Distinctive Skeletal Phenotype in Patients with Kniest Dysplasia

Background: A group of children presented with diverse forms of spine and joint pathologies in correlation with heritable bone disorders.

Patients and Methods: Five children aged from 9 -13 years, presented with a constellation of growth retardation, craniofacial dysmorphic features, axial (scoliotic short and barrel chested with marked diminution of spine biomechanics) and painful enlarged joints and sometimes with the propensity to develop mal-alignment (knock knees). We included a 38-years-old-lady, a mother of an affected boy because of her long term history of joint pain and intractable tinnitus. Clinical and radiographic phenotypic characterizations were the first line tools applied. 

Results: The clinical and radiographic phenotypes of all five children were consistent with the diagnosis of Kniest dysplasia. Strikingly, the reason behind the tinnitus in the short statured 38-years-old- lady was due to congenital hypoplasia of the posterior arch of the atlas (the hypoplastic posterior arch of the atlas was in connection with the developmental failure of chondrogenesis). Two children underwent the genetic testing and showed a genetic defect of encoding type II collagen (COL2A1).

Conclusion: Sadly speaking, soon after birth the vast majority of children born with skeletal dysplasia received the misdiagnosis of achondroplasia by their pediatricians and geneticists. In practice, a misdiagnosis can lead to hazardous repercussions for the affected children and their families. Correctly interpreting the clinical and the radiological phenotypes and relating them to etiologies is an essential basis for the proper management. In the field of hereditary bone disorders, the existence of mild and moderate forms of the same disease within other family subjects is a well-known fact (as seen in a 38-years-old- short statured- lady, a mother of an affected boy with Kniest dysplsia). To counter the overlooked maldevelopment of the atlanto-axial effectively, we need to delineate the disrupted anatomical structures of the craniocervical junction as early as possible. It is important to understand that many of these diseases are so mysterious and daunting that they frighten even some practitioners. Therefore, educating physicians is a priority.