Vacuolated PAS‐positive lymphocytes as an hallmark of Pompe disease and other myopathies related to impaired autophagy

Abstract

Autosomal recessive Pompe disease is a lysosomal disorder caused by mutations of the acid-α-glucosidase (GAA) gene. Deficiency of GAA enzyme leads to glycogen accumulation and autophagy impairment in cardiac and skeletal muscles, but also in lymphocytes. Since an effective therapy is available, a rapid, sensitive, and specific test is crucial to early identify affected subjects. Number of lymphocytes containing PAS-positive vacuoles was evaluated on blood films from 72 consecutive adult patients with hyperckemia and/or muscle weakness, 13 genetically confirmed late-onset-Pompe-disease (LOPD) and 13 of their offspring. GAA activity, measured on dried blood spot (DBS) in all patients inversely correlated with number of PAS-positive lymphocytes. More than 4 PAS-positive lymphocytes were found in 11 out of the 72 patients (6 new diagnosis of LOPD, 3 different glycogen storage myopathies, 1 glucose-6-phosphate dehydrogenase deficiency, 1 caveolinopathy), in all 13 LOPD patients and in the 13 LOPD offspring. These latter resulted to have all a single GAA mutation but low GAA levels. Immunostaining with the autophagy markers LC3 and p62 confirmed the autophagic nature of lymphocytes vacuoles. ROC curve assessment of PAS-positive lymphocytes disclosed 100% of sensitivity and 94% of specificity in recognizing both compound heterozygous and heterozygous GAA carriers. The other myopathies with more than 4 PAS-positive lymphocytes appeared to be all related to impaired autophagy, which seems to be responsible of PAS-positive vacuolated lymphocytes formation. Quantification of PAS-positive lymphocytes in blood films is useful to identify autophagic vacuolar myopathies and should be routinely used as first level test for Pompe disease.

Mechanisms of Mitochondrial Dysfunction in Lysosomal Storage Disorders: A Review

“…Pompe disease (PD, glycogen storage disease type II) (OMIM #232300) is an autosomal recessive condition caused by mutations in the acid-α-glucosidase (GAA) gene. Deficiency of GAA enzyme leads to glycogen accumulation and an impairment of autophagy predominantly in skeletal and cardiac muscle [27].…”

Assessment of adeno-associated virus gene therapies efficacy on acid alpha-glucosidase restoration and glycogen storage correction in cardiac muscle of Pompe disease mice using synchrotron infrared and ultraviolet microspectroscopies

“…These biomarkers are routinely analysed by performing biochemical assays and histopathological investigations consisting of glycogen PAS staining and GAA immunohistochemistry on tissue sections. 15,26,[55][56][57] Glycogen PAS staining is based on the principle of periodic acidinduced oxidative cleavage of carbon-to-carbon bounds in 1,2-glycols to form dialdehydes reacting with fuchsinsulphurous acid, which in turn combines with the basic pararosaline, yielding a magenta-like stain. 58 PAS staining could be used to quantify glycogen in tissue sections but the thickness of the sections has to remain constant to ensure the validity of the comparison of glycogen content between sections.…”

Vacuolated PAS-Positive Lymphocytes on Blood Smear: An Easy Screening Tool and a Possible Biomarker for Monitoring Therapeutic Responses in Late Onset Pompe Disease (LOPD)

“…In 2010, Hagemans et al collected peripheral blood films from patients with Pompe disease and controls showing that PAS-positive lymphocytes were more common in Pompe disease compared to controls and suggesting their possible role as diagnostic screening procedure ( 23 ). More recently Pascarella et al suggested that quantification of PAS-positive lymphocytes in blood films is useful to identify autophagic vacuolar myopathies and should be routinely used for Pompe disease diagnosis ( 25 ).…”