·         Achondroplasia (homozygous) - Parents will both be heterozygotes. Rhizomeljc micromelia, normal trunk length, ± cloverleaf skull. These cases are lethal. Lung hypoplasia is a major cause of mortality (due to thoracic narrowing). Noticeable disproportion between skull dimensions/BpD and limb lengths.

 

·         Achondroplasia (heterozygous)- Changes less severe, short limbs, thorax and abdomen narrow. Increased fetal head circumference and BPD, protuberant forehead, narrow interpedicular distance in the spine. Heterozygous disease may not be recognized until late in the second trimester (>24—28 weeks), early sonography being normal. There is rhizomeljc limb (proximal long bones more affected) shortening.

 

·         Achondrogenesis type I- Autosomal recessive lethal dwarfism (Parenti—Houston—Harris). Severe short limbed dwarfism, poorly ossified skull and rest of the skeleton. Marked chest narrowing, the head is not enlarged relative to the trunk. PH is usually present.

 

 

·         Achondrogenesis type II- Autosomal recessive, lethal short limbed dwarfism of long bone type. The head is large relative to the rest of the body, prominent skin folds over a short neck, small chest, distended abdomen with FR, short limbs are held extended away from the body.

 

·         Chondroectodermak dysplasia- (Ellis—Van Creveld syndrome) Autosomal recessive with variable expression. Short limbs, narrow thorax, polydactyly, CHD (50% have a large ASD). Postaxial hexadactyly.

 

 

·         Asphxiating thoracic dystrophy- (Jeune’s syndrome) Autosomal recessive, extremely narrow thorax ± rhizomelic short limb dwarfism ± polydactyly ± renal dysplasia

(renal cysts).

 

·         Osteogenesis imferfecta type IIa-Autosomal dominant, usually lethal; thin skull vault which may collapse, limbs short, thickened and angulated due to multiple fractures.

 

·         Osteogenesis imperfect type I, III, IV-Autosomal dominant or sporadic; has normal body proportions + fractures with normal bone lengths.

 

 

·         Metatrophic dysplasia- Varied inheritance; narrow thorax, kyphoscoliosis relatively long trunk ± tail like appendage over the sacrum.

 

·         Roberts' syndrome- (Pseudothalidomide syndrome) Autosomal recessive with variable expression, tetraphocomelia, midline facial cleft. The chromosomes show a classical abnormality with the centromere region being fluffy.

 

 

·         Diastrophic dysplasia- Autosomal recessive; multiple contractures, hitchhiker’s thumb (more muscle mass than arthrogryposis).

 

·         Short rib- polydactyly syndrome Typle I- (Saldino—NOoflafl) Autosomal recessive. Severely shortened ribs! narrow thorax, short limbs, polydactyly, CVS and genital anomalies, polycystic kidney and pointed metaphysis (important differentiating feature).

 

 

·         Type II-(Majewski) Short limbs, narrow thorax, polydactyly, CVS anomalies, polycystic kidneys, genital anomalies disproportionately short tibia*, cleft lip and palate*. (*Important differentiating feature.)

 

·         Type III- (Naumoff) Short limbs, narrow thorax, polydactyly, CVS and genital anomalies. The metaphysis may be wide with marginal spurs.

 

 

NB- Large polycystic kidneys, occipital encephalocele, microcephaly or polydactyly may be associated with any type of short rib—polydactyly syndrome.

 

 

 

·         Spndyloepiphyseal dysplasia congenital- Autosomal dominant with variable expression, short bowed femora, short spine and trunk (delayed ossification centers, calcaneus and talus).

 

·         Camptomelic dysplasia- Anterior bowing of the lower extremity long bones, anomalies of cervical and thoracic spine with spinal scoliosis and hypoplastic or absent scapulas.

 

 

·         Thanatophoric dyaplasia- Occurs sporadically, represents the most common lethal skeletal dysplasia 14% have a cloverleaf skull (this may be transmitted in an autosomal recessive manner), marked narrowing of the thorax, marked micromelia, soft tissues of limbs may be thickened, enlargement of the head (± prominent forehead), occasional hydrocephalus, PH, more common in male fetuses.

 

·         Fibrochondrogenesis- Autosomal recessive; thin skull vault, poorly echogenic, may be difficult to identify, collapsed sutures occasionally seen, limbs short and thin, ribs thin and poorly visualized, spine poorly mineralized and poorly visualized. Widened metaphyses.

 

 

·         Chondrodysplasia punctata (rhizomelic type) -Severe micromeija of humeri and femora, multiple joint contractures, vertebral body dorsal and ventral ossification separated by a cartilaginous bar.

 

·         Kniest's dysplasia- Autosomal dominant kyphoscoliosis, short trunk, broad thorax. prognosis usually good. Widened metaphyses.

 

 

·         Mesomelic and acromesomelic dysplasia- Autosomal recessive/autosomal dominant; micromelia of middle or distal segments, distribution of shortening differentiates from lethal syndromes.