Kearns‐Sayre syndrome case. Novel 5,9 kb mtDNA deletion

BACKGROUND: Kearns‐Sayre syndrome (KSS) is a rare multisystem mitochondrial disorder characterized by onset before 20 years of age and a typical clinical triad: progressive external ophthalmoplegia, pigmentary retinopathy and cardiac conduction anomalies. In most cases KSS is caused by spontaneous heteroplasmic single large‐scale mitochondrial DNA (mtDNA) deletions. Long‐range polymerase chain reaction (LR‐PCR), next generation sequencing (NGS) and multiplex ligation‐dependent probe amplification (MLPA) are the most widely applied methods for the identification of mtDNA deletions. Here, we report the case of 20‐year‐old male who presented with classic Kearns‐Sayre syndrome, confirmed by novel 5,9 kb mtDNA deletion. METHODS AND RESULTS: LR‐PCR and MLPA methods were applied to identify the mitochondrial DNA deletion for the patient, but the results were conflicting. Molecular analysis using primer walking and Sanger sequencing identified a novel 5888 base pairs mtDNA deletion (NC_012920.1:m.6069_11956del) with CAAC nucleotides repeat sequence at the breakpoints. CONCLUSION: Our study enriched the mtDNA variation spectrum associated with KSS and demonstrated the importance of choosing relevant molecular genetic methods.