Kniest dysplasia is a congenital developmental disorder of the skeleton that goes back to a genetic mutation and is characterized by severe short stature. The prognosis depends on the severity of the individual case. Causal therapies are not yet available.
What is Kniest dysplasia?
Because of the thickening of the bones and the largely immobile joints, some patients are affected by the complete inability to walk. Osteoporosis can also be an accompanying symptom of the disease. See AbbreviationFinder for abbreviations related to Kniest Dysplasia.
Spondylometaepiphyseal dysplasia manifests itself from about the second year of life in growth and associated gait disorders. One dysplasia from this group of diseases is Kniest dysplasia. The disease is also called Kniest syndrome and corresponds to a congenital developmental disorder of the skeletal bones. This severe skeletal dysplasia causes extreme short stature accompanied by characteristic skeletal changes.
The disease is counted among the collagen diseases. This group of diseases includes systemic diseases with a degeneration of the connective tissue, which is accompanied by a dysregulation in the immune system and the formation of autoantibodies against the body’s own structures. The frequency of Kniest dysplasia is not known. The first description goes back to the pediatrician Kniest, who documented the disease at the end of the 20th century. Kniest’s dysplasia has an extremely wide range of degrees of severity.
Kniest’s dysplasia is a genetic disease of which 200 cases have been documented to date. Familial accumulations have been observed in the previously documented cases. Inheritance can be autosomal dominant. However, most of the previous cases are new mutations. Type II collagens, which have secretion defects in patients with knee syndrome, have now been identified as the cause.
The defective collagens are due to mutations in the COL2A1 gene. Most of the mutations are structural defects that appear as in-frame mutations. The cause of the disease is a deletion or a splicing mutation in the gene that codes for type II collagen. Most cases of Kniest dysplasia correspond to a heterozygous de novo mutation of the COL2A1 gene. Patients with dysplasia have a 50 percent risk of passing the defect on to biological children.
Symptoms, Ailments & Signs
Patients with Kniest dysplasia can present with a variable spectrum of symptoms that affect prognosis. Clinically, Kniest’s syndrome impresses immediately after birth and is characterized in infancy by disproportionate short stature. The disproportionality is mainly caused by a shortening of the trunk.
Most patients reach an adult height between only 106 and 156 centimeters. In addition to kyphosis of the thorax, lumbar lordosis is often present. The patients’ short extremities further aggravate the disproportionate impression. In most cases, Kniest syndrome is also associated with distended joints. This relationship often worsens as the disease progresses.
A flat midface and a sunken bridge of the nose can also be other symptoms. Around half of all those affected also have a cleft palate. Deafness occurs just as often. A somewhat rarer symptom is myopia, i.e. nearsightedness of varying severity. In addition, there is often progressive dysplasia of the extremities and axial skeleton.
Because of the thickening of the bones and the largely immobile joints, some patients are affected by the complete inability to walk. Osteoporosis can also be an accompanying symptom of the disease.
Diagnosis & course of disease
X-ray findings are usually used to diagnose Kniest syndrome. In addition to deformed epiphyses, the radiographs provide evidence of missing femoral heads, enlarged femoral metaphyses, platyspondylia, and vertebral anomalies in those affected.
Histopathological findings can support the diagnosis by showing inclusions in the chondrocyte cytoplasm or an extremely vacuolated matrix of the cartilage. Special forms of spondyloepiphyseal dysplasia and metatropic dysplasia should be considered as differential diagnoses. Young patients with Kniest dysplasia in particular often have clinical and radiological findings that overlap with OSMED findings.
Myopia helps in the differential diagnosis to OSMED. If the worst comes to the worst, a molecular genetic analysis can confirm the diagnosis. If the dysplasia is known in the family, the mutation can also be diagnosed prenatally. Micromelia can be detected by ultrasound from the second trimester. The prognosis for patients with Kniest dysplasia depends on the severity of their joint and vertebral anomalies in the individual case. Depending on the severity, the prognosis can vary between a fatal and a favorable course.
Kniest dysplasia usually leads to significant limitations in everyday life and in the life of the affected person. The various malformations in the skeleton cause restricted movement and, in most cases, pain. The quality of life is greatly reduced by Kniest dysplasia. Furthermore, the patients also suffer from severe short stature.
This can lead to teasing or bullying, especially in children, and thus trigger severe mental health problems or depression. It is not uncommon for the parents and relatives of those affected to be affected by mental health problems, which can usually be treated by a psychologist.
The patient also suffers from short-sightedness and hearing problems. A cleft palate is also not uncommon and can limit the aesthetics of the affected person. The joints cannot be moved properly, which can lead to limitations in everyday life. The person concerned may be dependent on the help of other people.
Likewise, Kniest’s dysplasia can also disrupt the child’s mental development, leading to retardation. A causal treatment of Kniest dysplasia is usually not possible. The disease can only be treated symptomatically. Life expectancy is reduced by this disease in most cases.
When should you go to the doctor?
If symptoms such as hearing loss, short-sightedness or short stature occur, Kniest dysplasia may be the underlying cause. A doctor must be consulted if serious complaints occur that significantly affect well-being and quality of life. If the symptoms persist for more than a few days, medical advice is also required. The congenital form of Kniest dysplasia is usually diagnosed immediately after birth. Treatment is then initiated promptly and parents are advised to see the child regularly to a doctor.
If symptoms reappear after the initial treatment, the doctor responsible must be consulted. Signs of osteoporosis require clarification by a specialist. Kniest’s dysplasia often takes a severe course and represents a great psychological burden for the child and the parents. For this reason, therapeutic advice should always take place alongside the treatment of the deformities and physical complaints. The family doctor or orthopedist can put you in touch with a specialist and, if necessary, put the affected family in touch with a self-help group.
Treatment & Therapy
There is no causal therapy available for patients with Kniest dysplasia. Those affected can only be treated supportively. The goal of therapy is to maintain patient mobility. Surgical intervention may be part of the symptomatic treatment designed for this purpose. For example, if a hip dislocation is suspected in the near future, this dislocation can sometimes be averted by surgical intervention.
During the growth phase, other neurological deficits can occur in addition to myopia. Not only the motor, but also the mental development of the patient can be retarded in this way or, in the worst case, even stopped. For this reason, close monitoring by a neurologist during the growth phase is recommended. In the case of flexions or displacements of the bones that are more than five millimeters, stabilization must be carried out.
This stabilization usually corresponds to an operative intervention by a surgeon. If signs of retinal detachment are detected, surgical repair is usually done as well. Supportive therapy for dysplasia can extend to the parents of the affected person, who can receive therapeutic care or genetic counseling, for example.
Outlook & Forecast
As a parent of a child suffering from Kniest dysplasia, you can take action yourself to improve the quality of life for the child. Even before the birth, parents can seek psychotherapeutic help in order to better process and accept the new situation. Contact with other affected families, for example through self-help groups, has proved positive. You get a good overview of what to expect in the future and receive valuable advice for problems in everyday life.
Appropriate medical treatment must be provided immediately after the birth. For this purpose, it is necessary to consult a specialist doctor at an early stage and have any necessary operations carried out. After the wounds have healed, it can be clarified with the doctor when physiotherapeutic treatment can be started. The earlier such therapy begins, the better the chances of maintaining existing mobility. Nevertheless, it is advisable to redesign the living environment to be handicapped accessible or to plan a move to an apartment that is handicapped accessible. If the child later needs a walking aid or a wheelchair, a solution does not have to be found under time pressure.
Regular check-ups by a neurologist reveal bone displacements that require immediate stabilization. Other neurological deficits can also be identified quickly. This makes it possible to slow them down or even stop them.
The primary causes of themutationof the causative gene are not yet known in Kniest dysplasia. For this reason, hardly any preventive measures are available. In family planning, however, potential parents can at least have their genetic risk for offspring with dysplasia assessed.
In most cases, the options for aftercare for Kniest’s dysplasia are severely limited, with the focus on this disease being rapid and, above all, early detection of the disease. Ideally, the person affected should consult a doctor as soon as the first signs and symptoms of the disease appear, so that the symptoms do not worsen further.
In most cases, those affected are dependent on the help and care of other people in their everyday lives. The support of one’s own family in particular has a very positive effect on the further course of the disease. Loving and intensive conversations are also very helpful and can prevent the development of depression or other mental upsets.
Since this disease can also have a negative effect on the eyes of those affected, an operation should definitely take place if the retina is detached. After such an operation, the eyes should be particularly well filled and cared for. If you wish to have children, a genetic examination and counseling can be carried out first, so that Kniest dysplasia cannot occur again in the descendants.
You can do that yourself
People suffering from Kniest dysplasia require comprehensive care from doctors and therapists.
Parents of affected children should seek support at an early stage and arrange any operations as soon as possible. Good preparation gives the parents the necessary freedom after the birth to process the illness of their own child first. However, therapeutic help is usually useful, because Kniest’s dysplasia will burden the parents for many years and cause stress that has to be dealt with. In addition, measures must be taken to enable the child to lead a life with as few complications as possible. The apartment usually has to be set up to be handicapped accessible, and aids such as walking aids, a wheelchair or visual aids must also be usedget organized. After a comprehensive examination, the doctor can make a good assessment of the subsequent symptoms to be expected.
The affected child should also receive psychological support at the latest in adolescence. Otherwise, the serious mental and physical limitations can lead to the development of mental illness. Preventive therapy is definitely necessary to avoid complications of this type. Close medical monitoring is always necessary for Kniest dysplasia.