Inborn Errors of Metabolism and Nutrition Flashcards
What criteria should a genetic screening program fulfill?
- Tested disorder is prevalent and serious
- The disorder can be pre-symptomatically impacted through lifestyle changes, screening, meds or other risk-reducing interventions
- Identification of risk does not result in undue discrimination or harm
When should inborn errors of metabolism be suspected?
- Child’s symptoms accompany changes in diet
- Child’s development decreases
- Notable specific food preferences/aversions
- Fam hx of retardation or unexplained deaths in 1st and 2nd degree relatives
- Present w/sepsis like symptoms
- Recurrent hypoglycemia
- Neuro syndromes
- Unexplained acidosis
What is phenylketonuria?
- AA metabolism disorder with decreased conversion of phenylalanine to tyrosine
- Autosomal recessive
Clinical presentation of PKU in infants
- Severe mental retardation (IQ 30)
- Hyperactivity
- Seizures
- Light complexion, blond
- Eczema
What results in the best outcome of PKU in infants?
Elimination diet started in 1st month of life
Treatment of PKU
- Regulation of maternal hyperphenylalaninemia prior to conception and throughout pregnancy to prevent fetal damage
- After birth, phenylalanine deficiency diet to maintain low levels (under 6 mg/dL)
What is galactosemia?
- Autosomal recessive d/o of metabolism
- Inability to metabolize galactose
Clinical presentation of galactosemia
- Vomiting
- Jaundice
- Hepatomegaly
- Rapid onset of liver insufficiency after starting milk feeding
Treatment of galactosemia
- Avoidance of galactose for life (use soy milk)
- Calcium replacement
What is maple syrup urine disease?
- Autosomal recessive d/o of metabolism
- Deficiency of an enzyme that processes certain AAs (leucine, isoleucine, valine)
- Results in ketoaciduria
Clinical presentation of maple syrup urine disease
- Normal at birth
- 1 week later will develop feeding difficulties, coma, seizures
Treatment of maple syrup urine disease
Dietary leucine restriction
What is homocystinuria?
- Autosomal recessive d/o of metabolism
- Deficiency of CBS (enzyme)
- 50% of untreated pts are mentally retarded
Treatment of homocystinuria
- Large oral doses of pyridoxine (50% respond)
- Females must avoid OCPs (higher risk for coagulopathy)
What is nonketotic hyperglycinemia?
- Autosomal recessive d/o of metabolism
- Deficiency of glycine cleavage enzyme subunits
- Most pts will develop severe mental retardation and seizures
- Treat w/Na benzoate and dextromethorphan (or ketamine)
Define organic acidemia
- Disorders of AA and FA metabolism
- Nonamino organic acids accumulate in serum and urine
(example: maple syrup urine disease)
Example of an organic acidemia?
Maple syrup urine disease
How are fatty acid oxidation disorders treated?
Prevention of hypoglycemia (avoid prolonged fasting 8-12 hrs)
What is Smith-Lemli-Opitz syndrome?
- Autosomal recessive d/o of metabolism
- Deficiency of an enzyme
How do disorders of neurotransmitter metabolism present?
- Movement disorders
- Seizures
- Abnormal tone
- Mental retardation
Between birth and 4 months, what accounts for 40% of weight gain?
Fat
Between birth and 4 months, fat accounts for how much weight gain? How much between 24-36 months, ideally?
40% in infancy
Only 3% from 24-36 months
What are reliable indices of caloric needs in most healthy children?
Appetite and growth
What does optimal growth of an infant require?
Adequate dietary supply of protein (body does not store protein)
As growth decreases, so does the need for:
Protein
When do protein needs decrease?
As growth rates decrease
When do protein needs increase?
- Skin or gut losses
- Burns
- Traumas
- Infections
What is the main dietary energy source for infants?
Fats
What accounts for 50% of the energy in human milk?
Fats
What are fats required for in infant development?
- Myelination of CNS
- Brain development
How much dietary fat should children over 2 yo intake?
Decrease to 30% calories from fat (main source as an infant)
Clinical presentation of omega 6 deficiency in infants
-Growth failure
-Erythematous and scaly dermatitis
-Thrombocytopenia
etc etc
Most fatty acids in breast milk are:
Omega 6
Clinical presentation of omega 3 deficiency in infants
Less defined than omega 6 deficiency
- Dermatitis
- Neuro abnormalities (blurred vision, peripheral neuropathy, weakness)
Lactose in breast milk compared to cow’s milk
- 40% of caloric intake in breast milk is lactose
- 20% in cow’s milk
Lactase levels in infancy?
Highest in infancy, decline with age
When are lactase levels highest?
In infancy - decline with age
After age 2, most of caloric intake should be what?
Carbs (50-60% of intake) but NOT more than 10% simple sugars
Describe fructose
- Real problem for our diet
- Does NOT stimulate insulin secretion or enhance leptin production
- So may contribute to increased energy intake and weight gain
What are fat soluble vitamins?
A D E K
deficiencies occur more slowly due to body storage with fat
What is Vitamin D needed for?
Ca absorption
Benefits of breast feeding
- Immunologic factors
- Protection against URIs, GI infections
- Decreases risk of atopic dermatitis and cow’s milk allergy
- Maternal calories used (help to get to pre-pregnancy wt)
- Mother/baby bonding (uninterrupted time)
When is the fastest growth as a child? What is the growth rate?
1st year
- Body wt doubles by 3-4 mos
- Triples by 12 months
Contraindications to breast feeding
RARE
- TB in mother
- Galactosemia
Potential risk of breast feeding
Maternal to child HIV transmission (if cracking of nipple causes blood exposure)
-In undeveloped countries, the protection against diarrhea and malnutrition outweigh the risk
Obstacles that mothers face with breast feeding
- Difficult to do once returning to work
- Meds can be passed through the milk
- Social barriers (public areas, space available)
Using formula instead of breast feeding?
- Acceptable alternative
- BUT at least attempt breast feeding the first couple weeks for the immunologic benefits
Delaying the introduction of certain foods past 6 months to prevent allergies, eczema or asthma?
NOT been shown to prevent any of these
When do infants start to use finger foods (pincer grasp)?
7-10 months
How many exposure attempts can it take before an infant accepts a new food?
Sometimes takes 10-15 attempts
Define failure to thrive
Weight curve has fallen by 2 major percentile channels OR weight for length decreases below 5th percentile
Define wasting
Reduced weight for height
Define stunting
Reduction in height for age with chronic malnutrition
What should always be considered with undernutrition?
Neglect, abuse, mental illness
What could tube feedings in underweight infants cause?
Over-satiation - which will likely delay transition to oral nutrition
If TPN in an infant is necessary, what should be done?
Every effort made to provide at least a minimum of nutrients ENTERALLY (to preserve integrity of GI mucosa and function)
Why should enteral nutrition always be considered first over TPN?
It preserves GI mucosa and function
