ACHONDROGENESIS

Achondrogenesis Type I (Parenti-Fraccaro)

• Autosomal Recessive. Most severe type.
• Defective endochondral and intramembranous ossification.
• Lack of ossification in the calvarium, spine and pelvis.
• Absent sacrum and pubic bone
• Severe micromelia. Short long bones (radius, femur and especially ulna) without bowing.
• Thin ribs with multiple fractures and flared anterior ends.
• Small thorax with a protuberant abdomen.
• Associated malformations include urinary tract duplication, hydronephrosis, cleft palate, ear deformities, corneal clouding and blue sclera, anal atresia and aplastic testis.

Postnatal Speciman
Postnatal Xray

Video clip of Achondrogenesis Type I

Achondrogenesis Type II (Langer-Saldino)

• Defective endochondral ossification only.
• Normal cranial vault ossification differentiates it from type I and osteogenesis imperfecta type II.
• No ossification of the lower lumbar vertebrae or sacrum.
• Ribs are short and horizontal without fractures.
• Irregular flaring of the metaphysis, especially the humerus.
• Redundant soft tissues with subcutaneous edema (hydrops).
• Cystic hygroma / Increased nuchal translucency.
• Polyhydramnios.
• Lethal in utero or soon after birth.
• Differential diagnosis - Thanatophoric dwarf.
• Most cases are sporadic (new autosomal dominant mutation) (5).

Video clip of Achondrogenesis type II

DIFFERENTIAL DIAGNOSIS

• Grebe syndrome.
• Thanatophoric dysplasia.
• Atelosteogenesis type II.
• Hypophosphatasia.

ASSOCIATIONS

There have been two reports of an association between Achondrogenesis type I and II and cystic hygroma (6,7). 

ULTRASOUND

1. Benacerraf B, Osathanondh R, Bieber FR. Achondrogenesis type I: Ultrasound diagnosis in utero. J Clin Ultrasound 1984;12:357-359.
2. Wenstrom KD, Williamson RA, Hoover WW et.al. Achondrogenesis type II (Langer-Saldino) in association with jugular lymphatic obstruction sequence. Prenat Diagn 1989;9:527-532.
3. Rottem S, Bronshtein M, Thaler I et.al. First trimester transvaginal sonographic diagnosis of fetal anomalies. Lancet 1989;i:444-445.
4. Fisk NM, Vaughan J, Smidt M et.al. Transvaginal ultrasound recognition of nuchal edema in the first trimester diagnosis of achondrogenesis. J Clin Ultrasound 1991;19:586-590.
5. Knowlton S, Graves C, Tiller GE. Achondrogenesis. Fetus 1992;2:7564.
6. Wenstrom KD, Williamson RA, Hoover WW et.al. Achondrogenesis type II in association with jugular lymphatic obstruction sequence. Prenat Diagn 1989;9:527-532.
7. Ozeren S, Yuksel A, Tukel T. Prenatal sonographic diagnosis of type I achondrogenesis with a large cystic hygroma. Ultrasound Obstet Gynecol 1999;13:75-76.