Identification of two novel homozygous mutations in ERCC8 gene in two unrelated consanguineous families with Cockayne syndrome from Iran

•Identification of two novel homozygous mutations in ERCC8 gene.•WES result together with the characteristic clinical evaluation provided accurate diagnosis for two patients.•Accurate diagnosis provide genetic counseling and prenatal diagnosis to minimize new affected persons. Cockayne syndrome (CS) is a rare autosomal recessive disorder with characteristic multisystem involvement including pre- or post-natal growth failure, progressive neurological dysfunction, psychomotor retardation, cerebral atrophy, microcephaly and mental retardation, due to mutations in either the ERCC8/CSA or ERCC6/CSB gene. We present two Iranian patients with remarkable growth failure, developmental delay, microcephaly, severe speech delay, vision problem, sun sensitivity, hearing loss, dental anomalies, unstable gait, mild contractures in knees, kyphosis and spasticity in lower limbs, balance disorders and typical dysmorphic features including long nose, aged face, large ears and sunken eyes. Clinical evaluation, magnetic resonance imaging, Peripheral blood karyotype, Multiplex ligation-dependent probe amplification (MLPA), and whole-exome sequencing were used to characterize etiology in two patients from two unrelated consanguineous families of Iranian descent with Cockayne syndrome. We detected two novel pathogenic mutations in two unrelated families, a homozygous duplication mutation (c.317_320dupAGTG, p.Trp107Ter) and a splicing variant (c.481 + 1G > A) in ERCC8 gene. WES results together with the characteristic clinical manifestations of Cockayne syndrome, provided an accurate diagnosis for two patients. Also, our study identified two novel variants in Iranian families.