This, in the end leads to he disturbances in bone growth which are the characteristics of this disorder. Individuals living with the condition are known to have a completely normal life expectancy. In simpler terms, hypochondroplasia is a genetic form of short stature, which belongs toa class of dwarfism. This is a result of a problem with bone formation or growth. Individuals with hypochondroplasia show a disproportion in arms and legs, being shorter than the average size. Only 70% of hypochondroplasia cases are caused by the mutation of the FGFR3 gene.
It is believed that the other 30% of remaining cases are caused by the ndividual having another FGFR3 gene, which is inherited in an autosomal dominant manner. There is a 50% chance that a person with this condition will pass it on to each with 2 altered copies of the FGFR3 gene (meaning both parents are affected), they tend to have more severe problems with bone growth then a child would if it were born with Just 1 FGFR3 mutation. However, a child can be born with hypochondroplasia to average size parents. This happens due to a new chance change (mutation), meaning that the risk of this happening again is virtually zero.
Hypochondroplasia, is Just one of many in a family of bone dysplasias which are aused by the same mutation in the FGFR3 gene. Some examples of other conditions in this family are, achondroplasia (which is the closest to hypochondroplasia but more severe), SADDAN syndrome, and thanatophoric dysplasia. Hypochondroplasia however, is known to be the mildest in this particular series of related conditions. Common features of one with hypochondroplasia are, short arms, short legs, broad, short hands and feet, large head, limited range of motion at the elbows, sway of the lower back, and bowed legs.
It is estimated that 1 in every 15,000 to 40,000 newborns are born with hypochondroplasia each year, in the USA alone. This works out to only 0. 01% of the population. One site reports that there are approximately 180,000 to 312,000 known live births, to date. Health Conditions Associated With Hypochondroplasia GROWTH An individual with hypochondroplasia, will reach a total adult height of 3’10” to 5’5″ (118-165cm). The median height for people with this condition is usually 48″. Sometimes the diagnosis of this condition can be delayed due to growth being so close to normal, in the first 3 years of life.
Parents should pay close attention to the other health conditions associated with this condition, in order to catch the diagnosis arly enough so that they can deal with the potential problems to come. Some may choose to use a growth hormone however; this has a very minimal effect, if any. HEAD GROWTH About 50% of children with hypochondroplasia also have macrocephaly, meaning their head is abnormally large. This condition is diagnosed when the circumference of the child’s head is more than two times the average size for children of their same age, race, sex, and period of gestation.
Regular neuroimaging should be done if the growth of the child head accelerates or if signs and symptoms of hydrocephalus (which is caused by the buildup of erebrospinal fluid) occur. In some more severe cases, ventriculoperitoneal shunting is performed. Signs and symptoms to watch for when determining if one has hydrocephalus are, abnormal gait, urinary incontinence, and dementia. Seizures are evident in only a small number of hypochondroplasia cases, this being number being near 5-10%. However, in almost all of these cases individuals also have temporal lobe dysgenesis, which is a structural abnormality of the brain.
The standard treatments used for individuals with epilepsy can be used by those with hypochondroplasia, for the treatment of seizures. Health Conditions Associated with Hypochondroplasia (Cont’d) DEVELOPMENT Near half of individuals with hypochondroplasia are diagnosed with a learning disability, 10-12% of these individuals have a secondary diagnosis of mental retardation. Special programing and teachers directed to an individual’s specific needs are available for those who require the assistance.