Synonyms: Diastrophic nanism syndrome, diastrophic dwarfism.

Definition: Skeletal dysplasia characterized by predominantly rhizomelic micromelia, flexion limitations of finger joints, extension limitations of the elbows and hips, clubfeet, deformed ear lobes and progressive scoliosis. Typical hand deformities include brachydactyly and symphalangism of the proximal joints of the second through fifth fingers. The thumbs are proximally placed and sub­luxed in abduction. This feature is known as “hitchhiker” thumb. The toes are also affected in the same manner. The phenotypic expression varies from mild to severe forms of disease^1-4. Affected individuals can achieve normal intellectual development.

Etymology: greek: d i a = through and s t r o f h = a twist, a distortion.

Prevalence: The occurrence is undetermined, but it is one of the more common skeletal dysplasias⁵. Six cases have been prenatally diagnosed up to now. M1:F1.

Etiology: Autosomal recessive¹.

Pathogenesis: Destructive process characterized by disorganization and degeneration of the chondrocytes in the resting cartilage. The cartilage matrix contains a decreased amount of collagen fibers, large cystic areas of fibrous tissue and sometimes ossification. This process leads to multiple contractures of the joints that are responsible for the twisted habitus characteristic of this condition^1-4.

Associated anomalies: Bowing of the extremities, cleft palate, micrognathia, facial hemangiomata, anterior chamber eye malformation, craniosynostosis, intracranial calcification, laryngeal or tracheal stenosis, congenital heart disease^1,3-5.

Consequential anomalies: Degenerative arthritis, spinal cord injury, respiratory distress and feeding difficulties^1,4-6.

Differential diagnosis: Achondroplasia, arthrogryposis multiplex congenita, spondyloepiphy­seal dysplasia congenita, meso­melic dysplasia–Nievergelt type and Weissenbacher-Zweymuller syndrome^1,7.

Prognosis:  Severe physical handicap and, in extreme cases, restrictive respiratory distress, due to progressive kyphoscoliosis and arthropathy. The intellect is not affected. Increased neonatal mortality has been reported in these patients^1,4-6,8.

Risk of recurrence: The risk for the patient"s siblings is 25%; the risk for the patient"s children is not increased unless the spouse is a carrier or homozygote³.

Management: The standard obstetrical management should not be altered for this condition. When the diagnosis is made before viability, the option for pregnancy termination can be offered¹.

MESH Dwarfism-diagnosis, Bone-Diseases-development; -diagnosis BDE 0293 MIM 222.600 POS 3185 ICD9 756.4 CDC 756.445

Address correspondence to Luís F. Gonçalves, MD, Vanderbilt University, Dept. of Radiology, 21^st and Garland Avenue, Nashville, TN 37232-5316, Ph: 615-343-0595 Fax: 615-343-4890 Magee- Womens-Hospital, Pittsburgh, PA.

Introduction

Diastrophic dysplasia was described in 1960 by Lamy & Maroteaux^4,9. It is an autosomal recessive skeletal dysplasia characterized by progressive destruction of the cartilage with replacement by fibrous tissue and sometimes bone^1,2,4. The phenotype varies from mild to severe forms. The incidence of the disease is unknown³. Prenatal diagnosis by ultrasound is feasible at early gestational age and has been reported in six instances up to now^6,8,10-13. We present the prenatal findings in two cases of diastrophic dysplasia, one with mild and the other with marked limb shortening.

Case #1

A 30-year-old patient, G1P0, was referred for ultrasound examination at 26 weeks" gestation because of abnormal findings during an outside examination. The examination revealed a male fetus in vertex presentation with short limbs, marked lordosis, narrow chest, narrowing of the spinal canal, an allantois remnant in the umbilical cord, simian crease on the left hand, and proximally displaced and abducted first and second fingers resembling an “OK” sign (fig. 1-9).

Fig. 1: Sagittal view: marked lordosis and a small chest are visible.

Fig. 2: The long bones are short, but otherwise unremarkable. Top: femur; bottom: tibia-fibula.

Fig. 3: The short arms do not extend past the mid-anterior chest, which is hypoplastic.

Fig. 4: Profile view of the face: note the absence of frontal bulging (common in achondroplasia) and the micrognathia.

Fig. 5: Apposition of the first two digits, with a wide gap between the second and third digit, resembles an OK†sign.

Fig. 6: A transverse palmar (simian) crease is visible in the left hand.

Fig. 7: Tangential view of the face: note the low nasal bridge, visible as dark echoes between the eyes.

Fig. 8: Chest X-ray of the newborn.

Fig. 9: X-ray of the hands and feet after delivery.

The measurements are shown in Table 1. The presumptive diagnosis was hetero­zygous achondroplasia. Percutaneous fetal blood sampling at 26 weeks" gestation demonstrated a normal 46 XY karyotype.

The mother was admitted to labor and delivery at 38 weeks because of premature rupture of the membranes. A low transverse cesarean section was performed, delivering a 2,220 g male fetus. Apgar scores were 1 and 2 (1 and 5 minutes). The baby died one hour after birth of respiratory distress.

The external examination at autopsy demonstrated short limbs, proximal insertion of the thumbs, exaggerated spacing between the second and third digits of the hand, bilateral clubfoot and impalpable testes. Internal examination revealed hypoplastic lungs, markedly distended ureters and collecting system of the kidneys, and a 2 mm atrial septal defect. The diagnosis was diastrophic dysplasia.

Fig. 10: The left hand with the finger deformity.

Fig. 11: The newborn: note the hand, joints and limbs.

Case #2

A 27-year-old G₂P₁ patient had a dating ultrasound examination at 14 weeks" gestation. Severe micromelia was present. The measurements for the patient"s three ultrasound examinations at 14, 19 and 36 weeks" gestation are outlined Table 1.

The patient"s past obstetrical history included the delivery of a 4180g male infant with diastrophic dysplasia in 1981. Bilateral clubbed feet were present at the time of the 14-week ultrasound study. The limbs were short (fig. 12-13).

Fig. 12: Case #2: tibia and fibula at 19 weeks.

Fig. 13: Case #2: radius and ulna at 19 weeks.

While the fetal chest was of an appropriate size at 19 weeks" gestation, it had narrowed considerably by the scan that was performed at 36 weeks. Polyhydramnios was present at the 3^rd trimester ultrasound examination.

A 2740g male infant was delivered by repeat cesarean section at 38 weeks" gestation. The diagnosis of diastrophic dysplasia was confirmed in the neonatal period.

Discussion

Incidence

The precise occurrence of diastrophic dysplasia is unknown^3,4. Six cases of prenatal diagnosis have been reported in the literature (Table 2)^6,8,10-13.