Autophagic Vacuolar Myopathy Research Articles

Danon disease caused by two novel mutations of the LAMP2 gene: implications for two ends of the clinical spectrum

Danon disease is caused by mutations of the lysosome-associated membrane protein-2 (LAMP2) gene at Xq24. Male patients usually manifested as severe cardiomyopathy, mild myopathy and mental retardation. We describe two patients: the first patient presented with severe hypertrophic cardiomyopathy, Wolff-Parkinson-White syndrome, proximal muscle weakness, and chronic painless diarrhea; the second patient manifested as limb-girdle muscle weakness, mild left ventricular diastolic dysfunction, sub-clinical neuropathy. Muscle biopsies indicated autophagic vacuolar myopathy. Immunologic analysis demonstrated absence of the LAMP2 protein in the first patient, while a smear of expression was detected in the second patient. Two nonsense mutations (p.E298X and p. K402X) were identified in the two cases, respectively located in exon 7 and exon 9B of the LAMP2 gene. Our findings indicated that patients with Danon disease caused by mutations in exon 1 – 8 manifested as a typically severe phenotype, while patients with mutations in exon 9 of the LAMP2B isoform presented with a relatively benign phenotype.

Clinical Utility of LC3 and p62 Immunohistochemistry in Diagnosis of Drug-Induced Autophagic Vacuolar Myopathies: A Case-Control Study

BackgroundSome patients treated with chloroquine, hydroxychloroquine, or colchicine develop autophagic vacuolar myopathy, the diagnosis of which currently requires electron microscopy. The goal of the current study was to develop an immunohistochemical diagnostic marker for this pathologic entity.MethodologyMicrotubule-associated protein light chain 3 (LC3) has emerged as a robust marker of autophagosomes. LC3 binds p62/SQSTM1, an adapter protein that is selectively degraded via autophagy. In this study, we evaluated the utility of immunohistochemical stains for LC3 and p62 as diagnostic markers of drug-induced autophagic vacuolar myopathy. The staining was performed on archival muscle biopsy material, with subject assignment to normal control, drug-treated control, and autophagic myopathy groups based on history of drug use and morphologic criteria.Principal FindingsIn all drug-treated subjects, but not in normal controls, LC3 and p62 showed punctate staining characteristic of autophagosome buildup. In the autophagic myopathy subjects, puncta were coarser and tended to coalesce into linear structures aligned with the longitudinal axis of the fiber, often in the vicinity of vacuoles. The percentage of LC3- and p62-positive fibers was significantly higher in the autophagic myopathy group compared to either the normal control (p<0.001) or the drug-treated control group (p<0.05). With the diagnostic threshold set between 8% and 15% positive fibers (depending on the desired level of sensitivity and specificity), immunohistochemical staining for either LC3 or p62 could be used to identify subjects with autophagic vacuolar myopathy within the drug-treated subject group (p≤0.001).SignificanceImmunohistochemistry for LC3 and p62 can facilitate tissue-based diagnosis of drug-induced autophagic vacuolar myopathies. By limiting the need for electron microscopy (a time consuming and costly technique with high specificity, but low sensitivity), clinical use of these markers will improve the speed and accuracy of diagnosis, resulting in significantly improved clinical care.

P3.50 Autophagic vacuolar myopathy in a girl

Autophagic vacuolar myopathies (AVM) are defined as a group of diseases sharing an important morphological hallmark which is the occurrence of autophagic vacuoles. A subgroup of AVM is characterized by the sarcolemmal features of its autophagic vacuoles (AVSF). Based on this classification, several diseases with different etiologies, phenotypes and morphologies are related including acid maltase deficiency, Danon disease, infantile autophagic vacuolar myopathy and X-linked myopathy with excessive autophagy (XMEA).

自己貪食空胞性ミオパチーの病態解明と治療法開発

Autophagic vacuolar myopathy (AVM) is an entity defined by the presence of autophagic vacuoles on muscle pathology. There are two emerging categories in AVM in addition to the best characterized Pompe disease. One is Danon disease and its related disorders, which are characterized by autophagic vacuoles with unique sarcolemmal features (AVSF). AVSF express virtually all sarcolemmal proteins, in addition to acetylcholinesterase, on their vacuolar membranes. Danon disease is caused by primary deficiency of a lysosomal membrane protein, LAMP-2. Interestingly, in this disease, the number of AVSF increases as the patients age. Other AVSF myopathies include X-linked myopathy with excessive autophagy which is now known to be caused by VMA21 mutations. The other AVM is typified by the presence of rimmed vacuoles, which are actually clusters of autophagic vacuoles on electron microscopy. One of the well known diseases in this group is distal myopathy with rimmed vacuoles (DMRV), also called hereditary inclusion body myopathy (HIBM). DMRV is caused by mutations in GNE gene that encode a rate-limiting enzyme in the sialic acid biosynthetic pathway. Interestingly, in DMRV model mice, sialic acid supplementation almost completely precluded the disease phenotype, indicating that decreased sialic acid is the cause of myopathic phenotype and sialic acid supplementation can prevent the disease process. Interestingly, both genetically diagnosable AVSF myopathies are primarily due to lysosomal dysfunctions. In contrast, rimmed vacuoles are secondarily caused by extra-lysosomal defects, such as hyposialylation in DMRV/HIBM, and are formed at later stages of the disease.

Food for thought: autophagic vacuolar myopathies

Most paediatricians are familiar with the terms lysosomal storage disorders (LSDs) and neuromuscular disorders (NMDs), and these disease entities seem to have little in common. Here, I am giving a...

Danon disease: Case report and detection of new mutation

Danon disease is an X-linked disorder resulting from mutations in the lysosome-associated membrane protein-2 (LAMP2) gene. We report a male patient with skeletal myopathy, mental retardation, and massive hypertrophic obstructive cardiomyopathy necessitating heart transplantation. Immunohistochemistry of skeletal muscle and leukocytes, western blot analysis of leukocytes and cardiac muscle, flow cytometry, and DNA sequencing were performed. Muscle biopsy revealed autophagic vacuolar myopathy and lack of immunohistochemically detectable LAMP-2. Diagnosis of Danon disease was confirmed by western blot analysis of myocardial tissue and peripheral blood sample of the patient showing deficiency of LAMP-2 in myocardium and leukocytes. Moreover, absence of LAMP-2 in lymphocytes, monocytes and granulocytes was shown by flow cytometric analysis. Genetic analysis of the LAMP2 gene revealed a novel 1-bp deletion at position 179 (c.179delC) at the 3' end of exon 2, resulting in a frameshift with a premature stop codon.

An Autophagic Vacuolar Myopathy-Like Disorder Presenting as Nonimmune Hydrops in a Female Fetus

A 37-year-old woman presented for routine obstetrical care at 15 weeks' gestational age and the fetus was found to have hydrops fetalis. Following elective termination of the pregnancy at 18 weeks' gestational age, pathologic examination of the female conceptus revealed findings suggestive of a lysosomal storage disease within the liver and cardiac muscle. Enzyme assays for beta-galactosidase, neuraminidase, alpha-l-iduronidase, beta-glucuronidase, beta-glucosidase, Morquio disease type A enzyme, beta-fucosidase, alpha-mannosidase, and beta-mannosidase were all normal, ruling out many of the common storage diseases. Electron microscopy identified vacuoles within hepatocytes, Kupffer cells, and cardiac myocytes resembling the autophagic vacuoles characteristic of a group of diseases known as the autophagic vacuolar myopathies (AVMs). Because these diseases are exceptionally rare in females, and because such autophagic vacuoles have never before been described in liver, we propose a novel entity of "AVM-like lysosomal storage disease" presenting as nonimmune hydrops in a female fetus.

G.P.9.09 Autophagic vacuolar myopathy in a female patient

G.P.9.09 Autophagic vacuolar myopathy in a female patient

Danon Disease as a Cause of Autophagic Vacuolar Myopathy

Danon disease, an extremely rare X-linked dominant disorder, is characterized clinically by hypertrophic cardiomyopathy (HCM), skeletal myopathy, and variable degree of mental retardation with autophagic vacuoles in skeletal and cardiac muscle. Reportedly, Danon disease is caused by a primary deficiency of a major lysosomal membrane glycoprotein, LAMP2 (lysosome-associated membrane protein 2). Here we review the clinical features, molecular genetics, related animal model, and differential diagnosis of Danon disease.

Danon disease (autophagic vacuolar myopathy): clinicopathologic features of a kindred

Danon disease (autophagic vacuolar myopathy): clinicopathologic features of a kindred

Danon disease (autophagic vacuolar myopathy): clinicopathologic features of a kindred

Danon disease (autophagic vacuolar myopathy): clinicopathologic features of a kindred

LAMP-2 Positive Vacuolar Myopathy with Dilated Cardiomyopathy

We report a 46-year-old male patient with late-onset vacuolar myopathy and dilated cardiomyopathy. Acid maltase activity of the muscle was normal, but the biopsied muscle specimen stained for lysosome-associated membrane protein-2 (LAMP-2), which has recently been reported to be deficient in muscles of patients with Danon disease. The clinical features of the patient are distinct from X-linked myopathy with excessive autophagy, infantile autophagic vacuolar myopathy and autophagic vacuolar myopathy with late-onset and multiorgan involvement (Kaneda).

P.P.3 04 Autophagic vacuolar myopathies: Immunochemical and molecular characterization

Elucidation of mechanisms involved in toxic protein accumulation and vacuole formation in inclusion body myopathies. Accumulation of altered proteins is a common pathogenic mechanism in several neurodegenerative disorders. Skeletal muscle from sporadic inclusion body myositis (s-IBM) and hereditary inclusion body myopathy (h-IBM) patients, similarly to the nervous system in neurodegenerative disorders, typically contains intracellular aggregated protein depositions such as beta amyloid, tau and prion proteins. We examined muscle biopsies from 34 patients with hIBM, sIBM, oculopharyngeal muscle dystrophy, Danon disease, distal dystrophy with rimmed vacuoles, acid maltase deficiency, and genetically unclassified autophagic vacuolar myopathies with distal or proximal weakness. We studied by immunohistochemistry or immunoblot the expression of components of the proteolytic pathways (lysosomal/endosomal, Ca2+-dependent and ubiquitin-proteasomal), and the expression of toxic proteins and of proteins involved in membrane vesicle fusion and membrane repair. We also analysed the GNE gene in 10 patients. We identified abnormal accumulation of toxic proteins and of ubiquitin proteasomal proteins in most examined muscles. Lysosomal/endosomal components were variably expressed in the different pathologies. Vacuoles were positive for sarcolemmal proteins in most cases and accumulated dysferlin in sIBM and in some genetically unclassified autophagic vacuolar myopathies. GNE mutations were detected in two patients. Histopathological and immunochemical features of the autophagic vacuoles may help to distinguish the different clinical entities and give some hints on the origin of vacuoles.

Autophagic Vacuolar Myopathy

Autophagic vacuoles are a frequent feature in numerous neuromuscular disorders. However, they are also pathognomonic morphologic hallmarks in a slowly emerging new group of conditions called autophagic vacuolar myopathies (AVMs), of which Danon disease, originally called "lysosomal glycogen storage disease with normal acid maltase," is the best known entity. Other such conditions, often although not always described from Japan, are X-linked myopathy with excessive authophagy, infantile autophagic vacuolar myopathy, adult-onset autophagic vacuolar myopathy with multiorgan involvement, and X-linked congenital autophagic vacuolar myopathy. Although only 1 protein, the transmembranous lysosomal protein LAMP-2, has been found mutated in Danon disease, the remaining AVMs are genetically still incompletely identified. Several of these conditions not only share autophagic vacuoles, but such autophagic vacuoles also have morphologic properties of the sarcolemma, thus rendering them autophagic vacuoles with sarcolemmal features, an almost pathognomonic phenomenon of this group of disorders.

Autophagic vacuolar myopathy in twin girls

Hereditary autophagic vacuolar myopathy (AVM) may occur in several diseases including the rimmed vacuolar myopathies, acid maltase deficiency, Danon disease, infantile autophagic vacuolar myopathy and X-linked myopathy with excessive autophagy (XMEA). In the latter three conditions the vacuoles are lined by membranes with sarcolemmal features. We present two unusual cases of autophagic vacuolar myopathy in twin girls born at term with no family history of neurological disease. After initial normal developmental milestones they developed progressive leg weakness and wasting with contractures from the age of 12 years. Investigations showed raised CK, normal female karyotype, normal acid maltase activity, normal nerve conduction and myopathic EMG features. Frozen sections of skeletal muscle were stained using routine tinctorial and histochemical methods. Immunohistochemical staining for spectrin, merosin, dystrophin, complement membrane attack complex and sarcoglycans was performed and ultrastructural examination undertaken. Direct sequence analysis of the lamp-2 gene using genomic DNA extracted from lymphocytes was performed. Histological analysis of the muscle biopsies demonstrated myofibres with vacuoles lacking glycogen and lipid many of which were delineated using immunohistochemistry for merosin, dystrophin and sarcoglycans. Ultrastructural examination showed duplication of the myofibre basal lamina with associated autophagic material. Vacuoles within myofibres were either membrane bound containing autophagic material or lined by plasma membrane and basal lamina. Intermyofibrillar glycogen was increased. Sequence analysis of the coding region and intron/exon boundaries of the lamp-2 gene was normal. This is the first report of female cases of AVM with sarcolemmal features. We suggest that these patients may represent manifesting carriers of XMEA, or alternatively, a new form of disease with a similar phenotype having autosomal recessive inheritance.

A new congenital form of X-linked autophagic vacuolar myopathy

In a new family with X-linked congenital autophagic vacuolar myopathy (AVM), seven affected boys presented with congenital hypotonia, dyspnea, and dysphagia with delayed motor milestones. Muscle pathology revealed autophagic vacuoles with sarcolemmal features, multilayered basal lamina with marked sarcolemmal deposition of C5-9 membrane attack complex and calcium, histologically indistinguishable from childhood-onset X-linked myopathy with excessive autophagy (XMEA). Haplotype analysis suggests that this new AVM and XMEA may be allelic despite different clinical presentations.

Congenital X-Linked Autophagic Vacuolar Myopathy

A Chinese-American family with a severe X-linked congenital autophagic vacuolar myopathy (AVM) affecting 7 boys is reported from the National Center of Neurology and Psychiatry, Kodaira, Tokyo, and Utano National Hospital, Kyoto, Japan; and Shandong University, Jinan, China.

Autophagic Vacuoles with Sarcolemmal Features Delineate Danon Disease and Related Myopathies

Among the autophagic vacuolar myopathies (AVMs), a subgroup is characterized pathologically by unusual autophagic vacuoles with sarcolemmal features (AVSF) and includes Danon disease and X-linked myopathy with excessive autophagy. The diagnostic importance and detailed morphologic features of AVSF in different AVMs have not been well established, and the mechanism of AVSF formation is not known. To address these issues, we have performed detailed histologic studies of myopathies with AVSF and other AVMs. In Danon disease and related AVMs, at the light microscopic level, autophagic vacuoles appeared to be accumulations of lysosomes, which, by electron microscopy consisted of clusters of autophagic vacuoles, indicative of autolysosomes. Some autolysosomes were surrounded by membranes with sarcolemmal proteins, acetylcholinesterase activity, and basal lamina. In Danon disease, the number of fibers with AVSF increased linearly with age while the number with autolysosomal accumulations decreased slightly, suggesting that AVSF are produced secondarily in response to autolysosomes. Most of the AVSF form enclosed spaces, indicating that the vacuolar membranes may be formed in situ rather than through sarcolemmal indentation. This unique intracytoplasmic membrane structure was not found in other AVMs. In conclusion, AVSF with acetylcholinesterase activity are autolysosomes surrounded by secondarily generated intracytoplasmic sarcolemma-like structure and delineates a subgroup of AVMs.

Autophagic vacuolar myopathies.

Hereditary myopathies characterized by the development of autophagic vacuoles can be categorized into three groups: rimmed vacuolar myopathies, acid maltase deficiency (glycogen storage disease type II), and myopathies characterized by the autophagic vacuoles with unique vacuolar membranes. Rimmed vacuolar myopathies are most likely secondary lysosomal myopathies because all of the identified causative genes encode extralysosomal proteins. Deficiency of acid maltase, a lysosomal enzyme, has been well characterized clinically, pathologically, biochemically, and genetically, and may become treatable in the near future. The diseases in the last category are relatively rare, but appear to be genetically heterogeneous and the list of these diseases is expanding. Danon disease, the best-characterized disorder in this group, is caused by primary deficiency of a lysosomal membrane protein, LAMP-2. Therefore, diseases in this category are expected to be primary lysosomal disease.

Cardiomyopathy, mental retardation, and autophagic vacuolar myopathy: Abnormal MRI findings in the head

A 21-year-old man with childhood-onset mental retardation, non-obstructive hypertrophic cardiomyopathy, and vacuolar myopathy is presented. A histopathological study of biopsied skeletal muscle showed lysosomal glycogen storage mimicking acid maltase deficiency, but biochemical analysis showed normal acid α-glucosidase activity. Glycogenosomes were also recognized in endothelial cells on electronmicroscopic examination of biopsied skeletal muscle. Magnetic resonance imaging (MRI) findings in the head revealed the involvement of the central nervous system. This is a new type of lysosomal glycogen storage disease with multisystemic involvement. The specific biochemical defect in this disorder remains to be elucidated.