Danon disease is caused by loss of LAMP2 itself, rather than a glycosylation defect, but the observed LAMP2 underglycosylation in TMEM165-depleted cells (Foulquier et al., 2012) suggests an avenue by which TMEM165 dysfunction might indirectly affect lysosomal proteins relevant to cardiac pathology. This evidence concerns the gene LAMP2 and Danon disease.