The purpose of this observational research study is to learn more about the natural history of fucosidosis, its symptoms, and how it develops over time.

This study intends to collect information from participants diagnosed with fucosidosis; however, this study does not include any medication or treatment other than the usual medical care provided to study participants.

The information collected in this study will be used to help understand the disease characteristics of fucosidosis; with this information potentially being able to help design future studies and treatments for this disease.

There is currently no approved treatment for patients with fucosidosis.

The study consists of 2 parts: a) Part A - retrospective data collection, and b) Part B - prospective data collection.

Time Perspective: Both retrospective (Part A) and prospective (Part B).

Enrollment: Part A is anticipated to enroll up to 57 participants for retrospective data collection. Part B is anticipated to enroll up to 31 participants for prospective data collection, the majority of whom are expected to be participants also enrolled in Part A.

Inclusion Criteria (Part A):

- Confirmed diagnosis of fucosidosis

Exclusion Criteria (Part A):

• Patient/parent/caregiver not willing to consent to participate
• Patient deceased with no availability of appropriate historical consent, and patient's family/caregivers are either unable to be contacted, or refuse consent to data sharing

Inclusion Criteria (Part B):

• Patient is alive
• Confirmed diagnosis of fucosidosis

Exclusion Criteria (Part B):

• Patient/parent/caregiver not willing to consent to participate
• Current participation in an interventional or therapeutic study
• Patients who, in the opinion of the site investigator, would be unable or unsuitable to participate in the demands of the study

Individuals of any age diagnosed with fucosidosis. Part A: living and deceased participants. Part B: living participants.