Mutation name: None
type: naturally occurring
Comment: Perrault Syndrome Pagon RA 1993 et al.
Perrault syndrome is characterized by sensorineural hearing loss (SNHL) in males and females, and ovarian dysfunction in females. The SNHL is bilateral and ranges in severity from moderate with early-childhood onset to profound with prelingual (congenital) onset to moderate with early-childhood onset. When onset is in early childhood, hearing loss can be progressive. Ovarian dysfunction ranges from gonadal dysgenesis (absent or streak gonads) manifesting as primary amenorrhea to primary ovarian insufficiency (POI) defined as cessation of menses before age 40 years. Fertility in affected males is reported as normal (although the number of reported males is limited). Neurologic features described in some affected women include developmental delay or intellectual disability, cerebellar ataxia, and motor and sensory peripheral neuropathy.
The diagnosis of Perrault syndrome is based on the clinical findings of SNHL in men and women, and ovarian dysfunction in women with a 46,XX karyotype. The diagnosis is confirmed by the presence of biallelic pathogenic variants in one of four genes (HARS2, HSD17B4, LARS2, or CLPP); to date, however, biallelic pathogenic variants in one of these four genes have been identified in individuals in seven families only.
Treatment of manifestations: Hearing loss should be assessed and treated by a multidisciplinary team including an audiologist and otolaryngologist. Possible interventions for those with hearing loss include special educational resources, hearing aids, vibrotactile devices, and cochlear implantation. Cochlear implantation is an option for children older than 12 months with severe-to-profound hearing loss. Primary amenorrhea is treated in adolescents in collaboration with a pediatric endocrinologist in the usual manner first to induce puberty and then to mimic the menstrual cycle and maintain bone health. Assisted reproduction through in vitro fertilization using donor eggs is a consideration for women with gonadal dysgenesis; oocyte cryopreservation can be considered in women at risk for primary ovarian insufficiency. Prevention of secondary complications: In consultation with a reproductive endocrinologist, estrogen replacement treatment should be combined with progesterone to reduce the risk for endometrial cancer. Surveillance: For women with primary amenorrhea: during induction of puberty, follow up every three months for staging of pubertal development and adjustment of estrogen dose. For women on maintenance estrogen replacement therapy: annual follow up as well as approximately every five-year assessment of bone density. Routine audiologic assessments when hearing loss is mild to moderate; no follow up or audiologic assessments when hearing loss is profound. For children with hearing impairment: monitor development Agents/circumstances to avoid: Avoid: ototoxic medication (e.g., aminoglycosides) if alternatives are available; exposure to loud noise, which can exacerbate hearing loss. Evaluation of relatives at risk: It is appropriate to evaluate the older and younger sibs of a proband in order to identify as early as possible those who would benefit from treatment and preventive measures (e.g., early intervention in young children with profound hearing loss).
Perrault syndrome is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk require prior molecular identification of the pathogenic variants causing Perrault syndrome in the family.
Species: C. elegans
type: null mutation
fertility: infertile - ovarian defect
Comment: Mutations in LARS2, encoding mitochondrial leucyl-tRNA synthetase, lead to premature ovarian failure and hearing loss in Perrault syndrome. Pierce SB et al. (2013) The genetic causes of premature ovarian failure (POF) are highly heterogeneous, and causative mutations have been identified in more than ten genes so far. In two families affected by POF accompanied by hearing loss (together, these symptoms compose Perrault syndrome), exome sequencing revealed mutations in LARS2, encoding mitochondrial leucyl-tRNA synthetase: homozygous c.1565C>A (p.Thr522Asn) in a consanguineous Palestinian family and compound heterozygous c.1077delT and c.1886C>T (p.Thr629Met) in a nonconsanguineous Slovenian family. LARS2 c.1077delT leads to a frameshift at codon 360 of the 901 residue protein. LARS2 p.Thr522Asn occurs in the LARS2 catalytic domain at a site conserved from bacteria through mammals. LARS2 p.Thr629Met occurs in the LARS2 leucine-specific domain, which is adjacent to a catalytic loop critical in all species but for which primary sequence is not well conserved. A recently developed method of detecting remote homologies revealed threonine at this site in consensus sequences derived from multiple-species alignments seeded by human and E. coli residues at this region. Yeast complementation indicated that LARS2 c.1077delT is nonfunctional and that LARS2 p.Thr522Asn is partially functional. LARS2 p.Thr629Met was functional in this assay but might be insufficient as a heterozygote with the fully nonfunctional LARS2 c.1077delT allele. A known C. elegans strain with the protein-truncating alteration LARS-2 p.Trp247Ter was confirmed to be sterile. After HARS2, LARS2 is the second gene encoding mitochondrial tRNA synthetase to be found to harbor mutations leading to Perrault syndrome, further supporting a critical role for mitochondria in the maintenance of ovarian function and hearing.//////////////////