Mutations and deletions of the GK gene (Xp21.3) cause glycerol kinase deficiency (GKD). GKD can be part of a contiguous gene syndrome or occur as isolated GKD. The isolated form can either be symptomatic or asymptomatic. Isolated symptomatic GKD presents in early childhood with episodes of metabolic (vomiting and acidosis) and central nervous system (CNS) (lethargy and coma) decompensation. Additionally, individuals with the symptomatic GKD were reported to have intellectual disability, developmental delay, and/or seizures. Isolated asymptomatic GKD presents with hyperglycerolemia and glyceroluria but do not have the episodes of metabolic and CNS decompensation.
Complete loss of GK activity, caused by GK gene deletions and nonsense mutations, is typically associated with the symptomatic form of GKD. GK gene missense mutations that result in residual GK enzyme activity may or may not result in the symptomatic form of GKD.
GKD as part of a contiguous gene syndrome can include the DAX1 gene, which is responsible for adrenal hypoplasia congenital, the DMD gene, which causes Duchenne muscular dystrophy, and/or the OTC gene, which is responsible for ornithine transcarbamylase deficiency. The contiguous gene syndrome can be detected by array comparative genomic hybridization (aCGH).
- Confirmation of a clinical diagnosis of Glycerol Kinase Deficiency in an individual in whom sequence analysis was negative.
- Carrier testing in adults with a family history of Glycerol Kinase Deficiency in whom sequence analysis was negative.
Please note that a "backbone" of probes across the entire genome are included on the array for analytical and quality control purposes. Rarely, off-target copy number variants causative of disease may be identified that may or may not be related to the patient's phenotype. Only known pathogenic off-target copy number variants will be reported. Off-target copy number variants of unknown clinical significance will not be reported.
Submit only 1 of the following specimen types
Preferred specimen type: Whole Blood
Type: Whole Blood
Specimen Requirements:In EDTA (purple top) tube:
Infants (<2 years): 2-3 ml
Children (>2 years): 3-5 ml
Older Children & Adults: 5-10 ml
Specimen Collection and Shipping: Refrigerate until time of shipment. Ship sample within 5 days of collection at room temperature with overnight delivery.
Specimen Requirements:OrageneTM Saliva Collection kit (available through EGL) used according to manufacturer instructions.
Specimen Collection and Shipping: Store sample at room temperature. Ship sample within 5 days of collection at room temperature with overnight delivery.
- Sequence analysis of the GK gene is available and is required before deletion/duplication analysis.
- Chromosomal Micrcoarray EmArray 60K
- Custom diagnostic mutation analysis (KM) is available to family members if mutations are identified by targeted mutation testing or sequencing analysis.
- Prenatal testing is available only for known familial mutations to individuals who are confirmed carriers of mutations. Please contact the laboratory genetic counselor to discuss appropriate testing prior to collecting a prenatal specimen.
- X-Linked Intellectual Disability panels are available for 30, 60, and 90 genes.