Abstract: 【Abstract】 Objective To identify gene mutations in the BCS1L gene in a patient with Bj-rnstad syndrome mainly manifesting as congenital pili torti and sensorineural hearing loss. Methods Clinical data were collected and DNA was extracted from the peripheral blood of the patient and her parents. All the exons and their flanking sequences of the BCS1L gene were amplified by PCR followed by Sanger sequencing, and the sequencing results were compared with the normal sequences. A few hairs were collected from the patient, and examined by the scanning electron microscope. Results There were two mutations in BCS1L gene in the patient, i.e., a heterozygous nonsense mutation in exon 4 and a heterozygous missense mutation in exon 8. The nonsense mutation in exon 4, which caused a change from CGA to TGA at position 144 and resulted in the substitution of arginine by termination codon（p.R144*）, was a novel mutation in the BCS1L gene causing Bj-rnstad syndrome, and had never been reported in the literature. The missense mutation in exon 8 led to a change from CGC to CAC at position 306 and resulted in the substitution of arginine by histidine （p.R306H）. The patient′s mother only carried a heterozygous mutation c.430 C>T （p.R144*） in exon 4 of the BCS1L gene, and her father only carried a heterozygous mutation c.917 G>A （p.R306H） in exon 8 of the BCS1L gene. Scanning electron microscopy showed that flats, grooves and longitudinal twisting irregularly appeared at intervals on the surface of hair shafts. Conclusions A novel mutation in the BCS1L gene, which causes a change from CGA to TGA at position 144 in the BCS1L gene and results in a premature termination codon, is firstly reported in a patient with Bj-rnstad syndrome, and the compound heterozygous mutations c.430 C>T and c.917 G>A in the BCS1L gene are associated with the clinical manifestations of the patient. Genetic analysis is helpful for the diagnosis of Bj-rnstad syndrome.

Key words: Mitochondrial diseases, Genes, mitochondrial, DNA mutational analysis, Bj-rnstad syndrome, BCS1L gene