Protein Metabolism

Question 1

What clinical features due Urea Cycle defects like (OTC deficiency) present with and how do you treat it?

Answer 1

Hyperammonemia
NO acidosis 
NO ketones
Symptom free until hypotonia
Coma
Respiratory alkalosis and lactic acidosis

Treat: need to reduce NH4 by reducing protein intake and increasing glucose via IV

Question 2

What are the clinical features associated with Maple Syrup Urine Disease?

Answer 2

Maple syrup-smelling urine
Tachypnea
Shallow breathing pattern
Profound lethargy
Irritability
Poor feeding
Hypertonicity
Ketonuria
*Presents in 1st week of life.

Question 3

What branched chain amino acids are elevated in Maple Syrup Urine Disease?

Answer 3

Valine
Iisoleucine
Alloisoleucine (NEVER normal in infants)
Leucine

These levels are elevated by the end of the FIRST DAY of life

Question 4

What are the causes and clinical features associated with Homocystinuria?

Answer 4

Caused:
Error in methionine metabolism. Cystathionine synthase deficiency results in elevated homocystine, methionine, and urine homocystine.

Dislocated Lens
Skeletal abnormalities
Cognitive defects
Unpleasant odor
Light-colored skin and hair
Eyes different than family members
Thromboembolism
Pectus excavatum 

*Differentiate from Marfan’s-lens upward/anterior with NO cognitive defects, Homocystein-lens downward/posterior with possible cognitive defects

Question 5

How do you diagnosis and treat Homocystinuria?

Answer 5

Diagnosis:
Homocysteine in the urine

Treatment:
Diet low in methionine and protein as well as betaine, folate, Vit B12 supplementation

Question 6

What is the cause for Phenlyketonuria (PKU) and what are its clinical features?

Answer 6

Cause:
Defciency of the enzyme that converts phenylalanine to tyrosine

Clinical features:
Asymptomatic for a few months
Blonde Hair
Blue Eyes
Musty/Mousy Odor
Severe vomiting
Irritability
Eczema
Profound intellectual disability

Question 7

How is Phenlyketonuria (PKU) screened for?

Answer 7

It is on the NBS, but not all of them will be positive.

NBS only detects elevated phenylalanine levels so it could also be due to delayed enzyme maturation, hyperphenylalaninemia, or biopterin deficiency

PKU screening is ONLY VALID after a “protein feeding” Must be done 48-72 hours and no the initial NBS.

Question 8

How do you treat Phenlyketonuria (PKU)?

Answer 8

Low phenylalanine formula (Lofenalac)

But be careful of overtreatment: (get low phenylalanine levels)
Lethargy
Rash
Diarrhea

Also make sure you get enough Tyrosine in the diet!