Metabolic Disorders Flashcards
Most valuable diagnostic tests with metabolic diseases?
Serum amino acids and urine organic acids
What is PKU?
AR disorder, can’t convert phenylalanine to tyrosine (phenylalanine hydroxylase)
Most common presentation of PKU?
Infant with vomiting, irritability, eczematoid rash, and musty odor (also usually fair-haired and fair-skinned); profound intellectual disability if untreated
Symptoms to suggest metabolic?
Sudden onset lethargy, vomiting, apnea, irritability, seizures, afebrile
Important features of organic acidemias (4)?
1) Elevated ammonia (usually)
2) Anion gap acidosis
3) Drunken appearance
4) Ketonuria
Examples of organic acidemias (4)?
1) Methylmalonic acidemia
2) Propionic acidemia
3) Isovaleric acidemia
4) Biotinidase deficiency
Diagnostic test of choice for organic acidemias?
Urine organic acids
Key feature and treatment of isovaleric acidemia?
Odor of sweaty feet (and seizure); protein restriction
Possible treatment for methylmalonic acidemia?
Vitamin B12
Presentation of FA metabolism defects?
Metabolic acidosis, hypoglycemia, +/-hepatomegaly, with fasting (can’t metabolize FA for glucose or ketones)
Diagnosis of FA metabolism defects?
Plasma acylcarnitine profile
Example of urea cycle defects?
Ornithine transcarbamylase deficiency (most common, X-linked)
Presentation of urea cycle defects?
Hyperammonemia, NO acidosis or ketonuria, respiratory alkalosis, lethargy, hypotonia, vomiting, poor feeding
Treatment of urea cycle defects?
IV glucose, reducing protein, +/-arginine
Diagnosis of urea cycle defects?
Urine organic acids
Presentation of galactosemia?
After first meal of lactose–poor feeding failure to thrive, abdominal distension, hypoglycemia, GNR sepsis (E.coli), urine reducing substances (non glucose)
Defect and diagnostic test in galactosemia?
GALT (galactose-1-phosphate uridyltransferase)–G1P accumulates in kidney, liver, brain; diagnosis by measuring GALT activity in RBCs
Treatment of galactosemia?
Galactose-free diet (soy formula)
Long-term complications of galactosemia?
Cataracts (reversible with diet change), intellectual disability, liver disease
Presentation of inherited fructose intolerance?
Seizures just after a meal, child stays away from sweets; jaundice, hepatomegaly, vomiting, lethargy
Treatment of inherited fructose intolerance?
Avoidance of fructose
Hepatomegaly + non-glucose reducing substances in urine =
Galactosemia
Presentation of maple syrup urine disease (MSUD)?
Hypoglycemia, acidosis, increased tone, seizures, first week of life, maple syrup odor from urine
Diagnosis of MSUD?
Increased leucine, isoleucine, and valine in plasma and urine; +alloisoleucine
Drug of choice in refractory hypoglycemia in infants?
Diazoxide (not glucagon)
Mnemonic for symptoms of biotinidase deficiency?
BIO: Bald (alopecia) Itchy rash Out cold (coma, ataxia, neurological signs) (also lactic acidosis)
Treatment of biotinidase deficiency?
Biotin supplementations
Most important tests for hypoglycemia in infants?
Urine ketones and reducing substances
Examples of amino acid metabolism defects (4)?
1) Alcaptonuria
2) Homocystinuria
3) Tyrosinemia
4) PKU
Presentation of alcaptonuria?
Dark urine or diaper (homogentisic acid in urine); early arthritis and heart disease (as adults)
Treatment of alcaptonuria?
Diet low in tyrosine and phenylalanine (tyrosine not degraded well)
Presentation of homocystinuria?
Elevated methionine levels, dislocated lens (posterior), skeletal abnormalities (like Marfan), cognitive deficits, lighter skin/hair/eyes
Difference between homocystinuria and Marfan?
No cognitive deficits in Marfan
Diagnosis of homocystinuria?
Confirming homocysteine in the urine
Treatment of homocystinuria?
Pyridoxine (Vit. B6); may be resistant–use diet high in cystine and low in methionine
Presentation of tyrosinemia?
Corneal ulcerations, plaques, corneal clouding, skin thickening (all caused by tyrosine accumulation)
Treatment of tyrosinemia?
Diet low in tyrosine and phenylalanine
Risks in PKU and pregnancy if not treated BEFORE conception?
Miscarriage, SGA/LBW, microcephaly, CHD, intellectual disability
Treatment for PKU?
Low phenylalanine formula and diet
Risk of over-treatment of PKU?
Phenylalanine deficiency (lethargy, rash, +/-diarrhea)
Examples of mucopolysaccharidoses or MPS (4)?
1) Hurler’s syndrome (MPS Type I)
2) Hunter’s syndrome (MPS Type II)
3) Sanfilippo syndrome (MPS Type III)
4) Morquio syndrome (MPS Type IV)
Common feature of MPS?
Coarse facies
Key points in Hurler’s?
Hirsuitism, HSM, corneal clouding, low alpha-L-iduronidase in WBC, AR
Key points in Hunter’s?
HSM, joint contractures, pebbly skin, low iduronate sulfatase in WBC, NO corneal clouding, X-linked
Key points in Sanfilippo?
No HSM, +cognitive deficits, AR
Key points in Morquio?
Normal IQ, skeletal involvement, corneal clouding
Presentation of von Gierke disease (GSD Type I)?
Hypoglycemia, distended abdomen, hepatomegaly, poor growth, seizures (2/2 hypoglycemia), elevated TG and cholesterol, lactic acidosis (when fasting), hyperuricemia
Treatment of von Gierke disease (GSD Type I)?
Continuous tube feeds, uncooked cornstarch (releases glucose slowly), allopurinol (hyperuricemia)
Presentation of Pompe disease (GSD Type II)?
Hypotonia, FTT, hepatomegaly with macroglossia, cardiomegaly; NOT hypoglycemia and acidosis (actually a lysosomal storage defect)
Presentation of nonketotic hyperglycinemia?
Intractable neonatal seizures, in utero hiccups, acute encephalopathy, no acidosis, no hyperammonemia
Inheritance of familial hypercholesterolemia?
AD (defect in LDL receptor causing LDL deposition–e.g. tendon xanthomas)
Presentation of Farber’s disease?
Cherry red spot in macula, skin nodules, arthralgias (“Farmer’s disease”)
Presentation of Wolman disease?
FTT, hepatosplenomegaly, calcified and enlarged adrenal gland (defect in lipoprotein metabolism–TG and cholesterol deposited in body tissues)
Peril with Wolman disease?
Plasma TG and cholesterol levels are normal; only deposited in tissues abnormally
Inheritance and presentation of Menkes disease?
X-linked; premature delivery, temperature instability, hypotnoia, hypoglycemia, seizures, neurological deterioration
Lab findings in Menkes disease?
Low serum copper and ceruloplasmin (high in intestinal biopsies, but cannot be transported)
Enzyme deficiency in Gaucher disease?
Lysosomal glucocerebrosidase
Presentation of Gaucher disease?
Hepatosplenomegaly, bone pain (osteosclerosis and lytic lesions), and easy bruising (thrombocytopenia); also CNS deterioration in infantile form, none in juvenile form
Enzyme deficiency and inheritance for Fabry disease?
Lysosomal alpha-galactosidase; X-linked (only sphingolipidosis that is X-linked, rest are AR)
Presentation of Fabry disease?
Agniokeratomas, corneal opacities, vascular disease of kidney, heart, and CNS
Treatment of Fabry disease?
Enzyme replacement therapy
Examples of sphingolipidoses (lysomal problems with breaking down sphingolipids)?
1) Gaucher disease
2) Fabry disease
3) Niemann-Pick disease
4) Tay-Sachs disease
Treatment of juvenile Gaucher disease?
Enzyme replacement therapy
Enzyme deficiency in Tay-Sachs disease?
Hexosaminidase A
Presentation of Tay-Sachs disease?
Neurological deterioration late in the first year of life (axial hypotonia, extremity hypertonia, hyperreflexia, exaggerated startle reflex), macular cherry-red spots, seizures, macrocephaly
Enzyme deficiency in Niemann-Pick disease?
Acid sphinogmyelinase
Presentation of Niemann-Pick disease?
CNS deterioration (generally 3-5 years of age), macular cherry-red spot, HSM, cataplexy, narcolepsy
Difference between Niemann-Pick and Tay-Sachs?
Both have cherry red spots, but only Niemann-Pick has HSM
What hematologic abnormalities can be seen with organic acidemias?
Neutropenia and thrombocytopenia
What hematologic abnormality can be seen with von Gierke disease (type 1b)?
Neutropenia
What lab abnormalities are seen with mitochondrial disorders?
Elevated lactate and pyruvate (excess glycolosis)
What enzyme deficiency may be responsible for treatment-resistant “PKU”?
Tetrahydrobiopterin (BH4)