Asymptomatic hyperCKemia in a case of Danon disease due to a missense mutation in Lamp-2 gene

Primary lysosome-associated membrane protein-2 (LAMP-2) deficiency is an X-linked disease, characterized by the clinical triad of cardiomyopathy, vacuolar myopathy and mental retardation, previously known as Danon disease. Mutations of lamp-2 gene have been reported so far in about 20 patients, one of whom was Italian. We describe a new Italian case with persistent hyperCKemia, exercise intolerance and hypertrophic cardiomyopathy but with no muscle weakness or mental impairment. Muscle biopsy revealed a vacuolar myopathy with mild glycogen storage, and immunohistochemical studies detected LAMP-2 deficiency. A new nucleotide substitution (T961C) on exon 8 of lamp-2 gene was identified as responsible for the protein deficiency. This is the first missense mutation so far described. LAMP-2 deficiency should be considered as a cause of recurrent hyperCKemia and hypertrophic cardiomyopathy.     

Novel Lamp-2 gene mutation and successful treatment with heart transplantation in a large family with Danon disease

Lysosome-associated membrane protein-2 deficiency (LAMP-2 deficiency), or Danon disease, is a rare X-linked lysosomal disease characterized by cardiomyopathy, vacuolar myopathy, and mental retardation. Less than 20 families with mutations of the Lamp-2 gene have been reported. We describe a family from Sardinia with eight affected patients (4 females and 4 males) and a novel mutation in exon 2 of the Lamp-2 gene (c.102_103delAG). Females developed isolated cardiomyopathy in adulthood, whereas males presented with cardiomyopathy, myopathy, and mental retardation before the age of 20 years. Cardiomyopathy was lethal in three females in their 40s and in three males before the age 20 years. One patient was successfully treated by heart transplantation with more than 5-year follow-up. This study demonstrates that Danon disease is a frequently fatal condition that is potentially treatable with heart transplantation.     

Characterization of Danon disease in a male patient and his affected mother

Danon disease, primary lysosome-associated membrane protein-2 (LAMP-2) deficiency, is histologically characterized by unusual vacuoles bound by membranes with sarcolemmal features in skeletal muscle. We studied skeletal muscle specimens from a male patient with genetically confirmed Danon disease who had two muscle biopsies, at age 20 months and 16 years, and from his mother with cardiomyopathy but without clinically apparent skeletal myopathy. In the patient, the number of vacuoles increased over the 14-year interval between biopsies, suggesting that the number of vacuolated fibers increases with age, and correlates with the development of muscle symptoms. In contrast, in the muscle biopsy from the mother there were no vacuoles even though she had decreased LAMP-2.     

Morphological, clinical and genetic aspects in a family with a novel LAMP-2 gene mutation (Danon disease)

A family with several cases of severe cardiomyopathy and moderate myopathy is described, affecting two brothers and their cousin as well as their mothers. One boy died of sudden cardiac arrest at 17 years of age. The two brothers were treated with an implantable defibrillator and their mother died suddenly at 40 years of age. Muscle biopsy in males showed vacuolar myopathy in two cases, and no abnormality on standard staining in the third case. Cardiac biopsies showed hypertrophic and vacuolated fibres. Complete absence of LAMP-2 was demonstrated by immunohistochemistry on the vacuolated skeletal and cardiac muscle, but also on the morphologically normal skeletal muscle. Sequencing of LAMP-2 gene showed a novel S157X mutation in exon 4. Danon disease is a rare and potentially lethal cause of hypertrophic cardiomyopathy. Diagnosis can be made by immunohistochemistry performed on cardiac or muscle biopsy, and confirmed by genetic analysis, which also allows for easy family screening and counselling.     

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.     

Danon disease: an unusual presentation of autism

Danon disease is an X-linked cardioskeletal myopathy, originally reported as "lysosomal glycogen storage disease with normal acid maltase," resulting from a primary deficiency of lysosome-associated membrane protein-2 because of mutations in the lysosome-associated membrane protein-2 gene. Classic clinical features in males include cardiomyopathy (100%, eventually), myopathy (90%), and mental retardation (70%), but mostly of a mild degree. We report on an unusual presentation in a patient with autism, motor delay, and a normal cardiac evaluation. The presence of multiorgan involvement, including elevated liver enzymes, abnormal cranial magnetic resonance imaging, and diffuse hypotonia with swallowing difficulties, prompted a muscle biopsy. A quadriceps muscle biopsy was performed, and the findings were most suspicious for a glycogen storage-type disease. Subsequently, a pathogenic lysosome-associated membrane protein-2 mutation was found. To our knowledge, there are no previous clinical reports of autism in children with Danon disease.     

Early onset of cardiomyopathy and intellectual disability in a girl with Danon disease associated with a de novo novel mutation of the LAMP2 gene

Danon disease, primary lysosome‐associated membrane protein‐2 (LAMP‐2) deficiency, is characterized clinically by cardiomyopathy, myopathy and intellectual disability in boys. Because Danon disease is inherited in an X‐linked dominant fashion, males are more severely affected than females, who usually have only cardiomyopathy without myopathy or intellectual disability; moreover, the onset of symptoms in females is usually in adulthood. We describe a girl with Danon disease who presented with hypertrophic cardiomyopathy and Wolff‐Parkinson‐White (WPW) syndrome at 12 years of age. Subsequently, she showed signs of mild learning disability and intellectual disability on psychological examinations. She had a de novo novel mutation in the LAMP‐2 gene and harbored an identical c.749C > A (p.Ser250X) variant, resulting in a stop codon in exon 6. She showed decreased, but not completely absent LAMP‐2 expression on immunohistochemical and Western blot analyses of a skeletal muscle biopsy specimen, which has been suggested to be caused by a 50% reduction in LAMP‐2 expression (LAMP‐2 haploinsufficiency) in female patients with Danon disease caused by a heterozygous null mutation. To our knowledge, our patient is one of the youngest female patients to have been given a diagnosis of Danon disease. In addition, this is the first documented case in a girl that was clearly associated with intellectual disability, which is very rare in females with Danon disease. Our findings suggest that studies of female patients with Danon disease can extend our understanding of the clinical features of this rare disease.     

A 13‐year‐old girl with proximal weakness and hypertrophic cardiomyopathy with danon disease

Danon disease is caused by deficiency of lysosome‐associated membrane protein‐2 (LAMP‐2). It is characterized clinically by cardiomyopathy, myopathy, and mental retardation in boys. Herein we report a 13‐year‐old female patient with Danon disease who presented with early‐onset skeletal myopathy and cardiomyopathy. She had a de novo novel mutation in the LAMP2 gene, and her muscles showed many autophagic vacuoles with sarcolemmal features and complete absence of LAMP‐2 expression. To the best of our knowledge, this girl is one of the earliest‐onset manifesting carriers of Danon disease with typical muscle pathology. Muscle Nerve, 2010     

Identification of a novel LAMP2 mutation responsible for X-chromosomal dominant Danon disease

Danon disease (DD) is a rare lysosomal glycogen storage disease with normal acid maltase activity, which is characterised clinically by cardiomyopathy and myopathy, and a variable degree of mental retardation. The causative gene, LAMP2, has been mapped to chromosome Xq24-q25. LAMP2 encodes a lysosome-associated membrane glycoprotein. We identified a novel LAMP2 mutation of the exon 8 splice acceptor site (IVS7-1G --> A) in an affected male and female, which predicts abnormal splicing. Both affected individuals presented solely with hypertrophic cardiomyopathy. Muscle weakness and mental impairment were absent. Diagnosis of Danon disease was established by muscle biopsy, when the male index patient developed transient severe muscle weakness following heart transplantation. Typical biopsy findings were also found in a heart muscle specimen. Demonstration of the LAMP2 mutation in affected male and female siblings is compatible with X-linked dominant inheritance. Danon disease should be actively looked for in cardiomyopathy patients.     

Mild form of Danon disease: two case reports

Danon disease is typically lethal by the mid-twenties in male patients due to cardiomyopathy. This report aims to describe two unrelated male patients showing mild manifestations of the disease. A 39-year-old man presented with a 10-year history of elevated serum creatine kinase levels with slowly progressive muscle weakness. Muscle pathology showed autophagic vacuoles with sarcolemmal features. Genetic testing revealed a hemizygous mutation in exon 9b, an alternatively spliced exon, of lysosome-associated membrane protein-2 (LAMP-2) (c.1097_1098delAA). Cardiac testing showed asymptomatic mild left ventricular hypertrophy. He had borderline intelligence. Early stage of retinopathy was detected. Another male patient, currently 53-year-old, had asymptomatic supraventricular extrasystole and muscle weakness but no intellectual disability, harboring the same mutation. He also had retinopathy. The present patients commonly carry a mutation in exon 9b of LAMP-2, suggesting that mutations in the exon are associated with a mild form of Danon disease.     

Infantile autophagic vacuolar myopathy is distinct from Danon disease

Lysosomal glycogen storage disease with normal acid maltase (Danon) is caused by primary lysosome-associated membrane protein-2 (LAMP-2) deficiency. Typically, the disease begins after the first decade; however, two infantile patients had similar histologic features. The infantile disorder is distinct from Danon disease, because, in both infants, LAMP-2 protein is present in skeletal muscle. Deposition of C5b-9 and multilayered basal lamina in one patient suggest that the infantile disease is pathogenically similar to X-linked myopathy with excessive autophagy.     

Clinicopathological features of genetically confirmed Danon disease

BACKGROUND: Danon disease is due to primary deficiency of lysosome-associated membrane protein-2. OBJECTIVE: To define the clinicopathologic features of Danon disease. METHODS: The features of 20 affected men and 18 affected women in 13 families with genetically confirmed Danon disease were reviewed. RESULTS: All patients had cardiomyopathy, 18 of 20 male patients (90%) and 6 of 18 female patients (33%) had skeletal myopathy, and 14 of 20 male patients (70%) and one of 18 female patients (6%) had mental retardation. Men were affected before age 20 years whereas most affected women developed cardiomyopathy in adulthood. Muscle histology revealed basophilic vacuoles that contain acid phosphatase-positive material within membranes that lack lysosome-associated membrane protein-2. Heart transplantation is the most effective treatment for the otherwise lethal cardiomyopathy. CONCLUSIONS: Danon disease is an X-linked dominant multisystem disorder affecting predominantly cardiac and skeletal muscles.     

Danon's disease (X-linked vacuolar cardiomyopathy and myopathy): a case with a novel Lamp-2 gene mutation

Herein, we report a new case of Danon's disease in a 41-year-old Frenchman. This patient displays the typical clinical triad, with cardiomyopathy, mental retardation and myopathy, and a vacuolar myopathy without acid alpha-glucosidase deficiency. He has also developed a diffuse chorio-capillary ocular atrophy, and represents the second case of successful heart transplantation in this lysosomal disease. Interestingly, analysis of LAMP-2 protein expression in cultured fibroblasts revealed a primary deficiency of this lysosomal membrane protein. This defect resulted from a yet undescribed deletion in exon 7 of lamp-2 gene.     

Danon disease: a novel Lamp-2 gene mutation in a family with four affected members

This is a report of a family with four members affected with Danon disease and variable clinical presentations, including cardiomyopathy, skeletal muscle pathology, and hepatopathy. Analysis by electron microscopy of the quadriceps muscle from the proband and his brother showed abnormal mitochondria, and immunohistochemistry revealed no expression of LAMP-2 protein. This defect is due to a yet undescribed mutation located at the second nucleotide in the intron 8 of the Lamp-2 gene (c.1093+2 T>A) that generated exon 8 skipping confirmed at RNA level in the proband.     

Lysosomal glycogen storage disease with normal acid maltase with early fatal outcome

In a male infant who had cardiomyopathy, generalized muscle weakness and increased serum creatine kinase levels, his muscle biopsy revealed myopathic changes with tiny intracytoplasmic vacuoles containing PAS-positive material and high acid phosphatase activity, but had normal acid maltase activity biochemically. These findings were consistent with those seen in lysosomal glycogen storage disease with normal acid maltase (Danon disease). Sarcolemmal indentations commonly seen in this disease were missing, but a complement membrane attack complex, C5b-9 was positive along the surface membrane of the muscle fibers as seen in X-linked vacuolar myopathy. The patient was on a respirator and died at 27 months of age from pneumonia and hypertrophic cardiomyopathy. Lysosomal glycogen storage disease with normal acid maltase may be manifested at birth with marked skeletal and cardiac involvement leading to death in early infancy.     

Successful carnitine treatment in two siblings having lipid storage myopathy with hypertrophic cardiomyopathy

Two Japanese siblings had lipid storage myopathy with hypertrophic cardiomyopathy (HCM). They had slowly progressive muscle weakness and ventricular hypertrophy of the heart evidenced by electrocardiography and echocardiography. Their developmental milestones were normal until three years of age when mild weakness in the lower limbs became evident. Laboratory examination showed transient high creatine kinase levels (CK) and hyperammonemia. Histochemical investigation on the muscles revealed abnormal accumulation of sudanophilic lipid droplets predominantly in type 1 fibers, type 2 A fiber atrophy and type 2 B fiber deficiency. In case 1, excessive lipid droplets were also observed in the biopsied cardiac muscle. Carnitine was decreased in the skeletal muscles and the serum. Treatment with DL-carnitine to both cases resulted in marked clinical improvement and decreased lipid droplets in the muscles.     

Functional performance and muscle strength phenotypes in men and women with Danon disease

Danon disease is a rare X-linked myopathy that is characterized clinically by a triad of cardiomyopathy, skeletal myopathy, and cognitive impairment. The purpose of this investigation was to quantify functional performance, muscle weakness, and quadriceps activation in individuals with Danon disease as compared with healthy individuals. Four males (ages 10-34 years) and 4 females (ages 16-50 years), with the genetic markers of Danon disease, were compared with 8 healthy males (ages 22-34 years) and 8 healthy females (ages 23-41 years) and previously reported norms. Affected males and females had decreased functional performance, significant generalized muscle weakness, and decreased quadriceps strength and activation when compared with healthy individuals. Affected males had larger deficits in function, strength, and activation when compared with affected females. The results indicate that, although the presentation of Danon disease is variable and is typically only described in males, muscle weakness patterns exist in both affected males and females.     

Defects of the mitochondrial respiratory chain complexes in three pediatric cases with hypotonia and cardiac involvement.

Three children displaying hypotonia, cardiac involvement and defects of the mitochondrial respiratory chain complexes are reported. The first case showed severe neonatal hypotonia, failure to thrive, hepatomegaly, dilation of the right cardiac cavities, profound lactic acidosis and amino aciduria. The boy died at the age of 7 weeks. In the second case hypotonia, severe cardiomyopathy, cyclic neutropenia, lactic acidosis and 3-methylglutaconic aciduria occurred. The boy died at the age of 27 months. The third case presented at the age of 16 months as an acute hypokinetic hypertrophic cardiomyopathy with transient hypotonia and mild lactic acidosis. Spontaneous clinical remission occurred. In all cases muscle biopsy was performed. Morphological studies failed to show ragged-red fibers but there was lipid storage myopathy and decreased cytochrome c oxidase activity. Biochemical studies confirmed the cytochrome c oxidase deficiency in muscle in all cases. It was associated with complex I III deficiency in case 1 and with severe deficits of all respiratory chain complexes in case 2. Post-mortem studies in case 1 indicated that complex IV was reduced in the liver but not in the heart and quantitative analysis of mtDNA revealed a depletion in muscle. Cases 1 and 2 shared some clinical features with fatal infantile myopathy associated with cytochrome c oxidase deficiency, while case 3 displayed a very unusual clinical presentation. The histochemical enzyme reaction of cytochrome c oxidase is useful for the diagnosis of mitochondrial myopathy because ragged-red fibers may be lacking. Finally, biochemical measurement of the different mitochondrial respiratory chain complexes is required because multiple defects are frequent and occasionally related to mtDNA depletion.