Biochemical Genetics

Section Director:

Lisa Kratz, Ph.D.

 

kratz@kennedykrieger.org

 

Phone: 443-923-2782

 

Fax: 443-923-2781

Assistant Section Director:

Jessica Albert, Ph.D.

 

albertj@kennedykrieger.org

 

Phone: 443-923-2782

 

Fax: 443-923-2781

The Biochemical Genetics Section of the Genetics Laboratories assays blood, urine, fibroblasts and amniotic fluid for inborn errors of metabolism associated with diseases such as propionic acidemia, phenylketonuria, Canavan’s disease, Barth’s disease, Smith-Lemli-Opitz syndrome and other disorders of fatty acid oxidation and organic acid metabolism. Our assays are performed on gas chromatography/mass spectrometry and tandem mass spectrometry platforms.

Indications for Biochemical Genetics Screening

The criteria for testing for inborn errors of metabolism is very broad. The following is a list of some characteristic features/symptoms, usually evident in the early childhood period.

  • Distinctive facial features
  • Hypotonia
  • Short stature, stippled epiphyses
  • Malformations of organs/genitalia
  • Learning/behavioral problems
  • Intellectual Disability
  • Feeding Difficulties
  • Micro/macrocephaly
  • Seizures
  • Failure to thrive

Biochemical Genetics Tests

Organic Acids
Organic acids from urine are identified by gas chromatography/mass spectrometry and the values compared to normal and disease control values. (Propionic academia (PROP), GKD, GA)
Amino Acid Analysis
Plasma from heparin-treated whole blood is used to identify and quantitate amino acids using an Amino Acid Detector and ninhydrin-based detection. (PKU, MSUDIA, Tyrosinemia)
Carnitine, Free and Total
Plasma from EDTA-treated or heparin-treated whole blood is analyzed by tandem mass spectrometry. (CDSP, renal carnitine transport defect)
Acylcarnitine Profile
Plasma from EDTA-treated or heparin-treated whole blood is analyzed by tandem mass spectrometry
N-acetyl-L-aspartate
Urine is analyzed by gas chromatography/mass spectrometry. (Canavan Disease)
3-Methylglutaconic Acid
Urine or plasma from EDTA-treated or heparin-treated whole blood is analyzed by gas chromatography/mass spectrometry. (Barth Syndrome)
Orotic Acid Analysis
Urine is analyzed by gas chromatography/mass spectrometry (Urea cycle disorders)
Methylmalonic Acid (MMA)
Urine is analyzed by tandem mass spectrometry. (Vitamin B12 deficiency)
Mevalonate
Urine is analyzed by gas chromatography/mass spectrometry. (Mevalonic aciduria, Hyper IgD)
Cholestanol
Plasma from EDTA-treated or heparin-treated whole blood is analyzed by gas chromatography/mass spectrometry. (Cerebrotendinous xanthomatosis)
Sitosterol
Plasma from EDTA-treated or heparin-treated whole blood is analyzed by gas chromatography/mass spectrometry. (Sitosterolemia)
Guanidinoacetic acid + creatinine
Plasma from EDTA-treated or heparin-treated whole blood or fasting urine is analyzed by gas chromatography/mass spectrometry. (Renal metabolism)
8(9)-Cholestenal
Plasma from EDTA-treated or heparin-treated whole blood is analyzed by gas chromatography/mass spectrometry. (Chondrodysplasia punctata, Type 2)
  • Cholesterol biosynthesis intermediates:
    • 7-Dehydrocholesterol (Smith-Lemli-Opitz syndrome)
    • Lathosterol
    • Desmosterol

Prenatal Testing

We can test cultured amniocytes for the presence of biochemical genetic disorders such as Canavan Disease and Smith-Lemli-Opitz syndrome. Results are compared to our normal and disease control values.

Tests by arrangement include:

CHILD syndrome Antley-Bixler syndrome Greenberg dysplasia
Full sterol pathway   Tissue sterol analysis