3 Achondrogenesis, Type II
581
Langer-Saldino type
Hydropic appearance, prominent forehead, flat face, micrognathia, short trunk, prominent abdomen, micromelia, absent ossification of vertebral bodies, sacrum and pubic bones, early neonatal death Frequency: 0.2 in 100,000 births.
Genetics
Autosomal dominant; occurrence in siblings results from germ cell mosaicism in a parent (OMIM 200610); this phenotype is due to mutations in the COL2A1 gene mapped at 12q13.1-q13.2.
Clinical Features
• Fetal hydrops, polyhydramnios, prematurity, still- birth, neonatal death
• Marked micromelic dwarfism
• Large head, prominent forehead, flat face, cleft palate, micrognathia
• Short trunk, barrel-shaped chest
• Prominent abdomen Differential Diagnosis
• Achondrogenesis types IA and IB
• Hypochondrogenesis
• Grebe achondrogenesis type 2
Radiographic Features Spine
• Absent/deficient ossification of vertebral bodies Chest
• Barrel-shaped thorax
• Variable shortening of ribs
• Unossified sternum Pelvis
• Small iliac wings
• Concave inner and inferior borders of ilia (cres- cent shape)
• Deficient ossification of pubis, sacrum and ischi- um
Extremities
• Very short, bowed long bones (less than in achon- drogenesis type I)
• Metaphyseal flaring and cupping
• Unossified talus and calcaneus Skull
• Enlarged calvarium with satisfactory mineraliza- tion
Bibliography
Borochowitz Z, Ornoy A, Lachman R, Rimoin DL.Achondroge- nesis II-hypochondrogenesis: variability versus hetero- geneity. Am J Med Genet 1986; 24: 273–88
Borochowitz Z, Lachman R, Adomian GE, Spear G, Jones K, Ri- moin DL. Achondrogenesis type I: delineation of further heterogeneity and identification of two distinct subgroups.
J Pediatr 1988; 112: 23–31
Chen H, Liu CT, Yang SS. Achondrogenesis: a review with spe- cial consideration of achondrogenesis type II (Langer- Saldino). Am J Med Genet 1981; 10: 379–94
Gaffney G, Manning N, Boyd PA, Rai V, Gould S, Chamberlain P. Prenatal sonographic diagnosis of skeletal dysplasias – a report of the diagnostic and prognostic accuracy in 35 cas- es. Prenat Diagn 1998; 18: 357–62
Horton WA, Machado MA, Chou JW, Campbell D. Achondroge- nesis type II, abnormalities of extracellular matrix. Pediatr Res 1987; 22: 324–9
Rittler M. Achondrogenesis type II with polydactyly. Am J Med Genet 1995; 59: 157–60
Soothill PW, Vuthiwong C, Rees H. Achondrogenesis type 2 di- agnosed by transvaginal ultrasound at 12 weeks’ gestation.
Prenat Diagn 1993; 13: 523–8
Spranger J. Pattern recognition in bone dysplasias. In: Pa- padatos CJ, Bartsocas CS (eds.) Endocrine genetics and ge- netics of growth. Alan R. Liss, New York, 1985, pp. 315–42
Achondrogenesis, Type II
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