Morquio disease, or mucopolysaccharidosis type IV (MPS IV), is a rare disease with a genetic background belonging to the group of mucopolysaccharidoses. The cause of Morquio's disease is a deficiency of enzymes that break down mucopolysaccharides, the accumulation of which in the cell is responsible for the characteristic symptoms of the disease.
Contents:
- Morquio disease - causes
- Morquio disease - symptoms
- Morquio disease - diagnosis
- Morquio disease - treatment and enzyme replacement therapy
Morquio diseaseis a rare, lysosomal storage disease of genetic origin. It belongs to the group of mucopolysaccharidoses (MPS), hence its other name ismucopolysaccharidosis type IV (MPS IV) .
Morquio's disease was first described in 1929 by two doctors simultaneously, the Uruguayan pediatrician Luis Morquio and James Frederick Brailsford of Birmingham, England. This is why the disease is sometimes referred to as Morquio-Brailsford disease.
The prevalence of Morquio's disease selection has been estimated to be approximately 1 in 76,000 to 640,000 live births. The disease affects women as often as men.
Morquio disease - causes
The cause of Morquio's disease is an autosomal recessive genetic mutation. Which means that only one defective copy of a gene is enough to cause disease (we always have two copies of one gene in our body). Depending on the mutated gene, we distinguish:
- Morquio syndrome type A (MPS IV A)caused by mutation in the GALNS gene encoding galactosamine 6-sulfatase; this type of syndrome has a more severe clinical course
- Morquio syndrome type B (MPS IV B)caused by mutation in the GLB1 gene encoding beta-galactosidase; this type of syndrome has a milder clinical course
The consequence of genetic mutations is the deficiency of lysosomal enzymes in the cell, which are involved in the breakdown of glycosaminoglycans, e.g. dermatan sulfate, heparan sulfate, keratan sulfate.
Glycosaminoglycans are produced, broken down and eliminated from the body over a continuous cycle. In people with Morquio disease, as a result of an enzymatic block, undegraded glycosaminoglycans accumulate in the cells.
This causes functional disorders and symptomsdiseases in many different organs. Glycosaminoglycans play a special role in building bones, cartilage and tendons.
Morquio disease - symptoms
The first symptoms of Morquio's disease develop between the ages of 1 and 3. Therefore, usually no symptoms of the disease are observed in newborns. The most characteristic symptom of Morquio's disease is osteochondrodysplasia (disorders of bone and cartilage development), which is manifested by:
- growth inhibition and short stature
- lumbar hump
- cervical spine instability
- kyphoscoliosis with chest deformity
- abnormal development of epiphyses of long bones
- hip, knee, ankle and wrist dysplasia
- valgus knees
- flat feet
- loose joints
Changes to bone and cartilage are also accompanied by other disorders:
- valvular heart disease
- respiratory diseases
- hearing loss
- corneal opacity, retinal degeneration, glaucoma
- dental abnormalities (teeth are widely spaced and the enamel is grayish)
- impaired physical endurance
It is worth mentioning that Morquio's disease, unlike other types of mucopolysaccharidosis, does not cause mental retardation.
Morquio disease - diagnosis
The diagnosis of Morquio's disease is made on the basis of the patient's clinical picture in conjunction with the results of laboratory tests as:
- quantification of glycosaminoglycans in urine (e.g. keratan sulphate)
- in people with high urinary glycosaminoglycans, the enzymatic activity of 6-galactosamine sulfatase (MPS IVA diagnostics) or beta-galactosidase (MPS IVB diagnostics) in cell culture is assessed
- genetic tests to detect mutations of GALNS and GLB1 genes
It is also possible to diagnose Morquio's disease in the prenatal period.
Morquio disease - treatment and enzyme replacement therapy
Treatment of Morquio's disease is primarily symptomatic. Due to dysfunction of the locomotor system, people with Morquio's disease receive physical therapy, which is necessary to improve the quality of life of patients.
It is now possible to treat type A Morquio's disease with enzyme replacement therapy. In 2014, the US Food and Drug Administration (FDA) approved a drug called Vimizim, which contains the purified enzyme elosulfase alfa. The therapy consists of intravenous administration of a drug that replaces the lysosomal enzyme missing from the cell.
In Poland, the drug is waiting for reimbursement.
About the author
Karolina Karabin, MD, PhD, molecular biologist, laboratory diagnostician, Cambridge Diagnostics Polska A biologist by profession, specializing in microbiology, and a laboratory diagnostician with over 10 years of experience in laboratory work. A graduate of the College of Molecular Medicine and a member of the Polish Society of Human Genetics. Head of research grants at the Laboratory of Molecular Diagnostics at the Department of Hematology, Oncology and Internal Diseases of the Medical University of Warsaw. She defended the title of doctor of medical sciences in the field of medical biology at the 1st Faculty of Medicine of the Medical University of Warsaw. Author of many scientific and popular science works in the field of laboratory diagnostics, molecular biology and nutrition. On a daily basis, as a specialist in the field of laboratory diagnostics, he runs the content department at Cambridge Diagnostics Polska and cooperates with a team of nutritionists at the CD Dietary Clinic. He shares his practical knowledge on diagnostics and diet therapy of diseases with specialists at conferences, training sessions, and in magazines and websites. She is particularly interested in the influence of modern lifestyle on molecular processes in the body.
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