Overall, this analysis of SP-AbT in patients with PCD together with the assessment of CD19+ B-lymphocyte counts underlines the importance of at least 30 CD19+ cells/μL for sufficient vaccination response and helps to further characterize factors impacting SP-AbT formation in MM patients with the most important factors being older age, anti-CD38-directed treatment, poor remission status and quadruplet treatment as newly identified factors. The gene discussed is CD19; the disease is Miyoshi myopathy.