GTR Home > Conditions/Phenotypes > Achondroplasia, severe, with developmental delay and acanthosis nigricans


SADDAN (severe achondroplasia with developmental delay and acanthosis nigricans) is a rare disorder of bone growth characterized by skeletal, brain, and skin abnormalities. All people with this condition have extremely short stature with particularly short arms and legs. Other features include unusual bowing of the leg bones; a small chest with short ribs and curved collar bones; short, broad fingers; and folds of extra skin on the arms and legs. Structural abnormalities of the brain cause seizures, profound developmental delay, and intellectual disability. Several affected individuals also have had episodes in which their breathing slows or stops for short periods (apnea). Acanthosis nigricans, a progressive skin disorder characterized by thick, dark, velvety skin, is another characteristic feature of SADDAN that develops in infancy or early childhood. [from GHR]

Clinical features

  • Intellectual disability, profound
  • Decreased fetal movement
  • Short stature
  • Short thorax
  • Respiratory insufficiency
  • Hearing impairment
  • Kyphosis
  • Hypoplastic ilia
  • Severe platyspondyly
  • Short long bones
  • Bowing of the long bones
  • Small face
  • Cognitive impairment
  • Malar flattening
  • Cloverleaf skull
  • Wide-cupped costochondral junctions
  • Small sacroiliac notches
  • Flared irregular metaphyses
  • Small abnormally formed scapulae
  • Proptosis
  • Platyspondyly
  • Seizure
  • Hydrocephalus
  • Macrocephaly
  • Lethal short-limbed short stature
  • Abnormality of the kidney
  • Short ribs
  • Narrow chest
  • Abnormality of the clavicles
  • Abnormality of the metaphyses
  • Acanthosis nigricans
  • Cutis laxa
  • Brachydactyly syndrome
  • Split hand
  • Muscular hypotonia
  • Limitation of joint mobility
  • Polyhydramnios
  • Defect in the atrial septum
  • Patent ductus arteriosus
  • Frontal bossing
  • Ventriculomegaly
  • Abnormality of neuronal migration
  • Heterotopia
  • Skeletal dysplasia
  • Small foramen magnum
  • Abnormality of the femur
  • Micromelia
  • Abnormality of the fibula
  • Abnormality of the tibia
  • Depressed nasal bridge
  • Aplasia/Hypoplasia of the lungs
  • Increased nuchal translucency
  • Abnormality of the sacroiliac joint
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