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Flashcards in inborn errors in metabolism Deck (48)
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When it is ok to do Mass screening for illnesses? (7)

- Dz is common and serious enough to be worth it
- There is a pre-Sx impact (knowing would change the course of the dz)
- ID of risk does not result in discrimination
- Early Tx is available
- Test has specificity (low false +) and sensitivity (low false -)
- Available for everyone
- Cost/benefit


Suspect an inborn error of metabolism when? (8)

• Sx with changes in diet
• Development of child decreases (all declines need a full work-up)
• Specific food aversions
• FH retardation or unexplained deaths
• Appear sepsis
• Recurrent hypoglycemia
• Neuro Sx don’t follow patterns
• Unexplained acidosis


D/o of toxic accumulation (precursers that cause toxicity) (3)

a. Protein metabolism d/o
b. Carb intolerance
c. Lysosomal storage d/o


2 Categories of inborn error of metabolism?

1. D/o of toxic accumulation (precursers that cause toxicity)
2. D/o of E production/utilization


D/o of E production/utilization (4)

a. Fatty acid oxidation defects
b. Carb utilization or production d/o
c. Mitochondrial d/o
d. Perioxisomal d/o



• Amino acid metabolism d/o (hyperphenylalaninemia) (enzyme d/o)
• Autosomal recessive


Presentation of Phenylketonuria

o Severe MR
o Hyperactivity
o Seizures
o Light complexion, blond hair, eczema


Treatment of Phenylketonuria

o Emilination diet in 1st mo of life
o Phenylalanine LOW diets to allow normal growth
o Regulate mother before and during birth



• Near total deficiency of galactose 1-p uridyltransferase (enzyme)
• Autosomal recessive


Presentation of Galactosemia

o Neonate vomiting, jaundice, hepatomegaly, rapid liver insufficiency after the initiation of milk feeding
o Progressive cirrhosis


Treatment of Galactosemia

o Prompt galactose-free diet
• Liver Dz prognosis is good
• Speech, ovarian, language prognosis not so good
o Ca2+ supplements


Maple Syrup Urine Disease

• D/t deficiency of decarboxylation enzyme for keto acids (leucine, isoleucine, valine)
• Autosomal recessive


Presentation of Maple Syrup Urine Disease

o Normal at birth
o One week later: feeding difficulties, coma, seizures
o Most die in 1st mo w/no diet restriction


Treatment of Maple Syrup Urine Disease

o Dietary leucine restriction
o Catabolism avoidance (don’t diet)



• Deficiency of CBS (enzyme)
• Autosomal recessive
• Untreated → 50% MR


Presentation of Homocystinuria

o Looks like Marfans dz
o Arachnodactyly (spider fingers)
o Osteoporosis and dislocated lenses
o Thromboembolic phenomena (OCP risk later)


Treatment of Homocystinuria

o Lg oral doses of pyridoxine
o Non-responders Tx with methionine restrictions
o Avoidance of OCPs (coag risk)


Nonketotic Hyperglycemia

• Deficiency of glycine enzyme
• Autosomal recessive
• Most develop MR and seizures


Presentation of Nonketotic Hyperglycemia

o Hypotonia, lethargy
o Developmental delays, chorea later


Treatment for Nonketotic Hyperglycemia

o Sodium benzoate (preservative) and dextromethorphan or ketamine


Organic Acidemias

• Amino/fatty acid metabolism d/o which causes accumulation of nonamino organic acids accumulate in serum and urine
• Autosomal recessive


Fatty acid oxidation disorder

• Difficulty breaking down long fatty acid chains
• Presentation
o Reye-like episodes
o HypOketotic, hypOglycemia
o HypERammonemia
o Hepatomegaly, encephalopathy


Treatment for Fatty acid oxidation disorder

o Avoid prolonged fasting (to prevent hypOglycemia)


Smith-Lemli-Opitz Syndrome

• Autosomal recessive
• Enzyme deficiency


Presentation of Smith-Lemli-Opitz Syndrome

o Microcephaly, poor growth, MR
o Dysmorphic face and extremities
o Malformations of the heart/GU


Treatment for Smith-Lemli-Opitz Syndrome

o No prenatal Tx
o Add cholesterol for growth


Disorders of Neurotransmitter Metabolism

• Mvmt, seizures, tone, MR or CP
• Dx: CSF
• Tx: serine and glycine


Random facts about growth rate and being fed

Infancy has the highest growth rate (double in first 4 months)
• Brain = 10% body weight/44% E consumer
• Fat = 40% body weight (drops to 3% at 24mo)
1st 3 mo: Breast fed babies exceed formula fed
6-12mo: Breast fed babies weigh less than formula fed


Nutritional Requirements for Protein (5)

• Not stored in the body! Dietary supply needed
• Needed for growth (immune and GI)
• 80% protein needed in preemies/20% in term in 1yo
• Excess is not harmful
• Increases needed in skin/gut damage, burns, trauma, infection


Nutritional Requirements for Lipids (4)

• Main energy source (50% cal from fat in 1st year/ >2 30% cal from fat)
• 50% of the E in human milk
• Required for absorption of fat soluable vits (ADEK)
• Required for myelination of CNS/brain development