Objective:

To report a case of fucosidosis associated with a novel homozygous pathogenic variant in the FUCA1 gene and to highlight the disorder's phenotypic heterogeneity, particularly in the absence of typical features such as hepatosplenomegaly.

Approach:

• Case Presentation: A male patient of Mexican descent was evaluated for developmental delays and neurological symptoms, with genetic analysis identifying a novel homozygous mutation in the FUCA1 gene.

Key Findings:

• The patient exhibited prominent neurological symptoms and atypical skin lesions without hepatosplenomegaly or cardiac involvement.
• A novel homozygous nonsense mutation, c.557 T > A (p.Leu186*), was identified in the FUCA1 gene.
• The case expands the known mutation spectrum of FUCA1 and highlights the disorder's phenotypic heterogeneity.

Interpretation:

The findings illustrate the clinical variability of fucosidosis and the necessity for genetic testing in atypical cases.

Limitations:

• The case study is based on a single patient, limiting generalizability.
• Whole-exome sequencing was not completed due to logistical issues related to patient access and resources.

Conclusion:

The case highlights the phenotypic diversity of fucosidosis and the critical role of early genetic diagnosis.