RGD uses the Human Disease Ontology (DO, https://disease-ontology.org/) for disease curation across species. RGD automatically downloads each new release of the ontology on a monthly basis. Some additional terms which are required for RGD's curation purposes but are not currently covered in the official version of DO have been added. As corresponding terms are added to DO, these custom terms are retired and the DO terms substituted in existing annotations and subsequently used for curation.
A myopathy that is characterized by childhood onset of progressive muscle weakness and atrophy primarily affecting the proximal muscles in males between 5 and 10 years old, has_material_basis_in mutation in the VMA21 gene on chromosome Xq28. (DO)