Symptoms of Morquio syndrome include the excretion of specific urinary glycosaminoglycans and skeletal abnormalities. Most individuals affected by Morquio syndrome do not have coarse facial features or mental retardation. Skeletal manifestations of Morquio syndrome include: odontoid hypoplasia, a striking short trunk dwarfism, and genu valgus. Compared to other patients with MPS, those with Morquio syndrome tend to have greater spine involvement with scoliosis, kyphosis, and severe gibbus, as well as platyspondyly, rib flaring, pectus carinatum, and ligamentous laxity. In earlier clinical descriptions, MPS Type IVA was considered to have more severe manifestations than type IVB. However, with the ability to differentiate between types A and B by enzyme analysis, it is understood that significant variability in clinical expression exists within both groups. No clear clinical differentiation between Morquio syndrome type IVA and IVB exists.
Mutations to the GALNS gene cause deficiency of galactosamine-6-sulfatase. Diagnostic sequencing analysis of the GALNS gene coding region is available for MPS IV A 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 (LX).
For questions about testing for MPS IV A, call the Emory Genetics Laboratory at (404) 778-8499 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). Tomatsu S, Fukuda S, Cooper A, Wraith JE, Rezvi GMM, Yamagishi A, Yamada N, Kato Z, Isogai K, Sukegawa K, Kondo N, Suzuki Y, Shimozawa N, Orii T. Mucopolysaccharidosis IVA: identification of a common missense mutation I113F in the N-acetylgalactosamine-6-sulfate sulfatase gene. Am. J. Hum. Genet.57: 556-563, 1995.
2). Fukuda S, Tomatsu S, Masuno M, Ogawa T, Yamagishi A, Rezvi GMM, Sukegawa K, Shimozawa N, Suzuki Y, Kondo N, Imaizumi K, Kuroki Y, Okabe T, Orii T. Mucopolysaccharidosis IVA: submicroscopic deletion of 16q24.3 and a novel R386C mutation of N-acetylgalactosamine-6-sulfate sulfatase gene in a classical Morquio disease. Hum. Mutat. 7: 123-134, 1996.
3).Tomatsu, S.; Montano, A. M.; Nishioka, T.; Gutierrez, M. A.; Pena, O. M.; Trandafirescu, G. G.; Lopez, P.; Yamaguchi, S.; Noguchi, A.; Orii, T. Mutation and polymorphism spectrum of the GALNS gene in mucopolysaccharidosis IVA (Morquio A). Hum. Mutat. 26: 500-512, 2005.
- Confirmation of a clinical diagnosis of MPS IV A Disease
- Prenatal testing for known familial mutation(s).
- Assessment of carrier status in high risk family members known mutation analysis.
This assay does not interrogate the promoter region, deep intronic regions or other regulatory elements. Large deletions are not detected by this analysis. Results of molecular analysis must interpreted in the context of the patients clinical and/or biochemical phenotype.
Clinical Sensitivity: Tomatsu S, et al. reported a summary of 148 mutations found in affected patients (84% of alleles interrogated) 
Analytical Sensitivity: ~99%
Prevalence: The estimated prevalence of all lysosomal storage disorders is 2-5 per 100,000. The prevalence of MPS IV is not specifically known, but is likely to be rare and may vary by ethnicity. Results of molecular analysis must interpreted in the context of the patient's clinical and/or biochemical phenotype.
Submit only 1 of the following specimen types
Preferred specimen type: Whole Blood
Type: Whole Blood
Specimen Requirements:In EDTA (purple top) or ACD (yellow 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.
- Mucopolysaccharide screen (urine GAG) (GA)
- Known mutation analysis (Custom Diagnostics) is available to test family members.
- Deletion/duplication analysis for the GALNS gene is available separately for individuals where mutations are not identified by sequence analysis.
- 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.