An inherited enzyme deficiency leading to the disruption of normal bodily metabolism.
Accumulation of a toxic substrate.
Impaired formation of a product normally produced by the deficient enzyme.
3. An inherited enzyme deficiency leading to the
disruption of normal bodily metabolism.
Accumulation of a toxic substrate.
Impaired formation of a product normally
produced by the deficient enzyme.
Garrod`s hypothesis :-
A B C
D
substrate excess product deficiency
toxic metabolite
7. Index of suspicion
Family History
Have a child already affected by an inherited
disorder.
One of the parents affected by autosomal or X-
linked disorder.
H/O Neonatal deaths, fetal losses
Maternal family history
males - X-linked disorders
all - mitochondrial DNA is maternally
inherited
A positive family history may be helpful!
8. Enzymatic assay of cultured amniocytes
Chorionic villi sampling to determine the
chromosomal,enzymatic or molecular genetic
status of the fetus.
Cytogenetics
Enzyme assay.
10. Reliable screen test and low false negative
results.
Test is simple and inexpensive
Available results soon to start effective
therapy
Definite follow up test
Outcome without treatment is very bad
Effective therapy is available
11. Index of suspicion
“with any full-term infant who has no antecedent
maternal fever or PROM (premature rupture of
the membranes) and who is sick enough to
warrant a blood culture or LP, one should proceed
with a family history & few simple lab tests.
12. Family History
Most IEM’s are recessive - a negative family
history is not reassuring!
Consanguinity, ethnicity, inbreeding
neonatal deaths, fetal losses
maternal family history
males - X-linked disorders
all - mitochondrial DNA is maternally inherited
A positive family history may be helpful!
16. GalactosemiaGalactosemia
Enzyme deficiency:-
Galactose-1-p uridyl transferase
Galactokinase
Uridine diphosphate galactose 4 epimerase
Screening :-
Failure to thrive
Hypoglycemia
Urine demonstrates the presence of
reducing substance that does not react to glucose
oxidase.
Galactose can be identified by
chromatography.
Galactose & galactose-1-p in blood
Confirmed :-
Assaying red blood cell transferase activity.
20. Glycogen Storage DisordersGlycogen Storage Disorders
Type 1-Von Gierke’s
Enzyme deficiency:-
Glucose-6-phosphatase
Screening :-
Life threatening
Hypoglycemia
Lactic acidosis
Hyper-uricemia
Hyper lipidemia
Adverse response to Glucagon with worsening Lactic acidosis.
Confirmed :-
Glucose-6-phosphatase enzyme activity
assay in liver biopsy.
21. Enzyme deficiency:-
Type 2- Pompe’s disease- Acid α-glucosidase
Type 3- Deficency of Glycogen debranching enzyme
Type 4- Deficiency of Branching enzyme
Type 5- McArdle`s Syndrome- Muscle phosphorylase
Type 6- Liver phosphorylase or phosphorylase kinase
Screening :-
Almost same as type I
Confirmed :-
Respective enzyme activity assay in liver & muscle biopsy.
22. Mucopolysacccharidosis
Mutation in a gene encoding a lysosomal hydrolase
involved in the degradation of 1 or more GAGs
Defective lysosomal hydrolase
Accumulation of substates in various tissues including
Liver,spleen,skin,bone & CNS
Hurler syndrome – α l-iduronidase
Hunter syndrome - iduronate sulfatase
• Urinalysis for presence of ↑ GAGs
• Assay of suspected enzymes in WBC,fibroblast or serum
• Tissue biopsy with subsequent analysis of GAG by electrophoresis
• Use of specific gene test
• Prenatal diagnosis by amniotic fluid cells or chorionic villus sampling.
24. Aromatic Amino acid metabolism
Phenylketonuria
Enzyme deficiency:-
Phenylalanine hydroxylase
Dihydrobiopterine reductase
6-Pyruvoyl-tetrahydropterin synthase
GTP cyclohydrolase I
Pterin-4-carbinolamine dehydratase
Screening :- FeCl₃ to detect urinary phenyl pyruvate
Tandem mass spectrometry.
Prenatal Diagnosis :-
DNA probe
Confirmed :-
Elevated blood phenylalanine level.
Enzyme activity
25.
26. Tyrosinemia
Enzyme deficiency:-
Type I- Fumarylacetoacetase
Type II-Tyrosine aminotransferase
Type III-4-hydroxyphenylpyruvate dioxygenase
Screening :-
FeCl₃
Tandem mass spectrometry.
Prenatal Diagnosis :-
RFLP
Confirmed :-
Elevated conc of tyrosine in plasma
Succinyllactone in urine,by product of fumaryl acetoacetic
acid in urine.
27. Maple syrup urine disease
Enzyme deficiency:-
Branched chain ketoacid dehydrogenase complex
Screening :-
Acidosis
Ketotic hypoglycemia
Pancreatitis
Odor of maple syrup
Mixing urine with DNPH
Prenatal Diagnosis :-
DNA analysis
Confirmed :-
Elevated plasma level of Branched chain amino-acids.
2hydroxy valeric acid in urine.
28. Enzyme deficiency:-
Hypermethioninemia- Methionine adenosyl transferase
Homocystenuria - Cysthionine β-synthase
Cystathionuria - Cystathionase
Prenatal Diagnosis :-
DNA analysis
Confirmed :-
Elevated levels of the regarding substrates in
plasma.
30. Disorders of heme metabolism
Mutation in various genes
Abnormalities of the enzymes of the heme synthesis
Accumulation of ALA
& PBG
↓in heme in cell & body fluid
Nuropsychiatric
signs & symtoms
Accumulation of porphyrinogen
In skin & tissues
Sponteneous oxidation of
Porphyrinogen to porphyrin
photosensitivity
Prenatal diagnosis - Appropriate DNA probe
Diagnosis by ↑ corproporphyrin,uroporphyrin,ALA,PBG,protoporphyrin