A phenotype intermediate between Desbuquois dysplasia and diastrophic dysplasia secondary to mutations in DTDST.

We describe a child whose original clinical and radiologic manifestations led to a diagnosis of Desbuquois dysplasia. Subsequent development of features including cervical kyphosis and cystic ears caused us to reconsider the original diagnosis. The new complement of features in this patient fell in a range between Desbuquois dysplasia and diastrophic dysplasia. Molecular testing showed that she is a compound heterozygote for mutations in the diastrophic dysplasia sulfate transporter gene (DTDST). This finding confirms that there is locus heterogeneity in apparent Desbuquois dysplasia. It also expands the phenotypic spectrum of disorders caused by mutations in DTDST.

Absence of correlation between infantile hypotonia and foramen magnum size in achondroplasia.

Virtually all infants with achondroplasia exhibit variably severe hypotonia in infancy. This hypotonia contributes to delays in motor development and risks for sudden death. Some have proposed that this hypotonia is a direct result of impaired function of long tracts of the spinal cord, secondary to the intrinsic narrowing of the foramen magnum, which also is present in variable severity in all children with achondroplasia. We postulated that if foraminal constriction causes infantile hypotonia, then there should be a strongly positive correlation between foraminal size and severity of hypotonia. Therefore, clinical and computed tomographic data in 71 infants were retrospectively reviewed. We found no correlation. These results suggest that there is no direct relationship and foraminal size does not affect severity of hypotonia. Other potential explanations for this infantile hypotonia are considered.

Mild hypophosphatasia mimicking severe osteogenesis imperfecta in utero: bent but not broken.

We describe a fifth instance of hypophosphatasia presenting with prenatal findings suggestive of a very severe bone dysplasia but with a subsequently benign course. Spontaneous improvement of long-bone angulation began prenatally. The postnatal course has been encouraging. This sixth clinical form of hypophosphatasia, which we suggest should be called the benign prenatal form of hypophosphatasia, should be added to the differential diagnostic possibilities considered when angulation or bowing of long bones is discovered prenatally.

Jugular bulb dehiscence in achondroplasia.

Jugular bulb dehiscence--complete absence of a roof over the jugular bulb--is a rare malformation, probably present in <<< 1% of the general pediatric population. Of 126 children with achondroplasia evaluated in the Midwest Regional Bone Dysplasia Clinic, four and probably five, were identified as having such dehiscence (at least 3.2% of the children assessed). Identifying this increased incidence in achondroplasia is of some clinical relevance, particularly including risk of difficult to control bleeding at myringotomy. It may also present as otherwise unexplained hearing loss, tinnitus and self audible bruits in these children.

Errors in the prenatal diagnosis of children with achondroplasia.

To provide data about the frequency of prenatal misdiagnosis in achondroplasia (Ach), we retrospectively abstracted data from 37 consecutive referrals of infants with Ach where ultrasound was performed prenatally. Nine of 37 (24 per cent) had a positive family history of Ach; all nine were correctly diagnosed prenatally. Of the 28 with no family history of Ach, 16 (57 per cent) were recognized to have abnormalities on ultrasound but none was given a definite diagnosis of Ach. Five families received an appropriate diagnosis of "most likely' Ach and four others were given a non-specific (but appropriate) diagnosis of some dwarfing disorder, not otherwise specified. In seven instances (25 per cent), an incorrect diagnosis of a lethal or very severe disorder was provided. These results illustrate the difficulty of making a specific prenatal diagnosis of Ach. In the face of the resulting uncertainty, physicians appear to elect to emphasize the most severe of alternative diagnoses. Given the homogeneity of mutations within the fibroblast growth factor receptor 3 (FGFR3) gene in the vast majority of patients with Ach, FGFR3 mutational analysis can be offered in every instance where a short-limb disorder is ultrasonographically detected in the latter stages of pregnancy. This would reduce the amount of incorrect and potentially harmful information provided to families.