• Turnaround time:
    10–21 calendar days (14 days on average)
  • Preferred specimen:
    3mL whole blood in a purple-top tube
  • Alternate specimens:
    DNA or saliva/assisted saliva
  • Sample requirements
  • Request a sample kit



ACP33; BM-019; GL010; MAST

Associated disorders

The SPG21 gene (also known as ACP33), is associated with autosomal recessive hereditary spastic paraplegia 21 (SPG21), also known as Mast syndrome (MedGen UID: 343325).

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Invitae tests that include this gene:

SPG21 is a rare cause of autosomal recessive HSP, and the percentage of cases attributed to pathogenic variants identified in SPG21 is unknown.

The SPG21 gene encodes the acidic cluster protein, 33-KD, also known as maspardin, which interacts with the CD4 glycoprotein in immune cells and has been implicated in the regulation of T-cell activation. Additionally, SPG21-deficient mice have progressive hind limb dysfunction, and cultured neurons from these mice show increased axon branching.

Assay and technical information

Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).

Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence in the transcript listed below. In addition, analysis covers the select non-coding variants specifically defined in the table below. Any variants that fall outside these regions are not analyzed. Any specific limitations in the analysis of these genes are also listed in the table below.

Our analysis detects most intragenic deletions and duplications at single exon resolution. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. If you are requesting the detection of a specific single-exon copy number variation, please contact Client Services before placing your order.

Gene Transcript reference Sequencing analysis Deletion/Duplication analysis
SPG21 NM_016630.6