Whole-Exome Sequencing Identifies DYNC2H1 Mutations as a Cause of Jeune Asphyxiating Thoracic Dystrophy Without Extra‐Skeletal Organ Involvement

Abstract

Jeune syndrome, or asphyxiating thoracic dystrophy (JATD), is a rare autosomal recessive skeletal dysplasia with heterogeneous genetic and clinical phenotypes, which primarily affects cartilage and bone development. Herein, we report a patient with a lethal form of SRTD3 without polydactyly (JATD), which led to severe restrictive lung disease and fatal respiratory failure. A full-term boy was born to a 30-year-old mother who was known to have hypothyroidism and was on thyroxine. The parents were first-degree cousins and had one healthy older son. Fetal ultrasound showed a cephalic fetus, normal amniotic fluid and a fundal placenta. All long bones and ribs were below the 1% percentile. The femur was bowed with no fractures or signs of significant demineralization at time of imaging. Head and abdominal circumference were within normal range. An echocardiogram on the 2nd day of life showed severe pulmonary hypertension (PHTN). Nitric oxide was started due to the presence of persistent hypoxia and severe PHTN. The patient continued to require high cardiorespiratory support, but the medical condition worsened, and respiratory failure persisted. The patient died of severe respiratory failure at 16 days of life due to respiratory insufficiency secondary to a severely restricted thoracic cage. Whole-exome sequencing (WES) revealed a homozygous mutation in the DYNC2H1 (NM_001377.3) gene, namely, the c.9041G>T NP_001368.2: p.(Arg3014Ile) missense variant, which results in the substitution of the arginine codon at amino acid position 3014 with an isoleucine codon. The phenotyping of the patient’s JATD and the detection of a homozygous variant in the DYNC2H1 gene confirmed the diagnosis of short-rib thoracic dysplasia-3 without polydactyly. In summary, the patient had isolated skeletal anomalies without polydactyly or other organ involvement. Additionally, the infant had severe PHTN on top of the respiratory failure, which eventually caused death. Considerably more work will need to be done to determine the clinical spectrum of JATD and understand its genetic heterogeneity.