Clinical symptoms may be noticeable from infancy and may include: congenital dislocation of the hip, thoracic deformities, hernia, and hyperplastic gums which are evident soon after birth. Other symptoms may include delayed psychomotor development, clear corneas, and restricted joint mobility.
Mutations in the GNPTAB gene cause a deficiency of the enzyme GlcNAc-1-P. Diagnostic sequencing analysis of the GNPTAB gene coding region is available for mucolipidosis II patients and their at-risk relatives on a clinical basis. For patients with mutations not identified by full gene sequencing, a separate deletion/duplication assay is available using a targeted CGH array (LJ).
For questions about testing for ML II, call EGL Genetics at (470) 378-2200 or (855) 831-7447. For further clinical information about lysosomal storage diseases, including management and treatment, call the Emory Lysosomal Storage Disease Center at (404) 778-8565 or (800) 200-1524.
1. Leroy JG, Spranger JW. I-cell disease. N Engl J Med. 1970 Sep 10;283(11):598-9.
2. Kudo M, Brem MS, Canfield WM: Mucolipidosis II (I-cell disease) and mucolipidosis IIIA (classical pseudo-Hurler polydystrophy) are caused by mutations in the GlcNAc-phosphotransferase alpha/beta-subunits precursor gene. Am. J. Hum. Genet. 78: 451-463, 2006.
3. Olkkonen VM, Ikonen E. Genetic defects of intracellular-membrane transport. New Eng. J. Med. 343: 1095-1104, 2000.
4. Tiede S, Storch S, Lubke T, Henrissat B, Bargal R, Raas-Rothschild A, Braulke T. Mucolipidosis II is caused by mutations in GNPTA encoding the alpha/beta GlcNAc-1-phosphotransferase. Nature Med. 11: 1109-1112, 2005.
5. Paik, K. H.; Song, S. M.; Ki, C. S.; Yu, H.-W.; Kim, J. S.; Min, K. H.; Chang, S. H.; Yoo, E. J.; Lee, I. J.; Kwan, E. K.; Han, S. J.; Jin, D.-K. Identification of mutations in the GNPTA (MGC4170) gene coding for GlcNAc-phosphotransferase alpha/beta subunits in Korean patients with mucolipidosis type II or type IIIA. Hum. Mutat. 26: 308-314, 2005.
- Confirmation of clinical diagnosis of ML II disease
- Prenatal testing for known familial mutation(s).
- Assessment of carrier status in high risk family members known mutation analysis
Clinical Sensitivity: In 3 unrelated Korean girls with type II mucolipidosis, compound heterozygosity for 5 different mutations was detected in the GNPTAB gene . In 6 patients with clinically and biochemically diagnosed mucolipidosis II, homozygosity or compound heterozygosity was identified for 7 mutations in the GNPTAB gene .
Analytical Sensitivity: ~99%
Prevalence: The estimated prevalence of all lysosomal storage disorders is 2-5 per 100,000. The prevalence of ML II is not specifically known, but is likely to be rare and may vary by ethnicity.
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.
- Known Mutation Analysis (KM) is available to test family members.
- Deletion/Duplication Assay is available separately for individuals where mutations are not identified by sequence analysis. Refer to the test requisition or contact the laboratory for more information.
- Prenatal testing is available for known familial mutations only. Please call the Laboratory Genetic Counselor for specific requirements for prenatal testing before collecting a fetal sample.