Acknowledgement of Galactosialidosis has not been added yet.

Galactosialidosis is extremely rare and the incidence and prevalence of the disorder is unknown. More than 100 cases have been reported in the medical literature. About 60% of the reported cases have been the juvenile/adult form. Most individuals with galactosialidosis have been found to be of Japanese descent.

Name	Abbreviation
Cathepsin A deficiency	None
Goldberg syndrome	None
lysosomal protective protein deficiency	None
neuraminidase deficiency with beta-galactosidase deficiency	None
protective protein/cathepsin A deficiency	None
PPCA deficiency	None

The cause of galactosialidosis is a mutation in the CTSA gene. This gene provides the instructions to produce an enzyme known as cathepsin A, which works with two other enzymes known as neuraminidase 1 and beta-galactosidase to break down certain sugars, proteins and fats within lysosomes. Cathepsin A forms a protein complex with these other two enzymes and protects them from breaking down too soon. A mutation in the CTSA gene results in ineffective or insufficient levels of cathepsin A, and, consequently, the other two enzymes cannot function properly or break down too soon.

Galactosialidosis is an autosomal recessive disorder, meaning that both parents must have a mutation in at least one of two genes associated with the disorder. Galactosialidosis can only be present if an individual has two copies of the mutation in the specific gene, one passed on from each parent.

There are three forms of galactosialidosis based on the age at which the symptoms develop.

The early infantile form appears with extensive swelling caused by fluid accumulation before birth (hydrops fetalis), an enlarged liver and spleen (hepatosplenomegaly), and a soft out-pouching of the lower abdomen (inguinal hernia). Other features include abnormal bone development, an enlarged heart, and distinctive facial features. Some individuals have psychomotor delays, an eye abnormality called a cherry-red spot and kidney impairment that ultimately can progress to kidney failure. Individuals with this form are typically diagnosed between birth and 3 months.

The late infantile form shares some of the symptoms of the early infantile form, however, the features are less severe and occur later in infancy. This form is characterized by short stature, cloudy of the corneas, abnormal bone development, heart valve problems, enlarged liver and spleen, and distinctive facial features. Rarely, this form also presents with psychomotor delay. This form usually develops within the first year of life.

The juvenile/adult form differs from the other two. This form is distinguished by difficulties in movement and coordination that can lead to frequent falls, involuntary muscle twitching, seizures and slowly progressive intellectual disability. Spinal abnormalities may develop. Individuals may also have clusters of dark red spots or discoloration on the skin (angiokeratomas), distinctive facial features, a cherry-red spot in the eyes and vision and hearing loss. The average age this form of galactosialidosis tends to develop is 16, but the exact age of onset can vary greatly.

A diagnosis for galactosialidosis is suspected when the characteristic features of the disorder, including the cherry-red spots in the eyes and distinctive facial features, are present.

A diagnostic tests can confirm the presence of mutations in the CTSA gene.

Further diagnosis of the form is based on the age at which the disorder appears.

Tests called enzyme assays can be used to measure the activity of the enzymes reduced in galactosialidosis: neuraminidase 1 and beta-galactosidase. Screening the urine may reveal increased levels of certain sugars called oligosaccharides.
A diagnosis can be confirmed through molecular genetic analysis by the identification of a mutation in the CTSA gene.

Currently, there is no cure for galactosialidosis. Treatment options are aimed at the various individual problems that the disorder presents. This may require the patient to have regular check-ups with their doctor and various specialists for each symptom.

The prognosis for galactosialidosis depends on when the symptoms begin to develop.  Severity and speed of progression increases the earlier the disorder occurs. The early infantile form is very severe and individuals diagnosed with this form typically only live to late infancy. The late infantile form has a variable life expectancy based on the severity of the symptoms. The juvenile/adult form is usually associated with a normal life span.

Genetic counseling is recommended for individuals and families affected by galactosialidosis. Psychosocial support is beneficial for the whole family as well.

Abaroa L, Garretto NS, Arakaki T, et al. Myoclonus and angiokeratomas in adult galactosialidosis. Mov Disord. 2011;26:756-757.

Caciotti A, Catarzi S, Tonin R, et al. Galactosialidosis: review and analysis of CTSA gene mutations. Orphanet J Rare Dis. 2013;8:114.

De Geest N, Bonten E, Mann L, et al. Systemic and neurologic abnormalities distinguish the lysosomal disorders sialidosis and galactosialidosis in mice. Hum Mol Genet. 2002;11(12):1455-1464.

Galactosialidosis. Genetic Home Reference website. http://ghr.nlm.nih.gov/condition/galactosialidosis 

Galactosialidosis; GSL. Online Mendelian Inheritance in Man (OMIM) website. http://www.omim.org/entry/256540