A Natural History Study in Children With a Type II Collagen Disorder With Short Stature

Inclusion Criteria: * Confirmed diagnosis of type II collagen disorder with short stature at birth (2 standard deviations (SD) or more below the mean) i.e., Hypochondrogenesis, Kniest, Spondyloepiphyseal dysplasia congenita (SEDc) Spondyloepimetaphyseal dysplasia (SEMD) Strudwick type, Spondyloperipheral dysplasia (SED). * Children up to and including 12 years of age, up to the day before their 13th birthday, on the date of consent/assent. * The patient is sufficiently able, in the opinion of the Investigator, to adhere to the study visit schedule and other protocol requirements. * The patient's parent(s) or legal guardian(s) has signed written informed consent, according to the local regulations and after all relevant aspects of the study have been explained and discussed. * The child (depending on local institutional review board/ethical committee requirements) has provided assent. Exclusion Criteria: * Tanner stage 3 or more based on investigator assessment during physical examination * The patient has a diagnosis of any short stature condition other than a type II collagen disorder. * The investigator and/or clinical study advisory committee considers the patient has a type II collagen disorder which is not Hypochondrogenesis, SEDc, Kniest, SEMD or SED i.e., Stickler. * The patient has any other medical condition that may impact growth or where the treatment is known to impact growth, such as but not limited to hypothyroidism or hyperthyroidism, insulin-requiring diabetes mellitus, autoimmune inflammatory disease, autonomic neuropathy or inflammatory bowel disease. * Treatment in the previous 12 months prior to consent/assent with growth hormones, insulin-like growth factor 1, anabolic steroids, or any other drug expected to affect growth velocity. Brief (up to a few weeks) use of steroids is permitted. * Participation in any interventional clinical trial or treatment for a type II collagenopathy. * Has any condition or circumstance that in the view of the investigator places the child at high risk of poor compliance with the visit schedule or of not completing the study.