The loss of function found by RNA-seq and confirmed by western blotting now highlights clinical relevance of the variant within CLPP. CLPP encodes a mitochondrial ATP-dependent endopeptidase34 and CLPP-deficiency causes Perrault syndrome35, 36 (OMIM #601119) which is overlapping with the clinical presentation of the patient investigated here including microcephaly, deafness and severe psychomotor retardation (Supplementary Note 1). Here, CLPP is linked to deafness.