GFAP mutations, age at onset, and clinical subtypes in Alexander disease

Area of Science:

• Neuroscience
• Genetics
• Rare Diseases

Background:

• Alexander disease (AxD) is a rare astrogliopathy characterized by leukodystrophy on MRI.
• AxD is caused by mutations in the glial fibrillary acidic protein (GFAP) gene.
• Understanding AxD phenotypes and their correlation with genetic factors is crucial for diagnosis and management.

Purpose of the Study:

• To characterize Alexander disease (AxD) phenotypes.
• To determine correlations between age at onset (AAO) and GFAP genetic mutations.
• To statistically define AxD subtypes based on clinical and genetic data.

Main Methods:

• Analysis of 30 new and 185 previously reported AxD cases.
• Statistical methods including Wilcoxon rank sum tests, survival analysis, and chi-squared tests.
• Latent class analysis (LCA) to identify distinct AxD patient groups.

Main Results:

• LCA identified two AxD classes: Type I (early onset, severe symptoms) and Type II (later onset, distinct neurological features).
• Type I AxD showed a significantly higher mortality risk compared to Type II.
• Specific GFAP mutations (R79, R239) were common and correlated with distinct clinical outcomes, with R239 associated with a more aggressive disease course.

Conclusions:

• Age at onset and GFAP mutation site are key predictors of AxD phenotype and prognosis.
• The study proposes revised AxD subtypes (Type I and Type II) based on statistically defined patient groups.
• These findings enhance the understanding of AxD heterogeneity and guide clinical management.