What is Fucosidosis?

Fucosidosis is one of the diseases classified as “lysosomal storage diseases*.”
Among the lysosomal storage diseases, fucosidosis is known to have a very small number of patients.
There are about a hundred or so cases worldwide, and only a few cases have been reported in Japan.

*Lysosomes are one of the intracellular organelles that work as one of the “waste processing factories” by using various enzymes to break down unnecessary substances in the body. Recently, lysosomes are considered to be involved a variety of cellular functions, not just waste disposal. With Lysosomal storage diseases, enzymes in the lysosomes do not function properly, causing an accumulation of unnecessary and a variety of symptoms. Currently, some 60 diseases have been identified, and 31 of them are registered as designated intractable diseases in Japan.

Patients with this disease have the gene mutation in the FUCA1 gene with the ability of α-L-fucosidase to perform its function correctly. The gene mutation in the FUCA1 causes an accumulation of complex sugar molecules in cells that eventually leads cells to malfunction.

Types of Fucosidosis

Fucosidosis is categorized as “Type I” or “Type II” according to age of onset and symptoms.

“Type I” is a severe form with rapid symptom progression characterized by elevated levels of sodium chloride (NaCl) in the sweat, occurring with psychomotor retardation during infancy from 3 months to 1.5 years of age, leading to immobilization.

“Type II” onsets at the age of 1 to 2 years and is characterized by angiokeratomas. It progresses relatively slowly, often into adulthood.

Symptoms

Symptoms and severity vary among patients, but the following symptoms are generally seen.

Diagnosis

If there is a possibility of fucosidosis, MRI and urinalysis will be performed.
Enzyme diagnosis and genetic testing using blood and skin cells are then performed to confirm the diagnosis.

Treatment

Supportive care is provided based on the symptoms, such as anti-epileptic medications for seizures.

Prognosis

The course of fucosidosis varies by the type of disease, with differences in symptoms even within families.
As symptoms progress, tube feeding or a ventilator may become necessary.

Editorial supervision: Norio Sakai, MD, PhD (Specially Appointed Professor, Developmental Child Health Science, Department of Children's and Women's Health, Division of Health Sciences, Osaka University Graduate School of Medicine)