2. Achondroplasia (Dwarfism)

Definition

Achondroplasia is a hereditary, congenital autosomal dominant disorder that produces abnormalities in the growth and/or remodeling of cartilage and bone affecting the skull, spine, and extremities. The disorder, commonly known as dwarfism, frequently causes a person to be disproportionately short.

Incidence

The recent estimate for the incidence of achondroplasia in the United States is approximately 1:29,000; internationally, the estimate is approximately 1:40,000.

Etiology

Achondroplasia is an autosomal dominant inherited trait. The defect occurs on the short arm of chromosome 4—specifically, band 4p16.3.

Signs and Symptoms

• Abnormal odontoid

• Atlantoaxial instability

• Cleft lip

• Cleft palate

• Clubfoot

• Congenital heart disease

• Congenital odontoid absence

• Genu varum

• Hydrocephalus

• Kyphosis

• Laryngomalacia

• Micrognathia

• Obstructive sleep apnea

• Pulmonary hypertension

• Scoliosis

• Seizure disorder

• Spinal stenosis

• Tracheomalacia

Achrondroplasia (Dwarfism). This girl has short limbs relative to trunk length. She also has a prominent forehead, low nasal root, and redundant skin folds in the arms and legs.

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