Galactosialidosis

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Obesity, Sleep & Internal medicine
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Galactosialidosis
Synonyms
Pronounce
Specialty	Medical genetics
Symptoms	Coarse facial features, cherry-red spot, myoclonus, ataxia, angiokeratoma, hepatosplenomegaly
Complications	N/A
Onset
Duration
Types
Causes	Genetic mutation in the CTSA gene
Risks
Diagnosis	Genetic testing, enzyme assay
Differential diagnosis	Sialidosis, GM1 gangliosidosis
Prevention
Treatment	Supportive care
Medication
Prognosis	Varies depending on type
Frequency	Rare
Deaths

Other Names: Goldberg syndrome; Neuraminidase deficiency with beta-galactosidase deficiency; Lysosomal protective protein deficiency of; Protective protein/Cathepsin A deficiency; Cathepsin A deficiency of; GSL; Neuraminidase/beta-galactosidase expression; PPCA deficiency.

Galactosialidosis affects many different body systems, including the brain, eyes, muscles, and skeleton.

Types

There are three different types: early infantile, late infantile and juvenile/adult. The most common type is juvenile/adult galactosialidosis.

Epidemiology

The prevalence of galactosialidosis is unknown; more than 100 cases have been reported. Approximately 60 percent of people with galactosialidosis have the juvenile/adult form. Most people with this type of the condition are of Japanese descent.

Cause

Mutations in the CTSA gene cause all forms of galactosialidosis. The CTSA gene provides instructions for making a protein called cathepsin A, which is active in cellular compartments called lysosomes. These compartments contain enzymes that digest and recycle materials when they are no longer needed. Cathepsin A works together with two enzymes, neuraminidase 1 and beta-galactosidase, to form a protein complex. This complex breaks down sugar molecules (oligosaccharides) attached to certain proteins (glycoproteins) or fats (glycolipids). Cathepsin A is also found on the cell surface, where it forms a complex with neuraminidase 1 and a protein called elastin binding protein. Elastin binding protein plays a role in the formation of elastic fibers, a component of the connective tissues that form the body's supportive framework.

CTSA mutations interfere with the normal function of cathepsin A. Most mutations disrupt the protein structure of cathepsin A, impairing its ability to form complexes with neuraminidase 1, beta-galactosidase, and elastin binding protein. As a result, these other enzymes are not functional, or they break down prematurely.

Galactosialidosis belongs to a large family of lysosomal storage disorders, each caused by the deficiency of a specific lysosomal enzyme or protein. In galactosialidosis, impaired functioning of cathepsin A and other enzymes causes certain substances to accumulate in the lysosomes.

Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Signs and symptoms

The following list includes the most common signs and symptoms in people with galactosialidosis. These features may be different from person to person, even between people with the same type. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom or feature that has been described in this condition. Infants with early infantile galactosialidosis have symptoms that usually appear before or at the time of birth. The signs and symptoms of include:

• Abnormal fluid build up in the fetus or newborn (hydrops fetalis)
• Enlarged liver and/or spleen (hepatosplenomegaly)
• Enlarged heart (cardiomyopathy)
• Abnormal bone development (dysostosis multiplex)
• Cherry red spot on the back of the eye
• Kidney disease that gets worse with time
• Facial features that are described as 'coarse'

Symptoms of the late infantile type of galactosialidosis usually start after 6 months of age, and are similar, but less severe, to those of the early infantile type. Additional features include hearing and vision loss, growth problems, and seizures. The juvenile/adult type of galactosialidosis has symptoms that are somewhat different than those of the other two types. Symptoms typically start in adolescence, but the age at onset and severity is variable. Symptoms include:

• Difficulty coordinating movements (ataxia)
• Muscle twitches (myoclonus)
• Seizures
• Visual loss
• Dark red spots on the skin (angiokeratomas)

The symptoms of the early and late infantile types of galactosialidosis often lead to a shortened life span. The symptoms of the juvenile/adult type vary in severity and age of onset. The symptoms include intellectual disability that gets worse with time, but lifespan is not generally affected.

Diagnosis

Galactosialidosis is diagnosed based on the symptoms, a clinical exam, and the results of genetic testing for variants in the CTSA gene. The type of galactosialidosis is determined by the age that symptoms begin.

Treatment

Treatment for galactosialidosis is focused on managing the symptoms. Specialists involved in the care of someone with galactosialidosis may include:

• Medical geneticist
• Neurologist
• Ophthalmologist

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NIH genetic and rare disease info

• NIH info on Galactosialidosis

Galactosialidosis is a rare disease.

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