Achondroplasia is the most common form of hereditary dwarfism. It causes disorders of cartilage and bone growth. There is a normal life expectancy.

What is Achondroplasia?

Achondroplasia is the most common form of hereditary dwarfism. The defect is inherited autosomal dominant. So that means that one gene is enough for the onset of the disease.

Achondroplasia is the classical form of dwarfism. At about 20, 000 births comes a child with achondroplasia. The disease is genetic and occurs in 80 percent of cases sporadically. In the other 20 percent is an autosomal dominant inheritance. Thus, the short stature is passed on to 50 percent, if one parent is affected. A fetus homozygous with the defective gene is not viable.

In new mutations, the probability of the occurrence of achondroplasia in the offspring correlates with the age of the father. The intelligence and life expectancy of those affected are normal. The growth is delayed after birth. The affected children are born with a normal size. By disrupting cartilage growth, the epiphysial junctions occlude too early.

At the same time, growth comes to a standstill. People with achondroplasia reach an average height of 120 to 130 centimeters. The affected women usually reach a height of 120 centimeters and men 130 centimeters.

causes

The cause of achondroplasia is a genetic defect in the fibroblast growth factor receptor gene (FGFR-3). In case of failure or defect of this gene, the receptor for the fibroblast growth factors becomes ineffective. These growth factors are responsible for normal fibroblast production. If its receptor is missing, it will disrupt the production of fibroblasts.

The defect is inherited autosomal dominant. So that means that one gene is enough for the onset of the disease. If the respective genes of both parents had the defect, the embryo would not be viable. The point mutation leading to achondroplasia is very well defined. Thus, in 97% of all cases in the coded protein at position 380, there is an exchange of glycine for arginine, whereas in the gene a GA exchange takes place (guanine to adenine).

In three percent of cases, there is a GC exchange (guanine to cytosine) at this point. In the encoded protein, however, the same amino acid exchange takes place.

Symptoms, complaints & signs

Achondroplasia is characterized by a variety of physical abnormalities. The main feature is the disproportionate dwarfism. Thighs and upper arms are shortened. The upper body shows a normal height. Striking are the short fingers, the enlarged skull with balcony front and the midface hypoplasia with flat nose root.

Midface hypoplasia is already recognizable at birth. Unlike the extremities, the trunk is long and narrow. Due to the too short extremities, short fingers, the big head and the too short neck the gross motor skills are learned only very slowly. Due to the hypoplasia of the midface and the almonds that are enlarged at the same time, the patient often suffers from obstructive sleep apnea. Very often there is a chronic otitis media, which can lead to hearing problems.

Even a teething condition often occurs. The upper portion of the spine is curved in the form of a kyphosis. The curvature occurs very early. At the same time there is also a hollow cross. Those affected often have O or X legs. Also striking are the hyperextension of the joints and the broad, short and dreizackförmigen hands. In early infancy or early childhood, respiratory arrest can sometimes occur due to spinal cord compression.

Furthermore, developmental delays and other long-term symptoms are attributable to this. In adulthood, spinal canal stenosis often leads to neurological problems. At the same time cardiovascular problems occur. A common problem is the occurrence of obesity. Pregnancies are possible, but the affected women have to be released due to the narrow pelvis by a Caesarean section.

Diagnosis & History

The diagnosis of achondroplasia is initially due to the external appearance. However, other forms of dwarfism must be excluded by differential diagnosis. The large head with balcony front and flat nose is very characteristic and serves as an important feature of demarcation. Furthermore, there are radiological examinations that detect typical changes in the skeleton. However, the diagnosis is finally confirmed by the molecular genetic analysis of the FGFR3 gene.

complications

As a possible complication of achondroplasia is in addition to an abnormal skull base and a midface hypoplasia to call. In the case of women, obesity problems can also present a problem in the context of obstetrics. In the course of the abnormal skull base, there may also be a narrow foramen occipitale magnum (constriction of the large occipital hole), which is associated with an increased intracranial pressure (increase in intracranial pressure).

Often, in the presence of this complication, a cervicomedullary compression is added, which in the best case occurs as cervical spine trauma, in its increased form also occurs with a cervical spinal cord injury. In some cases, a complication of a narrow occipital foramen may result in central apnea (respiratory failure).

If midface hypoplasia (reduction of the midface) occurs, it may cause dental developmental problems, deafness, the appearance of otitis media (otitis media), speech problems and relative swelling of the tonsils (tonsils). Further complications of achondroplasia are spinal canal stenoses, ie narrowing in the area of ​​the spinal canal.

As a result, sensory disturbances in the legs may develop and, in the worst case, paresis (paralysis) of the legs may occur. Also, disorders in the bladder and rectum can develop. In the knee area, achonroplasia can cause instability of the knee ligaments. As a psychosocial complication, in addition to the manifestation of depression, reduced self-esteem and partnership issues can also occur.

When should you go to the doctor?

With Achondroplasie does not necessarily have to go to the doctor. Medical treatment is only required if physical or mental discomfort occurs. If, for example, recurrent middle ear infections occur due to the typically narrowed Eustachian tube, this must be treated surgically. Even physical malformations such as O-legs or X-legs require treatment only in case of health problems. Often, young adults suffer from back pain, knee and hip pain, and middle ear and sinusitis.

These conditions must be diagnosed and treated by a specialist. Rarely, paralysis and dysfunction of the fingers and toes occur. As soon as the achondroplasia causes symptoms of this kind, a doctor must also be consulted. Further contacts are chiropractors, neurologists and orthopedists.

If dwarfism causes psychological problems, a therapist can be consulted. Parents whose children are short-lived can also consult appropriate counseling centers and self-help groups in consultation with the pediatrician. Early management of achondroplasia can reduce mental as well as physical impairments in later life.

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Treatment & Therapy

The treatment of achondroplasia is symptomatic. Functional disabilities due to spinal anomalies and incipient paralysis can only be remedied by stabilizing surgical procedures on the spine. Infants often require decompression of the spine through surgery. Sometimes an attempt is made to perform an operative limb lengthening.

The constant otitis media also require continuous treatment. If obstructive sleep apnea is present, it may be useful to remove the tonsils and to aim for weight loss in the case of obesity. Surgical procedures may be used to treat leg malalignment, spinal curvature, and spinal canal narrowing.

Also important is the offer of psychological and social support. Due to the good treatability of the individual symptoms, the life expectancy is normal or only slightly reduced.

Outlook & Forecast

In most cases, life expectancy is unaffected by achondroplasia. However, malformations and growth disorders occur, which can limit the patient's life. For example, shortened fingers appear that make gripping difficult.

Likewise, those affected suffer from hearing problems and inflammation in the ears. In the worst case, it can also lead to complete hearing loss. The joints are often overstretched, which can be bizarre, especially for other people. This causes bullying and teasing in children. Furthermore, respiratory problems can also occur due to achondroplasia, so that in the worst case it can lead to respiratory arrest. The heart is also affected by the malformations and the patient is suffering from a delayed development.

Disorders of sensitivity and paralysis also appear in the course of the disease. These can restrict the movement of the patient, so that it may be dependent on the help of other people in everyday life. Often a psychological support is needed.

The treatment is usually only symptomatic and can relieve the symptoms. Many of the malformations and deformities can be corrected.

prevention

The inheritance of achondroplasia is autosomal dominant. Therefore, for the prophylaxis of the inheritance of the short stature a human genetic counseling makes sense. Because this form of dwarfism can only be inherited from one parent to the offspring. This is the case when the defective gene is passed on.

Affected families therefore have a 50 percent chance of suffering from achondroplasia. However, there is no preventive measure against a spontaneous occurrence of the disease.

aftercare

Achondroplasia patients require comprehensive follow-up care. The dwarfism can affect different regions of the body and sometimes has an impact on the mental health of those affected. The orthopedic surgeon will accordingly conduct a comprehensive examination to ensure that no further complaints occur.

With increasing age of the affected persons it can come to further restrictions in the area of ​​the spine, the joints and the bones, which must be recognized early. The aftercare should take place every three to six months, always depending on the patient's health and any concomitant symptoms. With a positive course of the disease, the follow-up checks can be gradually reduced.

Achondroplasia patients, however, require permanent medical support. Accordingly, aftercare generally focuses on ensuring that the wounds heal well and that there are no problems moving the affected parts of the body after surgery. Above all, function or mobility of the affected body parts must be checked.

With the involvement of the organs regular ultrasound examinations are recommended. Since the achondroplasia can have very different characteristics, the aftercare varies considerably from patient to patient. Patients should strictly adhere to the guidelines of the doctor, so that in the long term, an improvement of the symptoms can be achieved.

You can do that yourself

Although genetic achondroplasia is a very rare hereditary disease, it accounts for the largest proportion of the small group. Since the dwarfism can already be detected in newborns, children are confronted with their otherness quite early. Self-help measures that could influence the course of the disease are not known.

In order to bring the children into everyday life in the best possible way, it is advisable for the parents to contact one of the self-help groups in which they can talk with other concerned parents and exchange their experiences with one another. One of the most important self-help measures for parents is to build a stable self-esteem in the children despite their short stature and possible other physical impairments. Last but not least, self-help groups also gain in importance for those affected as they grow older, because they can report on their own experiences and are confronted with the experiences of other children with achondroplasia.

Another important measure or task of the parents is to change home or apartment with small technical aids such as the installation of electric pull switches, cords on the doorknobs, low coat hooks and much more so that the affected child as early as possible allows a degree of independence, Likewise, care should be taken to ensure that the child wears a helmet during sporting activities such as skiing, cycling or skating in order to prevent the risk of injury.

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