This booklet was written by Professor Dr Francois Eyskens of the PCMA vzw, the metabolic laboratory, and the Center of Inherited Metabolic Diseases at the University of Antwerp, Belgium. It focuses on the understanding, diagnosis and treatment of young people with the rare diseases, MPS (or mucopolysaccharidoses), as well as looking into the various types of Gaucher disease, a lysosomal storage disorder.
What are mucopolysaccharidoses?
MPS, or mucopolysaccharidoses (lysomal storage disorders), are multisystem disorders that show a broad clinical spectrum and a slow to fast clinical progression. MPS are autosomal recessive or X-linked recessive (MPS II) inherited disorders caused by a deficiency of a specific lysosomal enzyme, characterised by the accumulation of incompletely degraded glycosaminoglycans (GAGs) in connective tissue cells, leading to widespread organ dysfunction.
Why is it difficult to diagnose rare diseases?
The disease spectrum is broad and given that most physicians are not aware of the existence of these rare diseases, the diagnosis is significantly delayed in most patients. Among the more attenuated or milder subtypes (delay of proper diagnosis between 4-53 years after appearance of first clinical symptoms and signs) especially, misdiagnosis is common.
How cost-effective would early detection be?
In most of the rare disease cases, the earlier detection and treatment starts grants lower costs and better quality of life, in respect to those who are diagnosed in a late disease stage. As the cost of treating rare diseases accounts for a comparatively high percentage of national healthcare expenditure, improving the early diagnosis of lysosomal storage diseases like MPS would have a highly positive cost-saving impact.
What are the three types of Gaucher disease?
Gaucher disease affects around one in every 100,000 live births and is categorised into three subtypes depending on presence:
- Type 1 – Also known as non-neuronopathic Gaucher disease, this doesn’t affect the central nervous system and boasts symptoms that can appear any time during childhood or adulthood;
- Type 2 – Also known as acute neuronopathic Gaucher disease, this is a rapidly progressive form of the condition that affects newborns and infants. Characterised by severe neurological symptoms in the first year of life, including lockjaw, crossed eyes, hypertonia and difficulty swallowing, ost children with Type 2 Gaucher diseases don’t survive past the age of two; and
- Type 3 – Also known as neuronopathic Gaucher disease, this is similarly characterised by neurological symptoms; however, these are less severe and progress more slowly than in Type 2. Common symptoms include ataxia, myoclonic seizures and conjugate gaze palsies. People with Type 3 Gaucher disease can survive into their teens, 20s and even 50s.