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.
Four genetic disorders of keratinization are known to have a structural defect of tonofibrils. In the Curth-Macklin form of ichthyosis hystrix (IHCM), concentric unbroken shells of abnormal tonofilaments form around the nucleus. IHCM is caused by heterozygous mutation in the KRT1 gene (139350) on chromosome 12q13. (OMIM)