Achondrogenesis Clinical Presentation

Updated: Jan 25, 2019
  • Author: Santina A Zanelli, MD; Chief Editor: Maria Descartes, MD  more...
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Prenatal diagnosis should be suspected in the presence of micromelia, macrocrania with absent or abnormal ossification, and abnormal vertebral ossification. Prenatal history in patients with achondrogenesis may include the following:



Achondrogenesis type I

See the list below:

  • Growth - Lethal neonatal dwarfism, mean birth weight of 1200 g

  • Craniofacial - Disproportionately large head; soft skull; sloping forehead; convex facial plane; flat nasal bridge, occasionally associated with a deep horizontal groove; small nose, often with anteverted nostrils; long philtrum; retrognathia; increased distance between lower lip and lower edge of chin; double chin appearance (often)

  • Neck - Extremely short

  • Thorax - Short and barrel-shaped thorax, lung hypoplasia [10]

  • Abdomen - Protuberant

  • Limbs - Extremely short (micromelia), much shorter than type II; flipper-like appendages

Achondrogenesis type II

See the list below:

  • Growth - Lethal neonatal dwarfism, mean birth weight of 2100 g

  • Craniofacial - Disproportionately large head, large and prominent forehead, flat facial plane, flat nasal bridge, small nose with severely anteverted nostrils, normal philtrum (often), micrognathia

  • Neck - Extremely short

  • Thorax - Short and flared thorax, bell-shaped cage, lung hypoplasia

  • Abdomen - Protuberant

  • Limbs - Extremely short (micromelia)

Common and unique characteristics of the three types of achondrogenesis are summarized in Table 1, below. [11, 12, 13, 14]

Table 1: Achondrogenesis characteristics (Open Table in a new window)

Skull Absent or severely reduced ossification Normal or reduced ossification for age Normal ossification
Long bones

Short and bowed

Stellate, longitudinally oriented

Metaphyseal spurring

Very short, square or stellate

Metaphyseal spurring

Poor ossification of phalanges

Short and bowed

Metaphyseal flaring and cupping


Short, barrel-shaped

Ribs: Short and horizontally oriented, with splayed anterior ends

Multiple fractures (beaded appearance)

Ribs: Short and thin, typically no fractures

Short, barrel- or bell-shaped

Short ribs, no fractures


Vertebral bodies: Absent or rudimentary ossification

Vertebral bodies: Absent or rudimentary central ossification

Vertebral lateral pedicles: Usually ossified


Vertebral bodies and pedicles: Ossified or unossified


Sacrum: Absent or rudimentary ossification

Iliac bone: Abnormal ossification giving a crescent-shaped appearance

Ischium: Not ossified.

Halberd-like iliac bone

Ischial and pubic bones: Unossified