Galactosialidosis

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Galactosialidosis is caused by a mutation (change) in the CTSA gene. This gene provides instructions to produce the enzyme called cathepsin A which works with two other enzymes (neuraminidase 1 and beta-galactosidase) to break down certain sugars, proteins and fats within lysosomes (an organelle that contains digestive enzymes).  

The enzyme Cathepsin A forms a protein complex together with the two other enzymes to protect them from breaking down too quickly. A mutation in the CTSA (like in patients with Galactosialidosis) leads to ineffective or insufficient levels of cathepsin A which results in the other two enzymes not being able to function properly or for them to break down too soon.  

The prevalence of galactosialidosis is currently unknown. More than 100 cases of the condition have been reported so far. An estimated 60% of people with the condition have the juvenile (adolescent)/adult form. Most people with this form of the condition are of a Japanese descent.   

There are three forms of galactosialidosis which are characterized by the age at which the symptoms start as well as the features themselves.  

 The early infantile form: 

•  hydrops fetalis (extensive swelling caused by fluid build-up before birth) 
• inguinal hernia (a soft outpouching in the lower abdomen) 
• hepatosplenomegaly (an enlarged liver or spleen)  
• dysostosis multiplex (abnormal bone development)  
• distinctive facial features often described as being “coarse” 
• cardiomegaly (enlarged heart) 
• cherry-red spot (eye abnormality)  
• kidney disease  

 Infants with the early infantile form are usually diagnosed between birth and 3 months old. Infants with this form usually live into late infancy.  

The late infantile form:  

This form shares some symptoms with the early infantile form however the signs and symptoms of this form are usually less severe and begin later in infancy.  

• Short stature (height considerably below average)  
• Heart valve problems  
• “coarse” facial features  
• Intellectual disability  
• Hearing loss 
• Cherry-red spot (eye condition) 

 Children with this form of the condition usually develop symptoms within the first year of their life. The life expectancy for children with this form can vary depending of how severe the symptoms are.  

 The juvenile/adult form: 

The symptoms in this form are quite different compared to the other two forms:  

•  Ataxia (difficulty coordinating movements)  
• Myoclonus (muscle twitches)  
• Seizures 
• Progressive intellectual disability  
• Angiokeratomas (dark red spots on the skin) 
• Abnormalities in the bones of the spine  
• “coarse” facial features  
• Cherry-red spot (eye condition) 
• Vision loss  
• Hearing loss 

The age at which symptoms begin to develop in the form of the condition can vary amongst different individuals, with the average age being 16. Patients with this form usually have a normal life expectancy.  

A diagnosis for galactosialidosis is first suspected when signs of the disorder become present, such as cherry-red spots in the eyes and distinctive “coarse” facial features. Specialised tests called enzyme assays can be used to measure the enzymes (neuraminidase 1 and beta-galactosidase) that are reduced in the case of galactosialidosis. A specialised urine test can also be used to show increased levels of certain sugars called oligosaccharides. 

A confirmation of the diagnosis can be done through molecular genetic analysis which will show a mutation in the CTSA gene in the case of galactosialidosis. 

Treatment for this condition is based on treating the specific symptoms the patient has. One example is taking certain medications to control seizures. Galactosialidosis patients are advised to see their genetic counsellors, neurological, ophthalmological (eye specialist) and other specialists regularly when symptoms develop and to keep symptoms under control.  

Galactosialidosis is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents.  

The pattern of inheritance of galactosialidosis is autosomal recessive. This means that carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with galactosialidosis are carriers.   

When both parents are carriers, the risk to the baby in each pregnancy is  

•  25% chance (1 in 4) of developing the condition  
•  50% chance (1 in 2) for the baby to be a carrier of the condition  
•  25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier  

 Genetic counselling can be requested to get a full explanation.  

References are available on request. Please contact us by phoning 0845 241 2173 or emailing contact@metabolicsupportuk.org [Resource Library No: GLY032].