Pathogenic single nucleotide variants (SNVs) found in the COL2A1 gene are associated with a broad range of skeletal dysplasias due to their impact on the structure and function of the Col2a1 protein. However, the molecular mechanisms of some nucleotide variants detected during diagnostic testing remain unclear. The interpretation of missense and splicing variants caused by SNVs poses a significant challenge for clinicians. In this work, we analyzed 22 splicing variants in the COL2A1 gene which have been found in patients with COL2A1-associated skeletal dysplasias. Using a minigene system, we investigated the impact of these SNVs on splicing and gained insights into their molecular mechanisms and genotype-phenotype correlations for each patient. The results of our study are very useful for improving the accuracy of diagnosis and the management of patients with skeletal dysplasias caused by SNVs in the COL2A1 gene.

BACKGROUND: Kniest dysplasia is a type of chondrodysplasia characterized by severe craniofacial abnormalities including tracheomalacia, midface hypoplasia, and cleft palate.
METHODS: We previously described a 6-year-old girl with Kniest dysplasia, in whom glottic edema rapidly developed after tracheal intubation. At the age of 13 years, a reoperation was scheduled to correct talipes equinovarus but was subsequently canceled due to failure of tracheal intubation and subsequent glottic edema. Airway evaluation by endoscopy and computed tomography 1 month later revealed severe laryngeal narrowing. Therefore, the second anesthesia was maintained with spinal anesthesia combined with sciatic nerve block without tracheal intubation.
CONCLUSIONS: Careful perioperative airway evaluation is required in patients with Kniest dysplasia, and alternative strategies for airway management other than tracheal intubation should be considered.

The purpose of this overview is to increase the awareness of clinicians regarding type II collagen disorders and their management. The following are the goals of this overview. GOAL 1: Describe the clinical characteristics of type II collagen disorders. GOAL 2: Provide an evaluation strategy to identify the genetic cause of a type II collagen disorder in a proband. GOAL 3: Inform genetic counseling of family members of an individual with a type II collagen disorder. GOAL 4: Review management of type II collagen disorders.

Kniest dysplasia is a type II collagen disorder that arises from a genetic mutation of the COL2A1 gene that results in short stature, midface anomalies, tracheomalacia, and hearing loss. Disruption of the normal collagen pathway can lead to many changes given its critical role in the body, and can cause complications with respect to wound healing. We present a case in which a patient with Kniest dysplasia successfully underwent multiple procedures in the head and neck region including cochlear implantation, mandibular distraction, palatoplasty, and laryngotracheal reconstruction. All procedures did not have any associated complications with respect to wound healing, indicating that surgery in this population can take place as indicated and surgery should not be contraindicated or delayed.

Constitutive COL2A1 mutations are associated with a wide variety of clinical manifestations known as type II collagenopathies. Among them is Kniest dysplasia, which is phenotypically variable and includes both skeletal (short trunk and limbs, kyphoscoliosis, prominent joints, and osteoarthritis) and craniofacial characteristics. Kniest dysplasia mutations primarily arise in the triple-helicoidal region of the alpha 1 (II) chain in COL2A1 between exons 12 and 24. Somatic COL2A1 mutations have been identified in chondrosarcoma, a rare cartilage forming neoplasm, with a hypermutability of the gene reported in 37% of cases. However, to the best of our knowledge, there is no reported increase in predisposition to chondrosarcoma in human collagenopathies, and no reported clinical association between these congenital diseases and cartilaginous tumors. In the case study presented here, we report the first description of an association between these two rare diseases involving COL2A1, in a child presenting with Kniest dysplasia and a grade I sphenoethmoidal chondrosarcoma. We also describe a new constitutive mutation in COL2A1.

BACKGROUND: The small bones and soft tissues of the hands and feet can be affected by systemic disorders, and frequently, the findings are quite unique and virtually diagnostic for some genetic or metabolic disorders.
METHODS: Photographs and imaging studies for the hands and feet are available in a digitized system, which has been approved by our hospital institutional review board. Examination of these and their description can establish a relationship with some degree of certainty to a series of highly variable and uncommon clinical disorders.
RESULTS: Description of the clinical, physiologic and genetic characteristics, and illustrations of hand and foot abnormalities are provided for an array of diseases, including Ellis-van Creveld syndrome, fibrodysplasia ossificans progressiva, achondroplasia, Kniest dysplasia, pseudo- and pseudo-pseudohypoparathyroidism, acromegaly, nail-patella syndrome, Marfan\'s disease, cartilage-hair hypoplasia, and several forms of mucopolysaccharidosis.
CONCLUSIONS: The findings support the concept that many genetic disorders can often be diagnosed by clinical and imaging examination of the patient\'s hands and feet.