The **RPL21P123** gene is a pseudogene located on chromosome 21. Pseudogenes are segments of DNA that resemble functional genes but are typically non-functional. RPL21P123 is a member of the ribosomal protein L21 family, specifically denoting it as a processed pseudogene derived from the RPL21 gene, which encodes ribosomal protein L21, an essential component of the ribosome involved in protein synthesis.

### Additional Details about RPL21P123:
1. **Associated Genes:**
   - The RPL21P123 as a pseudogene primarily relates to the RPL21 gene. RPL21 is part of the 60S ribosomal subunit, and its functionality in the ribosome could influence the expression and regulation of other ribosomal protein genes. Registered associations with other ribosomal protein genes (e.g., RPL21) due to their functional nature in protein translation are common, although specific genes may not be explicitly documented in public databases for this pseudogene.

2. **Aging or Age-Related Diseases:**
   - While no direct association with aging or specific age-related diseases has been established for RPL21P123 due to its status as a pseudogene, ribosomal proteins and their regulation have been implicated in the aging process and age-related conditions. Dysregulation of protein synthesis is a common feature in many age-related diseases such as neurodegeneration, cancer, and metabolic disorders. Therefore, while RPL21P123 may not have direct implications, its parent gene might.

3. **Drug Interactions:**
   - Currently, there is no specific information regarding direct drug interactions with the RPL21P123 pseudogene itself. However, drugs that target ribosomal function or protein synthesis (such as antibiotics like doxycycline and azithromycin) may indirectly affect the biological pathways in which ribosomal proteins like RPL21 and potentially RPL21P123 are involved. If new research emerges, this area might provide more insights into indirect associations.

4. **Pathways and Biological Processes:**
   - RPL21P123 itself may not have a defined pathway since it is a pseudogene; however, **RPL21**, from which it is derived, is involved in several important biological processes:
     - **Ribosome biogenesis**: Plays a crucial role in the formation of the ribosomal subunits.
     - **Protein synthesis**: Engages in the translational process as a structural part of the ribosome.
     - **Cellular response to stress**: The ribosomal proteins can also be involved in responses to cellular stress, influencing mechanisms such as apoptosis and cell cycle regulation.

In summary, while RPL21P123 itself does not exhibit significant biological functions associated with aging, diseases, or pharmacological interactions, its relation to the ribosomal protein family and the general implications of ribosomal activity suggest that ongoing research might reveal more details on its potential roles and connections.