Mucopolysaccharidosis IVa


MPS IVA Morquio disease (OMIM 253000) is an autosomal recessively inherited mucopolysaccharide storage disorder caused by a deficiency of the lysosomal enzyme N-acetylgalactosamine-6-sulphatase (GALNS, galactose-6-sulphate sulphatase) resulting in the accumulation of keratan sulphate and chondroitin-6-sulphate mainly in the cornea and cartilage, leading to distinguishing skeletal abnormalities. MPS IVA is a multisystemic disorder with clinical symptoms covering a wide spectrum of characteristics and is distinguished from other MPS by a spondyloepiphyseal dysplasia and normal intelligence. In the classical and most severe form, symptoms begin between 1-4 years of age and include tendency to fall, coarse features, dwarfism with short trunk, osteoporosis, corneal deposits, hearing impairment, and hepatomegaly. A milder form of MPS IVA is characterized by mild bone and somatic involvement with survival to 60 years of age and normal quality of life. The gene for GALNS is located on chromosome 16q24.3 and has 14 exons. The GALNS cDNA has an open reading frame of 1566 bp which encodes a 522 amino acid protein.

Referral information

This service is funded by the National Commissioning Group (NCG). Samples received from England, Northern Ireland and Scotland are charged to NCG with the majority of samples being received from The Willink Metabolic Unit. New patients are initially diagnosed by enzyme analysis, therefore patients will usually have already been referred to a relevant NCG centre before DNA analysis is requested. Funding from the NCG also covers carrier detection, by DNA analysis, for family members.

Price & reporting times

Test Price NHS (£) Price non- NHS (£ ) TRT (calendar days)
Mutation scanning POA POA 56
Single mutation test POA POA 28
Urgent/Predictive single mutation test POA POA 14

Test validation & quality assurance - information for users

The laboratory is UKAS assessed against ISO 15189 standards.

Sample requirements

4ml EDTA blood sample. If Willink laboratory testing is required, a 10ml urine sample is required

Referral guidelines

Please see our referral guidelines for more information.

OMIM Number(s) - 253000

Gene(s) - GALNS