Functional assessment using short tests in a patient with pompe disease receiving enzyme replacement therapy: case report

ABSTRACT Introduction: Pompe disease is characterized by the deficiency of the acid alfa glucosidase enzyme, which leads to a glycogen accumulation mainly in cardiac and skeletal muscles. Its onset may be early or late; the late form is more difficult to handle given the variety of presentations. Enzyme replacement therapy has shown to improve gross motor function and lung function in patients. Case description: Female patient who presented chronic quadriparesis. She was diagnosed with Pompe disease, which required enzyme replacement therapy that helped improve the symptoms, which was evident with the performance of rapid functional evaluation tests. Discussion: Enzyme replacement therapy in Pompe disease modifies the natural history of the disease. A brief review of the literature about the functional tests that can be used to assess a patient with this disorder is presented. Conclusion: The 10-meter walk test, one-leg stance test, cervical flexion in supine position, five times sit to stand test, and coin rotation task are useful for clinical evaluation in patients with Pompe disease receiving enzyme replacement therapy.

RESUMEN Introducción. La enfermedad de Pompe se caracteriza por una alteración de la enzima alfa glucosidasa ácida lisosomal que produce acumulación de glicógeno, principalmente en el músculo esquelético y cardiaco. Se presentan formas de inicio temprano y tardío, esta última de más difícil manejo dada la múltiple variedad de presentaciones. La terapia de reemplazo enzimático ha demostrado mejorar la función motora gruesa y pulmonar de los pacientes con esta patología. Presentación del caso. Paciente femenino quien presentó cuadro crónico de cuadriparesia y a quien se le documentó enfermedad de Pompe, por lo que requirió terapia de reemplazo enzimático con mejoría franca de sintomatología, objetivizada con la realización de pruebas rápidas de evaluación funcional. Discusión. La terapia de reemplazo enzimático en la enfermedad de Pompe modifica la historia natural de la enfermedad. Se realiza una breve revisión de la literatura acerca de las pruebas funcionales que pueden ser utilizadas dentro de la evaluación del paciente con este trastorno. Conclusiones. La prueba de caminata de 10m, de equilibrio monopodal, de flexión cervical en supino, de levantarse-sentarse cinco veces y de la moneda resultan útiles para la evaluación clínica de los pacientes con enfermedad de Pompe en terapia de remplazo enzimático.

A family with Danon disease caused by a splice site mutation in LAMP2 that generates a truncated protein.

BACKGROUND: Danon disease is an X-linked dominant hereditary condition caused by mutations in the gene encoding lysosomal-associated membrane protein 2 (LAMP2), leading to failure of lysosome binding to autophagosomes, accumulation of glycogen in the heart, and abnormal cardiac function. METHODS: We describe identification of a mutation in LAMP2, c.741+1G>T, in a family with Danon disease by whole exome sequencing. RESULTS: Pathology examination of patient skeletal muscle biopsy showed myogenic damage and autophagic vacuoles with sarcolemmal features (AVSF). Numerous autophagic vacuoles accumulated in muscle cells were detected by electron microscopy, indicating abnormal autophagy function. CONCLUSION: The mutation did not result in loss of mRNA exons; rather, a 6-nucleotide (two-codon) insertion, where the latter was a stop codon, leading to early termination of LAMP2 protein translation. The resulting truncated protein lacks an important transmembrane domain, which will impair lysosome/autophagosome fusion, damage autophagy function, and result in the clinical manifestations of Danon disease.

Amelioration of X-Linked Related Autophagy Failure in Danon Disease With DNA Methylation Inhibitor.

BACKGROUND: Danon disease is an X-linked disorder that leads to fatal cardiomyopathy caused by a deficiency in lysosome-associated membrane protein-2 (LAMP2). In female patients, a later onset and less severe clinical phenotype have been attributed to the random inactivation of the X chromosome carrying the mutant diseased allele. We generated a patient-specific induced pluripotent stem cell (iPSCs)-based model of Danon disease to evaluate the therapeutic potential of Xi-chromosome reactivation using a DNA methylation inhibitor. METHODS: Using whole-exome sequencing, we identified a nonsense mutation (c.520C>T, exon 4) of the LAMP2 gene in a family with Danon disease. We generated iPSC lines from somatic cells derived from the affected mother and her 2 sons, and we then differentiated them into cardiomyocytes (iPSC-CMs) for modeling the histological and functional signatures, including autophagy failure of Danon disease. RESULTS: Our iPSC-CM platform provides evidence that random inactivation of the wild-type and mutant LAMP2 alleles on the X chromosome is responsible for the unusual phenotype in female patients with Danon disease. In vitro, iPSC-CMs from these patients reproduced the histological features and autophagy failure of Danon disease. Administration of the DNA demethylating agent 5-aza-2'-deoxycytidine reactivated the silent LAMP2 allele in iPSCs and iPSC-CMs in female patients with Danon disease and ameliorated their autophagy failure, supporting the application of a patient-specific iPSC platform for disease modeling and drug screening. CONCLUSIONS: Our iPSC-CM platform provides novel mechanistic and therapeutic insights into the contribution of random X chromosome inactivation to disease phenotype in X-linked Danon disease.

Asymptomatic young man with Danon disease.

Danon disease is a rare, codominant X-linked genetic disorder characterized by the triad of left ventricular hypertrophy, mental retardation, and peripheral myopathy. This disease is caused by mutations in the gene that encodes lysosomal associated membrane protein 2 (LAMP2), a deficiency of which results in the accumulation of autophagic granular débris within the vacuoles of muscle cells. This is a report of an asymptomatic 19-year-old man with Danon disease in the absence of mental retardation or clinically significant skeletal myopathy. This case underscores the importance of accurate diagnosis of unexplained left ventricular hypertrophy, in order to establish an appropriate treatment plan and to advise genetic counseling.