeats → ↑ gene methylation → altered synaptic activity → mental retardation and physical abnormalities
How can the physical manifestations of fragile-X syndrome present?
Fragile-X shows worsening features in each successive generation. What is the phenomenon called?
What are the genetic mechanims that can lead to Prader-Willi and Angelman syndromes?
Pt presents with mental retardation, hyperphagia, obesity, and hypogonadism. What do you suspect?
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