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香港黏多醣症暨罕有遺傳病互助小組
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Mucopolysaccharidoses

Mucopolysaccharidoses, commonly referred to as MPS, are a group of rare genetic metabolic disorders, and are regarded as lysosomal storage disorders.

Normally, the body makes enzymes to break down materials for our cells. For people with MPS and related diseases, the missing or insufficient enzyme prevents that normal process for the sugar glycosaminoglycans (or mucopolysaccharides), so they become stored in almost every cell of the body. As a result, cells do not function properly and cause progressive damage to the person throughout the body, including the heart, bones, joints, respiratory system, and nervous system. While the disease is not immediately apparent at birth, signs and symptoms develop with age as more cells become damaged by the accumulation of cell deposits. Most patients usually do not live through their twenties.

Mucopolysaccharidoses exist in a total of seven types ---- MPS I, II, III, IV, VI, VII, IX --- and numerous subtypes. There are no type V and VIII. The seven types are subdivided to subtypes according to enzyme defect and symptoms shown by the body. Although each type of MPS is clinically different, most patients generally experience a period of normal development and then followed by a decline in physical and/or mental function.

Types
Disease Subtypes
Cause
Symptoms and Treatments
How Common (Incidence estimates)
Our members
MPS I From most severe to the mildest: Lack of the enzyme alpha-L-iduronidase

Both parents also carry the defective gene.

PDF PDF file

(MPS I therapy approval dates: Aldurazyme (laronidase) – Hong Kong: Mar 2008; FDA: 30 Apr 2003; EMEA: Jun 2003)

 
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* Hurler syndrome (MPS I-H) MPS I-H: about 1 per 100,000 births.
* Hurler-Scheie syndrome (MPS I-HS) MPS I-HS: about 1 per 115,000 births.
* Scheie syndrome (MPS I-S) MPS I-S: about 1 per 500,000 births.
MPS II
(Hunter syndrome)
From most severe to the mildest: Lack of the enzyme iduronate sulfatase

The defective gene was passed from the mother.

PDF PDF file

(MPS II therapy approval dates: Elaprase (idursulfase) – Hong Kong: Oct 2008; FDA: Jul 2006; EMEA: Jan 2007)

 
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* MPS II A MPS II A: Similar to Hurler syndrome but much milder 1 per 100,000 to 150,000 male births.
* MPS II B MPS II B: Less obvious and slower progression Onset usually at 2-4 years old.
MPS III
(Sanfilippo syndrome)
  Lack of the enzyme heparan sulphate

Both parents also carry the defective gene.

PDF PDF file About 1 per 24,000 to 70,000 births.
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MPS IV
(Morquio syndrome)
  Lack of the enzyme keratan sulphate

Both parents also carry the defective gene.

PDF PDF file
PDF What is Lysosomal Storage Disorders?

(MPS IV therapy approval dates: Naglazyme (Galsulfase) – FDA: May 2005; Europe: Jan 2006)

PDF MPS IV Therapy Information

About 1 per 200,000 births.
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MPS VI
(Maroteaux-Lamy syndrome)
  Lack of the enzyme dermantan

Both parents also carry the defective gene.

PDF PDF file About 1 per 215,000 births.
4
MPS VII
(Sly syndrome)
  Lack of the enzyme beta-glucuronidase PDF PDF file < 1 per 250,000 births
0
MPS IX
(Natowicz syndrome)
  Lack of the enzyme hyaluronidase   Only 1 reported case in the world
0
Number of MPS patients =27

Other Rare Diseases

 
Types
Cause
Symptoms and Treatments
How Common (Incidence Estimates)
No. of Patients in HK*
Mucolipidosis Lack of enzymes to break down carbohydrates and lipids Early onset may include rigid arms and shoulders, later on with carpal tunnel syndrome. Half of the patients have hearing impairment and a mild form of mental impairment.

PDF PDF file

About 2-3 per 100,000 births.
1
Fabry disease Lack of the enzyme alpha-galactosidase A Pain or strange feeling, sometimes even burning feeling, at the hands and feet during childhood or adolescence.

Dark purple skin colour at the lower abdomen, thigh, prostate or external sexual organ.

(FDA approval date: Fabrazyme – 3 Aug 2001)

Click here for details
 
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Gaucher's disease Deficiency of enzyme glucocerebrosidase (also known as acid β-glucosidase) Hepatosplenomegaly, sports regulatory function of the imbalance, small limbs, bone deformation, fracture easily

(FDA approval date: Cerezyme – 23 May 1994)

Click here for details
About 1 per 100,000 births.
1
Pompe disease
(Glycogen storage disease Type II)
Lack of acid maltase Ventricular fat or less rapid expansion of the heart, eventually causing obstruction to aortic flow, muscle weakness.

Death by around 2 years old

(FDA approval date: Myozyme – 28 Apr 2006)

Click here for details

About 1 per 40,000 births.
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Atypical Hemolytic Uremic Syndrome
 
  Atypical hemolytic uremic syndrome (aHUS) is an extremely rare, life-threatening, progressive disease that frequently has a genetic component. In most cases it is caused by chronic, uncontrolled activation of the complement system, a branch of the body’s immune system that destroys and removes foreign particles. The disease affects both children and adults and is characterized by systemic thrombotic microangiopathy (TMA), the formation of blood clots in small blood vessels throughout the body, which can lead to stroke, heart attack, kidney failure, and death.

Click here for details

Estimated: About 1 per 500,000 births (USA)
2
Multiple sclerosis Virus or inflammation affecting the immune system Neurological symptoms such as visual disorders, tremor, numbness, dizziness, weakness, leg stiffness. These may go away or sustain, or worsen over time.

More common in women.

Click here for details

About 2-5 per 100,000 births.
1
Phenylketouria (PKU) Lack of an enzyme to breakdown amino acids Infants abnormally drowsy, unusually light skin. Feeding difficulties. Severe mental retardation if no treatment

Click here for details

Varies greatly in regions and ethnicity
2
Sotos Syndrome
(Cerebral Gigantism)
Mutation in a gene Excessive growth before and after birth, abnormally prominent forehead, and developmental delays in most children

Click here for details

About 1 per 14,000 births.
0
Hereditary epidermolysis bullosa Mutation in the keratin gene Recurring painful blisters and open sores, often after minor trauma, due to unusually fragile nature of the skin

Click here for details
About 1 per 50,000 births.
1
Urea cycle disorder Lack of an enzyme in the urea cycle to remove ammonia from the blood stream Amine caused by high blood coma, vomiting

Click here for details
About 1 per 10,000 births
1
Glutaric aciduria Type I Lack of an enzyme Neurological symptoms such as muscle stiffness, hand-foot-progressive chorea, paralysis, corner arch anti-sheets, legs turned out, the body was arcuate and so on, may have epilepsy, or sleeping with acute onset of coma

Click here for details
 
1
Interstitial deletion of chromosome 3q23 to 3q25      

 

1
Glycogen storage disease Lack of enzymes to breakdown glycogen Drowsiness, trembling, slow growth, increased abdominal circumference, fat accumulation in the cheek into a rounded doll-like. Nosebleeds or ears to inflammation, gingivitis, sores symptoms. After the emergence of rickets, anemia symptoms. Gland tumor complications such as liver, progressive renal failure, kidney stones, gout, anemia, osteoporosis, etc. About 1 per 10,000 births.
1
Williams Syndrome
 
Williams syndrome, also known as Williams–Beuren syndrome, is a rare neurodevelopmental disorder characterized by: a distinctive, "elfin" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; developmental delay coupled with strong language skills; and cardiovascular problems, such as supravalvular aortic stenosis and transient high blood calcium.

Click here for details
About 1 per 20,000 births
1
Huntington's Disease
 
Huntington's Disease is a rare inherited brain disorder caused by a mutation of a specific gene on chromosome 4. Since the most obvious symptoms of Huntington's Disease are abnormal involuntary body movements, it is often simply referred to as chorea.

Huntington's Disease, however, is not as simple as it seems. Chorea which typically causes an unsteady gait is only one of the first symptoms of the disease. Other accompanying symptoms include swallowing and speech difficulties. As the disease progresses, it also affects a number of mental and cognitive abilities, as well as certain aspects of personality.


Huntington's Disease patients usually develop symptoms after mid-adult life. In the later stage of the disease, eating, speech and mobility are extremely difficult if not impossible, and they may eventually become bedridden, facing an increased risk of infection.


Each child of a person with Huntington's Disease has a 50% chance of inheriting the gene. It is devastating not only to the patients but also to their families.


There is, at present, no cure for Huntington's Disease, but treatments are available to slow down the symptoms and help the patients function for as long and as comfortably as possible. The care and support of family and friends is profoundly critical to Huntington's Disease patients.

Affects 1 out of 1,000,000 in people of Asian descent.
1
WAGR Syndrome
 
WAGR syndrome is a rare genetic syndrome in which affected children are predisposed to develop Wilms tumour (a tumour of the kidneys), Aniridia (absence of the coloured part of the eye, the iris), Genitourinary anomalies, and Retardation. The G is sometimes instead given as "gonadoblastoma," since the genitourinary anomalies are tumours of the gonads (testes or ovaries).

Click here for details
Aniridia: 1/40,000 ~1:100,000
1
Prader-Willi Syndrome
 
Prader–Willi syndrome is a rare genetic disorder in which 7 genes (or some subset thereof) on chromosome 15 (q 11–13) are deleted or unexpressed (chromosome 15q partial deletion) on the paternal chromosome. Characteristic of PWS is "low muscle tone, short stature, incomplete sexual development, cognitive disabilities, problem behaviors, and a chronic feeling of hunger that can lead to excessive eating and life-threatening obesity."

Click here for details
1:12,000-15,000
1
Kabuki Syndrome
Kabuki syndrome is a rare genetic syndrome. Current statistics indicate somewhere between 1 and 10,000 and 1 in 32,000 people have Kabuki syndrome. "Genetic" means the individual is born with a condition and the cause of that condition resides in his or her genetic makeup. Genetic disorders can be passed down from one generation to the next (like Muscular Dystrophy) or could be a spontaneous genetic mutation caused by an error in DNAi replication. Genetic disorders like Down syndrome can occur with abnormalities at the chromosomal level, whereas other syndromes, like Kabuki syndrome, reside at the specific gene level.

Reference: http://www.kabukisyndrome.com/

1/32,000 (Japan)
1
Osteogenesis Imperfecta
People with Osteogenesis Imperfecta are born with defective connective tissue, or without the ability to make it, usually because of a deficiency of type I collagen.

8 types of OI can be distinguished. Most cases are caused by mutations in the COL1A1 and COL1A2 genes.

Click here for details
About 1 per 20,000 live births (USA)
1
Leigh Disease
. Leigh syndrome is a severe neurological disorder that typically arises in the first year of life. This condition is characterized by progressive loss of mental and movement abilities (psychomotor regression) and typically results in death within a couple of years, usually due to respiratory failure. A small number of individuals develop symptoms in adulthood or have symptoms that worsen more slowly

Click here for details
At least 1 in 40,000 newborns

0
Spinocerebellar Atrophy Type 35 and Spondyloepiphyseal Dysplasia
 
  .

 

1
Unknown
 
CTNNB1 gene mutation PDF Click here for details

 

1
Leber's hereditary optic neuropathy
 
Usually due to one of three pathogenic mitochondrial DNA (mtDNA) point mutations. These mutations are at nucleotide positions 11778 G to A, 3460 G to A and 14484 T to C, respectively in the ND4, ND1 and ND6 subunit genes of complex I of the oxidative phosphorylation chain in mitochondria. A mitochondrially inherited (transmitted from mother to offspring) degeneration of retinal ganglion cells (RGCs) and their axons that leads to an acute or subacute loss of central vision; this affects predominantly young adult males. LHON is only transmitted through the mother, as it is primarily due to mutations in the mitochondrial (not nuclear) genome, and only the egg contributes mitochondria to the embryo. Men cannot pass on the disease to their offspring.

 

1
Congenital Central Hypoventilation Syndrome, CCHS
The underlying cause of CCHS is mutation in the PHOX2B gene. Congenital central hypoventilation syndrome (CCHS) is a rare lifelong and life-threatening disorder. CCHS affects the central and autonomic nervous system which controls many of the automatic functions in the body such as heart rate, blood pressure, sensing of oxygen and carbon dioxide levels in the blood, temperature, bowel and bladder control, and more. The most recognized symptom of CCHS is the inability to control breathing that varies in severity, resulting in the need for life-long ventilatory support during sleep in some patients or all the time in others. There are estimated to be 1000 – 1200 cases of CCHS world-wide. CCHS affects males and females equally. Currently, there is no cure for CCHS.

Click here for details

1 in 200,000 newborns
1
Multiple Epiphyseal Dysplasia
Multiple epiphyseal dysplasia is a disorder of cartilage and bone development primarily affecting the ends of the long bones in the arms and legs (epiphyses). The majority of individuals are diagnosed during childhood; however, some mild cases may not be diagnosed until adulthood. There are two types of multiple epiphyseal dysplasia, which can be distinguished by their pattern of inheritance. Both the dominant and recessive types have relatively mild signs and symptoms, including joint pain that most commonly affects the hips and knees, early-onset arthritis, and a waddling walk. Although some people with multiple epiphyseal dysplasia have mild short stature as adults, most are of normal height.

Recessive multiple epiphyseal dysplasia is distinguished from the dominant type by malformations of the hands, feet, and knees and abnormal curvature of the spine (scoliosis). About 50 percent of individuals with recessive multiple epiphyseal dysplasia are born with at least one abnormal feature, including an inward- and upward-turning foot (clubfoot), an opening in the roof of the mouth (cleft palate), an unusual curving of the fingers or toes (clinodactyly), or ear swelling. An abnormality of the kneecap called a double-layered patella is also relatively common.

Click here for details

The incidence of dominant multiple epiphyseal dysplasia is estimated to be at least 1 in 10,000 newborns. The incidence of recessive multiple epiphyseal dysplasia is unknown. Both forms of this disorder may actually be more common because some people with mild symptoms are never diagnosed.
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Number of patients with rare diseases =33
Total Number of MPS + Rare Diseases Patients =60

* Note: Patient figures according to the number of patients who contacted our organization.
For information about other organizations and treatments for rare genetic diseases, please click here.

Updated: 6 November 2017

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