Hypochondroplasia
| Classification according to ICD-10 | |
|---|---|
| Q77.4 | Achondroplasia hypochondroplasia |
| ICD-10 online (WHO version 2019) | |
The hypochondroplasia (HCH) is a form of disproportionated dwarfism . It is caused by a genetic change that slows down the growth of long bones . The symptoms are similar to those of achondroplasia , but less pronounced.
frequency
It is estimated that hypochondroplasia occurs in one in 30,000 newborns. This makes it one of the rare diseases . The frequency cannot be clearly determined, since hypochondroplasia is difficult to differentiate from constitutional short stature in less pronounced cases.
Symptoms
General symptoms
In people with hypochondroplasia, the arms and legs are shortened in relation to the trunk. However, this is far less noticeable than with achondroplasia . Otherwise, the symptoms are similar to those of achondroplasia, but they are milder. Often there is a hyperlordosis and a misalignment of the legs (usually bow legs). The hands are usually wide with short fingers. In many cases the elbow cannot be fully extended, but the knees and wrists can be hyperextended. Children in the first few years of life usually have slight muscle hypotonia , but this usually does not play a major role in motor development.
People with hypochondroplasia grow to be approximately 130 to 155 cm tall as adults.
Possible complications
Sometimes it is necessary to correct the leg deformity with an operation. Chronic otitis media sometimes develop in children with hypochondroplasia due to the reduced base of the skull.
In rare cases, the occipital opening in affected small children is so narrow that it has to be surgically widened if the resulting pressure on the spinal cord causes neurological failures and apneas . Spinal canal stenosis occurring in adulthood due to the narrowed spinal canal in connection with a strong lordosis of the lumbar spine is also rare .
root cause
Point mutations on the FGF R3 gene can be detected in almost 70% of patients who are diagnosed with hypochondroplasia based on the symptoms . Since this is not the case with the other patients, it is assumed that there is another, very similar short stature with an unknown cause.
The FGFR3 gene is located on chromosome 4 , gene locus 4p16.3. It regulates the growth of cartilage cells. Changes in this gene lead to an inhibition of cartilage development in the growth plates , as a result of which the long bones , which are mainly responsible for length growth, grow more slowly.
Hypochondroplasia is inherited in an autosomal dominant manner, which means that it can only be passed on by those who are affected by it. In all other cases the mutation of the FGFR3 gene occurs spontaneously when the embryo is formed; the short stature arises regardless of the size of the parents. The most common point mutations are C (1659) A and C (1659) G. Both mutations lead in the FGFR3 protein to an amino acid exchange at position 540 from asparagine to lysine.
diagnosis
The size of children with hypochondroplasia at the time of birth is still within the normal range, and the growth is only slightly disproportionate so that the short stature is not noticeable. Affected children only gradually fall behind their peers in growth; the arms and legs appear shortened in relation to the trunk and the gait pattern appears unusual. Therefore, the diagnosis is usually only made after learning to walk, sometimes much later.
As part of the diagnosis, other causes of short stature are usually ruled out first through blood tests, and the left hand is x-rayed to determine the age of the bone. The diagnosis of hypochondroplasia is then made on the basis of the growth process and any further X-rays of the legs and spine; the FGFR3 gene is often analyzed.
Dealing with the disability
Social aspects
Like other short people, people with hypochondroplasia stand out in public as unusual and are often stared at or not perceived by their counterparts as equal interaction partners. Small children are often exposed to teasing and bullying. The way parents deal with their child's disability therefore plays a major role, because if the child feels accepted in the family regardless of his or her height, this strengthens his self-esteem and his ability to assert himself against teasing. Overprotection and underchallenge, on the other hand, can weaken the child's self-confidence.
Despite these potential problems, many short people lead happy and contented lives.
Medical treatment
observation
When treating hypochondroplasia, the most important thing is to identify possible complications such as spinal stenosis at an early stage. Affected children should be neurologically examined during routine examinations to rule out spinal cord sprains. Furthermore, the parents of these children should be asked about signs of breathing disorders during sleep and the development of misalignments of the legs should be checked. The growth development of children and adolescents with hypochondroplasia should be monitored using a growth curve appropriate for achondroplasia.
renewal
Orthopedic lengthening of the arms and legs in childhood or adolescence is possible, but it is very tedious and often associated with severe pain. In German-speaking countries, limb extensions are rarely made.
Web links
- Hypochondroplasia. In: Online Mendelian Inheritance in Man . (English)
Individual evidence
- ^ Karl-Heinz Klingebiel: The work of the BKMF as a family-oriented health self-help . In: Mohnike, Klingebiel, Vaupel, Zabel (eds.): Achondroplasia and Hypochondroplasia . 2nd Edition. ABW Wissenschaftsverlag, 2013, ISBN 978-3-940615-41-1 , p. 151 .
- ↑ a b c Klaus Mohnike, Nora Vaupel: Clinical spectrum of achondroplasia and hypochondroplasia . In: Mohnike, Klingebiel, Vaupel, Zabel (eds.): Achondroplasia and Hypochondroplasia . 2nd Edition. ABW Wissenschaftsverlag, 2013, ISBN 978-3-940615-41-1 , p. 30-33 .
- ^ Johannes Correll, Johanna K. Correll: Achondroplasia and Hypochondroplasia - their pediatric orthopedic and orthopedic treatment . In: Mohnike, Klingebiel, Vaupel, Zabel (eds.): Achondroplasia and Hypochondroplasia . 2nd Edition. ABW Wissenschaftsverlag, 2013, ISBN 978-3-940615-41-1 , p. 80 .
- ↑ Bernhard Zabel: FGFR3 mutations as the cause of skeletal dysplasia of the achondroplasia group - elucidation of the disturbed signaling pathways in the growth plate . In: Mohnike, Klingebiel, Vaupel, Zabel (eds.): Achondroplasia and Hypochondroplasia . 2nd Edition. ABW Wissenschaftsverlag, 2013, ISBN 978-3-940615-41-1 , p. 3-10 .
- ↑ a b Bober, Bellus, Nikkel, Tiller: Hypochondroplasia . 2013, PMID 20301650
- ↑ Markus Bettendorf: Short stature in children and adolescents - Current aspects of diagnosis and therapy . 1st edition. UNI-MED, Bremen 2009, ISBN 978-3-8374-2067-8 , p. 40-43 .
- ^ Archives of the BKMF: Small stature from a psychosocial point of view . In: Mohnike, Klingebiel, Vaupel, Zabel (eds.): Achondroplasia and Hypochondroplasia . 2nd Edition. ABW Wissenschaftsverlag, 2013, ISBN 978-3-940615-41-1 , p. 143-150 .
- ^ Johannes Correll, Johanna K. Correll: Achondroplasia and Hypochondroplasia - their pediatric orthopedic and orthopedic treatment . In: Mohnike, Klingebiel, Vaupel, Zabel (eds.): Achondroplasia and Hypochondroplasia . 2nd Edition. ABW Wissenschaftsverlag, 2013, ISBN 978-3-940615-41-1 , p. 76-78 .
