diastrophic dysplasia

the long bones are short and straight. there is bilateral clubbed feet. the big toe is displaced medially. notice the typical abducted position of the thumb hitchhiker thumb.

description

diastrophic dysplasia is characterised by variable micromelic limb shortening, limited joint mobility, clubfoot, micrognathia and cleft palate. there is wide phenotypic variation with milder cases demonstrating rhizomelic shortening. it is usually non-lethal and associated with normal intelligence although a lethal variant and mental retardation have been reported. there is a high prevalence in the finnish population, probably caused by a single ancestral mutation. the gene is located in the long arm of chromosome 5 and encodes a novel sulfate transporter. long term problems are related to cleft palate, scoliosis, spine instability and stenosis and joint abnormalities. the mode of inheritance is autosomal recessive and lethal and non-lethal varieties exist. synonyms include atypical achondroplasia, achondroplasia with clubbed hands and feet; cherub dwarf and diastrophic variant.

diagnosis

the skeletal findings in this condition include short, thick and clubbed tubular bones; short, ovoid first metacarpals with ulnar deviations of the hands and abducted thumbs (hitchhiker thumbs); kyphoscoliosis with normal vertebral bodies and bilateral clubfoot. other anomalies include cauliflower deformity of the ear, congenital heart defects and abnormal laryngeal and tracheal cartilage. prenatal diagnosis is based on the combination of bone shortening, hitchhiker thumbs/toes, clubfeet and normal appearing vertebral bodies and can be made in the early 2nd trimester.

differential diagnosis

in atelosteogenesis type ii the sacrum is horizontal, vertebral body coronal clefts are present, the distal humerus is bifid or tapered, and the hands and feet are more severely affected. spondyloepiphyseal dysplasia congenita has normal appearing hands and feet (with no hitchhiker thumbs or clubfoot), ovoid vertebral bodies and absent ossification of the calcaneus or talus. pseudodiastrophic dysplasia is characterized by a large head, long clavicles, mild platyspondyly, clubfoot and rhizomelic limb shortening. the absence of hitchhiker thumbs can be helpful in the differential diagnosis. jeune and ellis-van creveld syndromes can be differentiated from the milder rhizomelic varieties on the basis of a narrow thoracic cage, polydactyly, and absence of clubfeet and hitchhiker thumbs.

sonographic features

normal head ossification

micrognathia

cleft palate

micromelia or rhizomelia

hitchhiker thumbs/abducted toes

clubfeet joint motion limitation

kyphosis/scoliosis

normal vertebral body ossification

congenital heart defects

associated syndromes

none

references

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hastbacka j, salonen r, laurila p, de la chapelle a, kaitila i prenatal diagnosis of diastrophic dysplasia with polymorphic dna markers j med genet 30:265-268
gembruch u, niesen m, kehrberg h, hansmann m diastrophic dysplasia: a specific prenatal diagnosis by ultrasound prenat diagn 8:539-545
gollop tr, eigier a prenatal ultrasound diagnosis of diastrophic dysplasia at 16 weeks am j med genet 27:321-324
kaitila i, ammala p, karjalainen o, liukkonen s, rapola j early prenatal detection of diastrophic dysplasia prenat diagn 3:237-244
o’brien gd, rodeck c, queenan jt early prenatal diagnosis of diastrophic dwarfism by ultrasound br med j 280:1300
goncalvez lf, jeanty p diastrophic dysplasia the fetus 2:7564-7-12
babcook cj, filly ra diastrophic dysplasia the fetus 3:7564-19-22
mantagos s, weiss rr, mahoney m, hobbins j prenatal diagnosis of diastrophic dwarfism am j obstet gynecol 139:111-113
horton wa, rimoin dl, lachman rs, skovby f, hollister dw, spranger j, scott ci, hall jg the phenotypic variability of diastrophic dysplasia j pediatr 93:609-613