Morquio Syndrome A (MPS IVA): N-Acetylgalactosamine-6-Sulfatase Enzyme Analysis

Clinical Information

Morquio syndrome is characterized by short stature and trunk, large head, mildly coarse facies, widely spaced teeth, corneal clouding, a bell-shaped chest, vertebral anomalies, joint stiffness and kyphoscoliosis. Other features may include inguinal hernia, hepatomegaly and hearing loss. There is a wide spectrum of those affected ranging from mild to severe. There is typically no cognitive impairment.

Technical Information

N-acetylgalactosamine-6-sulfatase enzyme activity is measured using a 4-methylumbelliferyl (4-MU) substrate (leukocytes, fibroblasts) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) (DBS).

Specimen Requirements

• Accepted sample types for this test include dried blood spots (DBS), fibroblasts, and leukocytes.
• DBS: Approximately 75 uL of blood should be applied to each of the five circles on filter paper dried blood spot card. Allow blood to dry for at least 4 hours before shipping.
• Fibroblasts: Tissue sample should be stored in sterile culture media; cultured fibroblasts should be sent in two T25 flasks. Do NOT place tissue in formalin or formaldehyde. Do not freeze tissue.
• Leukocytes: A minimum of 5 mL whole blood (7-10 mL preferred) collected in a sodium heparin.

Transport Instructions

• DBS: Ship DBS card at ambient temperature.
• Fibroblasts: Ship tissue sample or cultured fibroblasts at ambient temperature
• Leukocytes: Whole blood should be shipped at ambient temperature. If leukocytes are being isolated at another laboratory, the pellet should be frozen after specimen processing and shipped frozen on dry ice.