Gracile bone dysplasia

Alternate names

Skeletal dysplasia lethal with gracile bones; Osteocraniostenosis; Osteocraniosplenic syndrome; Habrodysplasia

Definition

Osteocraniostenosis is a lethal skeletal dysplasia characterized by a cloverleaf skull anomaly, facial dysmorphism, limb shortness, splenic hypo/aplasia and radiological anomalies including thin tubular bones with flared metaphyses and deficient calvarial mineralization.

Epidemiology

First described in 1989, less than 30 cases have been reported so far.

Cause

• Etiology of osteocraniostenosis is not well known, but some histological findings report growth plate disorganization and adjacent diaphyseal ossification.
• Recently, heterozygous mutations of the FAM111A gene, encoding a protein of unknown function and responsible of some autosomal dominant forms of Kenny-Caffey syndrome with hypothyroidism and slender and dense bone, have been identified in patients with osteocraniostenosis.
• A clinical and genetic heterogeneity remains likely.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

It shows an autosomal dominant mode of inheritance with a majority of de novo mutations.

Signs and symptoms

This syndrome is characterized by dysmorphic features of the fetus and the newborn: the skull is misshapen, combining acrocephaly and cloverleaf deformity, fontanelles are very large; facial dysmorphism includes midface hypoplasia with telecanthus, short upturned nose, short philtrum, small inverted V-shaped mouth and low-set ears; limbs are also affected with bowed forearms, micromelia and acromicria with brachydactyly.'

Diagnosis

• Diagnosis is based mainly on radiological and pathological examination.
• Radiological examination reveals hypomineralisation of the skull, flat and dense vertebral bodies, thin tubular bones with flared and dense metaphyses, brachymetacarpia and brachyphalangy with diabolo appearance (very thin tubular bones with abrupt metaphyseal flare) and lack of ossification of the distal phalanges.
• The spleen is hypoplasic or even absent.
• Diaphyseal fractures are frequent at birth.

Differential diagnosis Differential diagnosis includes the hypo/akinesia sequence, Hallermann-Streiff-FranÁois syndrome, Kenny-Caffey syndrome and other slender bone dysplasias, and some cases of osteogenesis imperfecta with slender bones .

Treatment

There is no treatment for osteocraniostenosis.

Prognosis

Prognosis is very poor as most cases are stillborn or die in their first days of life.

NIH genetic and rare disease info

• NIH info on Gracile bone dysplasia

Gracile bone dysplasia is a rare disease.