ML IIIC , which is clinically indistinguishable from ML IIIA, is characterized by short stature, skeletal abnormalities (mild to moderate dysostosis multiplex, joint stiffness), cardiomegaly, mild coarsening of facial features and developmental delay. In patients with ML IIIC, the activity of nearly all lysosomal hydrolases is up to tenfold higher in plasma and other body fluids than in normal controls due to inadequate targeting of GlcNAc-1-PT to lysosomes.
For patients with suspected ML IIIC, sequence analysis is recommended as the first step in pathogenic variant identification. For patients in whom pathogenic variants are not identified by full gene sequencing, deletion/duplication analysis is appropriate.
- OMIM #252605: Mucolipidosis III gamma
- OMIM #607838: GNPTG gene
- Kudo et al (2006). Am. J. Hum. Genet. 78:451-463.
- Confirmation of a clinical diagnosis of ML IIIC.
- Carrier testing in adults with a family history of ML IIIC.
Analytical Sensitivity: ~99%
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: Please do not refrigerate or freeze saliva sample. Please store and ship at room temperature.
- Deletion/duplication analysis of the GNPTG gene by CGH array is available for those individuals in whom sequence analysis is negative.
- Sequencing and deletion/duplication analysis is available for ML IIIA.
- Custom diagnostic analysis for pathogenic variants or variants of unknown clinical significance (test code: KM) is available to family members if pathogenic variants or variants of unknown clinical significance are identified by targeted testing or sequencing analysis.
- Prenatal testing is available only for known familial pathogenic variants to individuals who are confirmed carriers of pathogenic variants. Please contact the laboratory genetic counselor to discuss appropriate testing prior to collecting a prenatal specimen.