Acromesomelic Dysplasia Type I: Maroteaux Type (AMDM)

Genetic inheritance

Autosomal recessive. The responsible defect has been linked to mutations of the Natriuretic Peptide Receptor 2 (NPR2) gene on chromosome 9p13-q12.

Diagnosis

Based on the characteristic clinical and radiographic features in infancy.

Clinical aspects

• Type I: Maroteaux Type (AMDM): Skeletal disorder that affects the limbs and the spine. Newborns affected with AMDM generally are of normal weight, length, and head circumference but can have short appearing limbs. Older children and adults are significantly shorter than their peers, generally of normal intelligence, and are not expected to have any additional medical complications other than their skeletal changes.

• Type II: Hunter-Thompson Type (AMDH): The prevalence is unknown, but seems to be less frequent than the other types of AMD. Dwarfism is present at birth. The adult height is approximately 120 cm. The trunk is normally proportioned. Severe dwarfism is mostly limited to the limbs (extremely short stature), with the legs more severely affected than the arms. The middle segment (forearm with bowing of the radius and posterior dislocation of its head; lower leg with marked shortening of tibia and fibula) and distal segment (short hands and feet) show the most severe changes. Dislocation of the large joints (elbow, hip, knee, ankle) is frequently observed. The fingers usually are very short secondary to cuboidal shape of the metacarpals and shortening of the middle and proximal phalanges. Intelligence, facial appearance, and head circumference are normal. Corneal opacities may occur.

• Type III: Grebe Type (AMDG): Short-limbed dwarfism is affecting both sexes and is evident from birth. The most characteristic features are extremely short limbs, with the legs more severely affected than the upper limbs. The hands are extremely short with toe-like fingers, and the feet are in valgus position. Polydactyly is present in 50% of patients. Facies is normal and obesity is common. Mental development is delayed, but patients ultimately appear mentally normal.

• Type IV: Brahimi-Bacha Type: Spondylometaphyseal dysplasia, most often associated with severe metaphyseal changes and severe genua valgum.

• Type V: Campailla-Martinelli Type: Dwarfism with severe limb shortening, most pronounced in the forearms and lower legs, associated with dysplasia of the tubular bones of the hands and feet. Intelligence is normal.

Anesthetic considerations

Normal craniofacial and axial skeleton. Care with positioning of the limbs due to high risk for dislocations. Otherwise no specific anesthetic considerations.

References