Glycogen Storage Disorder Panel

Last modified: Mar 21, 2018


  • Is a 29 gene panel that includes assessment of non-coding variants
  • Is ideal for patients with a clinical suspicion of glycogen storage disorders or Lafora disease. The genes on this panel are included in the Comprehensive Metabolism Panel.

Analysis methods

  • PLUS
  • SEQ


3-4 weeks

Number of genes


Test code


CPT codes

SEQ 81405
SEQ 81406
SEQ 81407
DEL/DUP 81479


The Blueprint Genetics Glycogen Storage Disorder Panel (test code ME0301):

  • Is a 29 gene panel that includes assessment of selected non-coding disease-causing variants
  • Is available as PLUS analysis (sequencing analysis and deletion/duplication analysis), sequencing analysis only or deletion/duplication analysis only

ICD codes

Commonly used ICD-10 code(s) when ordering the Glycogen Storage Disorder Panel

ICD-10 Disease
E74.00 Glycogen storage disorders
G40.309 Lafora disease

Sample Requirements

  • EDTA blood, min. 1 ml
  • Purified DNA, min. 3μg
  • Saliva (Oragene DNA OG-500 kit)

Label the sample tube with your patient’s name, date of birth and the date of sample collection.

Note that we do not accept DNA samples isolated from formalin-fixed paraffin-embedded (FFPE) tissue.

Some forms of glycogen storage disease (GSD) affect only one tissue type, whereas others affect multiple organ systems. Broadly speaking, the GSDs can be divided into those with hepatic involvement, which manifest mainly as hypoglycemia, and those associated with neuromuscular disease and weakness. The severity of GSDs ranges from fatal in infancy if untreated to mild disorders with a normal lifespan. Lafora disease, one form of myoclonic epilepsy, is characterized by accumulation of Lafora bodies composed of starch-like polyglucosans, which are insufficiently branched and hence insoluble glycogen molecules. Thus, Lafora disease belongs to the GSD and is included to this panel. This panel enables the genetic basis of GSDs to be readily determined in a clinical setting. The estimated disease incidence for all forms of GSD in the United States is approximately 1 in 20,000 – 25,000 births. These disorders are found in all ethnic groups; different GSD types are enriched in certain populations due to founder mutations. The majority of GSDs are inherited in an autosomal recessive manner. However, two forms of GSD are inherited in an X-linked recessive manner.

Genes in the Glycogen Storage Disorder Panel and their clinical significance

Gene Associated phenotypes Inheritance ClinVar HGMD
AGL Glycogen storage disease AR 82 242
ALDOA Glycogen storage disease AR 2 8
ENO3 Glycogen storage disease AR 3 4
EPM2A Epilepsy, progressive myoclonic AR 15 74
FBP1 Fructose-1,6-bisphosphatase deficiency AR 18 41
G6PC Glycogen storage disease AR 33 112
GAA Glycogen storage disease AR 136 528
GBE1 Glycogen storage disease AR 30 71
GYG1 Glycogen storage disease AR 8 11
GYS1 Glycogen storage disease AR 5 5
GYS2 Glycogen storage disease AR 14 22
LAMP2 Danon disease XL 54 94
LDHA Glycogen storage disease AR 1 8
NHLRC1 Epilepsy, progressive myoclonic AR 14 70
PFKM Glycogen storage disease AR 11 26
PGAM2 Glycogen storage disease AR 3 9
PGK1 Phosphoglycerate kinase 1 deficiency XL 15 26
PGM1 Congenital disorder of glycosylation AR 9 30
PHKA1 Glycogen storage disease XL 6 8
PHKA2 Glycogen storage disease XL 22 113
PHKB Glycogen storage disease AR 8 24
PHKG2 Glycogen storage disease AR 7 31
PRKAG2# Hypertrophic cardiomyopathy (HCM), Wolff-Parkinson-White syndrome, Glycogen storage disease of heart, lethal congenital AD 19 53
PRKAG3 Increased glyogen content in skeletal muscle AD 1 1
PYGL Glycogen storage disease AR 20 43
PYGM Glycogen storage disease AR 62 153
RBCK1 Polyglucosan body myopathy AR 8 14
SLC2A2 Glycogen storage disease, Fanconi-Bickel syndrome, Neonatal diabetes mellitus AR 17 71
SLC37A4 Glycogen storage disease AR 27 108

* Some, or all, of the gene is duplicated in the genome. Read more.

# The gene has suboptimal coverage (means <90% of the gene’s target nucleotides are covered at >20x with mapping quality score (MQ>20) reads).

The sensitivity to detect variants may be limited in genes marked with an asterisk (*) or number sign (#)

Gene refers to the HGNC approved gene symbol; Inheritance refers to inheritance patterns such as autosomal dominant (AD), autosomal recessive (AR), X-linked (XL), X-linked dominant (XLD) and X-linked recessive (XLR); ClinVar refers to the number of variants in the gene classified as pathogenic or likely pathogenic in this database (ClinVar); HGMD refers to the number of variants with possible disease association in the gene listed in Human Gene Mutation Database (HGMD). The list of associated, gene specific phenotypes are generated from CGD or Orphanet databases.

Non-coding variants covered by the panel

Gene Genomic location HG19 HGVS RefSeq RS-number
AGL Chr1:100381954 c.4260-12A>G NM_000028.2 rs369973784
GAA Chr17:78078369 c.-17C>T NM_000152.3
GAA Chr17:78078341 c.-32-13T>A NM_000152.3
GAA Chr17:78078341 c.-32-13T>G NM_000152.3 rs386834236
GAA Chr17:78078352 c.-32-2A>G NM_000152.3
GAA Chr17:78078351 c.-32-3C>A NM_000152.3
GAA Chr17:78078351 c.-32-3C>A/G NM_000152.3
GAA Chr17:78082266 c.1076-22T>G NM_000152.3 rs762260678
GAA Chr17:78092432 c.2647-20T>G NM_000152.3
GBE1 Chr3:81542963 c.2053-3358_2053-3350delGTGTGGTGGinsTGTTTTTTACATGACAGGT NM_000158.3
GYG1 Chr3:148717967 c.481+3276C>G NM_004130.3
LAMP2 ChrX:119604078 c.-1054A>C NM_001122606.1
PFKM Chr12:48535459 c.1626-64A>G NM_001166686.1
PGM1 Chr1:64113966 c.1199-222G>T NM_001172818.1
PGM1 Chr1:64124734 c.1654-523G>A NM_001172818.1
PHKG2 Chr16:30762416 c.96-11G>A NM_000294.2 rs751600886
PYGM Chr11:64525847 c.425-26A>G NM_005609.2 rs764313717
PYGM Chr11:64523631 c.661-601G>A NM_005609.2
SLC2A2 Chr3:170745041 c.-582A>C NM_000340.1

Added and removed genes from the panel

Genes added Genes removed

Test strength

The strengths of this test include:
  • CAP and ISO-15189 accreditations covering all operations at Blueprint Genetics including all Whole Exome Sequencing, NGS panels and confirmatory testing
  • CLIA-certified personnel performing clinical testing in a CLIA-certified laboratory
  • Powerful sequencing technologies, advanced target enrichment methods and precision bioinformatics pipelines ensure superior analytical performance
  • Careful construction of clinically effective and scientifically justified gene panels
  • Our Nucleus online portal providing transparent and easy access to quality and performance data at the patient level
  • Our publically available analytic validation demonstrating complete details of test performance
  • 1479 non-coding disease causing variants in Blueprint WES assay (please see below ‘Non-coding disease causing variants covered by this panel’)
  • Our rigorous variant classification based on modified ACMG variant classification scheme
  • Our systematic clinical interpretation workflow using proprietary software enabling accurate and traceable processing of NGS data
  • Our comprehensive clinical statements

Test limitations

The following exons are not included in the panel as they are not sufficiently covered with high quality sequence reads: PRKAG2 (10, 13). Genes with suboptimal coverage in our assay are marked with number sign (#). Gene is considered to have suboptimal coverage when >90% of the gene's target nucleotides are not covered at >20x with mapping quality score (MQ>20) reads. The technology may have limited sensitivity to detect variants in genes marked with these symbols (please see the Panel content table above).

This test does not detect the following:
  • Complex inversions
  • Gene conversions
  • Balanced translocations
  • Mitochondrial DNA variants
  • Repeat expansion disorders unless specifically mentioned
  • Non-coding variants deeper than ±20 base pairs from exon-intron boundary unless otherwise indicated (please see above Panel Content / non-coding variants covered by the panel).

This test may not reliably detect the following:

  • Low level mosaicism
  • Stretches of mononucleotide repeats
  • Indels larger than 50bp
  • Single exon deletions or duplications
  • Variants within pseudogene regions/duplicated segments

The sensitivity of this test may be reduced if DNA is extracted by a laboratory other than Blueprint Genetics.

For additional information, please refer to the Test performance section and see our Analytic Validation.

The Blueprint Genetics glycogen storage disorder panel covers classical genes associated with glycogen storage disorders and Lafora disease. The genes on the panel have been carefully selected based on scientific literature, mutation databases and our experience.

Our panels are sliced from our high-quality whole exome sequencing data. Please see our sequencing and detection performance table for different types of alterations at the whole exome level (Table).

Assays have been validated for different starting materials including EDTA-blood, isolated DNA (no FFPE), saliva and dry blood spots (filter card) and all provide high-quality results. The diagnostic yield varies substantially depending on the assay used, referring healthcare professional, hospital and country. Blueprint Genetics' Plus Analysis (Seq+Del/Dup) maximizes the chance to find a molecular genetic diagnosis for your patient although Sequence Analysis or Del/Dup Analysis may be a cost-effective first line test if your patient's phenotype is suggestive of a specific mutation type.

Performance of Blueprint Genetics Whole Exome Sequencing (WES) assay. All individual panels are sliced from WES data.

Sensitivity % (TP/(TP+FN) Specificity %
Single nucleotide variants 99.65% (412,456/413,893) >99.99%
Insertions, deletions and indels by sequence analysis
1-10 bps 96.94% (17,070/17,608) >99.99%
11-50 bps 99.07% (957/966) >99.99%
Copy number variants (exon level dels/dups)
Clinical samples (small CNVs, n=52)
1 exon level deletion 92.3% (24/26) NA
2 exons level deletion/duplication 100.0% (11/11) NA
3-7 exons level deletion/duplication 93.3% (14/15) NA
Microdeletion/-duplication sdrs (large CNVs, n=37))
Size range (0.1-47 Mb) 100% (37/37)
Simulated CNV detection
2 exons level deletion/duplication 90.98% (7,357/8,086) 99.96%
5 exons level deletion/duplication 98.63% (7,975/8,086) 99.98%
The performance presented above reached by WES with the following coverage metrics
Mean sequencing depth at exome level 174x
Nucleotides with >20x sequencing coverage (%) 99.4%


The target region for each gene includes coding exons and ±20 base pairs from the exon-intron boundary. In addition, the panel includes non-coding variants if listed above (Non-coding variants covered by the panel). Some regions of the gene(s) may be removed from the panel if specifically mentioned in the ‘Test limitations” section above. The sequencing data generated in our laboratory is analyzed with our proprietary data analysis and annotation pipeline, integrating state-of-the art algorithms and industry-standard software solutions. Incorporation of rigorous quality control steps throughout the workflow of the pipeline ensures the consistency, validity and accuracy of results. Our pipeline is streamlined to maximize sensitivity without sacrificing specificity. We have incorporated a number of reference population databases and mutation databases such as, but not limited, to 1000 Genomes Project, gnomAD, ClinVar and HGMD into our clinical interpretation software to make the process effective and efficient. For missense variants, in silico variant prediction tools such as SIFT, PolyPhen, MutationTaster are used to assist with variant classification. Through our online ordering and statement reporting system, Nucleus, the customer has an access to details of the analysis, including patient specific sequencing metrics, a gene level coverage plot and a list of regions with inadequate coverage if present. This reflects our mission to build fully transparent diagnostics where customers have easy access to crucial details of the analysis process.

Clinical interpretation

We provide customers with the most comprehensive clinical report available on the market. Clinical interpretation requires a fundamental understanding of clinical genetics and genetic principles. At Blueprint Genetics, our PhD molecular geneticists, medical geneticists and clinical consultants prepare the clinical statement together by evaluating the identified variants in the context of the phenotypic information provided in the requisition form. Our goal is to provide clinically meaningful statements that are understandable for all medical professionals regardless of whether they have formal training in genetics.

Variant classification is the corner stone of clinical interpretation and resulting patient management decisions. Our classifications follow the Blueprint Genetics Variant Classification Schemes based on the ACMG guideline 2015. Minor modifications were made to increase reproducibility of the variant classification and improve the clinical validity of the report. Our experience with tens of thousands of clinical cases analyzed at our laboratory allowed us to further develop the industry standard.

The final step in the analysis of sequence variants is confirmation of variants classified as pathogenic or likely pathogenic using bi-directional Sanger sequencing. Variant(s) fulfilling all of the following criteria are not Sanger confirmed: 1) the variant quality score is above the internal threshold for a true positive call, 2) an unambiguous IGV in-line with the variant call and 3) previous Sanger confirmation of the same variant at least three times at Blueprint Genetics. Reported variants of uncertain significance are confirmed with bi-directional Sanger sequencing only if the quality score is below our internally defined quality score for true positive call. Reported copy number variations with a size <10 exons are confirmed by orthogonal methods such as qPCR if the specific CNV has been seen less than three times at Blueprint Genetics.

Our clinical statement includes tables for sequencing and copy number variants that include basic variant information (genomic coordinates, HGVS nomenclature, zygosity, allele frequencies, in silico predictions, OMIM phenotypes and classification of the variant). In addition, the statement includes detailed descriptions of the variant, gene and phenotype(s) including the role of the specific gene in human disease, the mutation profile, information about the gene’s variation in population cohorts and detailed information about related phenotypes. We also provide links to the references used, congress abstracts and mutation databases to help our customers further evaluate the reported findings if desired. The conclusion summarizes all of the existing information and provides our rationale for the classification of the variant.

Identification of pathogenic or likely pathogenic variants in dominant disorders or their combinations in different alleles in recessive disorders are considered molecular confirmation of the clinical diagnosis. In these cases, family member testing can be used for risk stratification within the family. In the case of variants of uncertain significance (VUS), we do not recommend family member risk stratification based on the VUS result. Furthermore, in the case of VUS, we do not recommend the use of genetic information in patient management or genetic counseling. For eligible cases, Blueprint Genetics offers a no charge service to investigate the role of reported VUS (VUS Clarification Service).

Our interpretation team analyzes millions of variants from thousands of individuals with rare diseases. Thus, our database, and our understanding of variants and related phenotypes, is growing by leaps and bounds. Our laboratory is therefore well positioned to re-classify previously reported variants as new information becomes available. If a variant previously reported by Blueprint Genetics is re-classified, our laboratory will issue a follow-up statement to the original ordering health care provider at no additional cost.