Hearing loss in a patient with the myopathic form of mitochondrial DNA depletion syndrome and a novel mutation in the TK2 gene.
Mitochondrial DNA (mtDNA) depletion syndrome (MDS) is a devastating disorder of infancy caused by a significant reduction of the number of copies of mitochondrial DNA in one or more tissues. We report a Spanish patient with the myopathic form of MDS, harboring two mutations in the thymidine kinase 2 gene (TK2): a previously reported deletion (p.K244del) and a novel nucleotide duplication in the exon 2, generating a frameshift and premature stop codon. Sensorineural hearing loss was a predominant symptom in the patient and a novel feature of MDS due to TK2 mutations. The patient survived up to the age of 8.5 y, which confirms that survival above the age of 5 y is not infrequent in patients with MDS due to TK2 deficiency.
Martí
Ramon
R
Laboratory of Mitochondrial Disorders, Institut de Recerca Hospital Universitari Vall d'Hebron, 08035 Barcelona, Spain.
Nascimento
Andrés
A
Colomer
Jaume
J
Lara
Mari C
MC
López-Gallardo
Ester
E
Ruiz-Pesini
Eduardo
E
Montoya
Julio
J
Andreu
Antoni L
AL
Briones
Paz
P
Pineda
Mercè
M
D001483:Base Sequence; D002648:Child; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism*; D034381:Hearing Loss / Q000209:etiology* / Q000235:genetics*; D006801:Humans; D008297:Male; D017240:Mitochondrial Myopathies / Q000150:complications* / Q000235:genetics*; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D013030:Spain; D013577:Syndrome; D013937:Thymidine Kinase / Q000235:genetics*
D004272:DNA, Mitochondrial; C105339:thymidine kinase 2; D013937:Thymidine Kinase