While in alpha‐mannosidosis, increased expression of LAMP‐1 was most pronounced in the CD4 and CD8 (T‐cell) compartment (Supplemental Figure S4), increased LAMP‐1 expression was especially profound in the CD20 (B‐cell) compartment of patients with sialidosis (Supplemental Figure S5). Here, CD4 is linked to sialidosis.