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Lethal osteosclerotic bone dysplasia
A rare disorder defined by generalized osteosclerosis with periosteal bone formation, characteristic facial dysmorphism, brain abnormalities including intracerebral calcifications, and neonatal lethal course.
ORPHA:1832Classification level: Disorder
Ten cases in eight families have been reported, the majority of a Middle East origin. Parental consanguinity was frequently present.
The cranial features are a wide anterior fontanelle, expressed proptosis with everted lower eyelids, severely depressed nasal bridge, small nose, low-set ears, and severe midface hypoplasia leading to choanal atresia. The mouth is usually triangular, gum hypertrophy is expressed, and there may be natal teeth and cleft palate/uvula. The radiological findings include generalized osteosclerosis of all bones and the base of the skull, with cortical hyperostosis and periosteal new bone formation. An obtuse mandibular angle is characteristic, as are irregularly formed ribs. Radiologically, widespread bilateral calcification in the periventricular white matter, basal ganglia, and thalamus is found and in some cases calcifications are also seen in the corpus callosum, falx, tentorium, and meninges. Extra-skeletal features can be hydronephrosis and ureteral stenosis.
Mutations in the FAM20C gene have a causative role in lethal osteosclerotic bone dysplasia.
Diagnosis is based on clinical presentation and calcification demonstrable by ultrasound, plain X-rays and computing tomography (CT).
Prenatal diagnosis by ultrasound or molecular testing is feasible.
The condition is transmitted in an autosomal recessive manner.