DST-CMT is caused by autosomal recessive mutations in the DST gene. This type of CMT, that is, the underlying gene mutation that causes this type of CMT, was identified extremely recently, in 2020. There is only the published paper by Zuchner, Sherer et al., (2020) identifying the associated mutation in the DST gene that causes this type of CMT.
This type of CMT does not have a [number] [letter] name as the other types of CMT do. It is only referred to as DST-CMT at present time. This could very well change in the near future.
The mentioned paper: https://ng.neurology.org/content/6/5/e496
Article announcing the findings in the paper: https://www.pennmedicine.org/news/news-releases/2020/august/penn-researchers-identify-new-genetic-cause-of-a-form-of-inherited-neuropathy