Electron Microscopic Finding in Skin Biopsies from Patients with Danon Disease
J Alroy, R Pfannl, D Slavov, MRG Taylor. Tufts University School of Medicine, Boston, MA; Tufts Cumming's School of Veterinary Medicine, Grafton, MA; Tufts Medical Center, Boston, MA; University of Colorado, Aurora, CO
Background: Danon Disease is an X-linked lysosomal storage disease. It is due to primary deficiency of lysosomal-associated membrane protein-2 (LAMP-2). LAMP-2 is an important regulator of maturation of both autophagosomes and phagosomes. Deficiency of LAMP-2 results in accumulation of autophagosomes in multiple tissues and a phenotype triad of hypertrophic cardiomyopathy, myopathy, and mental retardation. A milder phenotype occurs in females. Clinical manifestation typically develops in boys in the first two decades of life. Skin biopsy is a useful cost effective tool for the diagnosis of other lysosomal storage diseases, but its role in Danon disease has not been studied.
Design: In this study we obtained skin biopsies from the forearms of a 24-years- old man and a 43-years-old woman and her 9-year-old son from two unrelated families. The diagnosis of Danon diseases was confirmed by DNA analysis and absent LAMP-2 protein in skin fibroblasts from both males. The 2-mm2 biopsies were fixed in Trump's fixative and postfixed in 1% osmium tetroxide in sodium cacodylate buffer, stained with 5% uranyl acetate, dehydrated and embedded in resin (Epon-812). Thick sections (1um) were stained with toluidine blue. Thin sections were cut at 50-70nm, stained with uranyl acetate and lead citrate, and photographed with a transmission electron microscope.
Results: Few large membrane bound electron lucent vacuoles, i.e., lysosomes were noted in myelinated axons and in some smooth muscle and fewer in perineural cells. Some fibroblasts contain both electron lucent lysosomes as well as lysosomes that contain electron dense material. Rare storage of lamellated membrane structures was noted in unmyelinated axons.
Conclusions: These unique morphological findings demonstrate the usefulness of skin biopsies in the diagnosis of Danon disease. They are distinct from those seen in patients with muscopolysaccharidosis, with glycolipids and oligosacchardide storage diseases, neuronal ceroid lipofuscinosis, as well as various myopathies.
Wednesday, March 24, 2010 9:30 AM
Poster Session V # 258, Wednesday Morning