The key difference between achondroplasia and hypochondroplasia is that achondroplasia is a genetic disorder characterized by severe shortness and body disproportion, while hypochondroplasia is a genetic disorder characterized by milder shortness and body disproportion.
Dwarfism occurs when an individual is extremely short. In humans, individuals who have a height less than 147cm suffer from dwarfism. Dwarfism can be due to genetic mutation or growth hormone deficiency. We can categorize dwarfism into two categories: disproportionate dwarfism and proportionate dwarfism. Disproportionate dwarfism is characterized by either short limbs or a short torso, while in proportionate dwarfism, both the limbs and torso are unusually small. Achondroplasia and hypochondroplasia are two types of genetic disorders that show disproportionate dwarfism.
CONTENTS
1. Overview and Key Difference
2. What is Achondroplasia
3. What is Hypochondroplasia
4. Similarities Between Achondroplasia and Hypochondroplasia
5. Achondroplasia vs Hypochondroplasia in Tabular Form
6. Summary
What is Achondroplasia?
Achondroplasia is a genetic disorder characterized by severe shortness and body disproportion. It is an inherited genetic disorder whose main feature is dwarfism. It is a result of p.Tyr278Cys. and p.Ser348Cys mutations of the FGFR3 gene. This causes the protein of the FGFR3 gene to be overactive. It follows an autosomal dominant inheritance pattern. About 80% of cases result from a new mutation. Moreover, the risk of new mutations increases with the age of the father. Those affected have a height of 118-145 cm for males and 112-136 cm for females. The other significant features are the enlarged head, prominent forehead, shortening of proximal legs, short fingers and toes, trident hands, small midface, flattened nasal bridge, spinal kyphosis, lordosis, bowleg, knock knee, sleep apnoea, and frequent ear infection. This disorder generally does not affect intelligence. Achondroplasia occurs in 1 in 20000 to 30000 live births.
Figure 01: Achondroplasia
Achondroplasia can be detected through a prenatal ultrasound. A DNA test can also be performed to detect the genetic mutation. There is no treatment for this condition. The most recommended treatments are support groups and treating complicated conditions such as obesity, hydrocephalus, obstructive sleep apnoea, middle ear infection, spinal kyphosis. Even though the human growth hormone is used for treatment, it does not help people with achondroplasia. The drug vosoritide shows promising results in stage 3 human trials for achondroplasia disorder. Furthermore, controversial limb-lengthening surgery can increase the length of legs and arms of people who suffer from this genetic disorder.
What is Hypochondroplasia?
Hypochondroplasia is a genetic disorder characterized by milder shortness and body disproportion. It results from p.Asn540Lys. mutation of FGFR3 gene. It also follows an autosomal dominant inheritance pattern. The height of the males with this disorder is 145 to 165 cm, while the height of the females with this disorder is 133 cm to 151 cm. The characteristic features are shorts arms and legs, limited range of motion at elbows, large head, lordosis, brachydactyly, micromelia, spinal stenosis, skeletal dysplasia, abnormality of the femur, etc. The incidence of hypochondroplasia occurs in 1 in 15000 to 40000 newborns.
Figure 02: Hypochondroplasia
The diagnosis of this disorder can be done through X-rays and additionally genetic testing for specific mutations. The treatment for hypochondroplasia usually includes orthopedic surgery, physical therapy, and genetic counselling for individuals and their families. People who have spinal stenosis can undergo laminectomy.
What are the Similarities Between Achondroplasia and Hypochondroplasia?
- Achondroplasia and hypochondroplasia arise due to different mutations in the FGFR3 gene.
- They are inherited genetic disorders.
- These follow autosomal dominant inheritance patterns.
- Both types of genetic disorders show disproportionate dwarfism.
- These disorders have a characterized short stature.
What is the Difference Between Achondroplasia and Hypochondroplasia?
Achondroplasia is a genetic disorder that accompanies severe shortness and body disproportion, while hypochondroplasia is a genetic disorder that accompanies milder shortness and body disproportion. This is the key difference between achondroplasia and hypochondroplasia. Achondroplasia generally does not affect intelligence, but hypochondroplasia may have mild mental retardation. This is another difference between achondroplasia and hypochondroplasia.
The below infographic lists the difference between achondroplasia and hypochondroplasia in tabular form.
Summary – Achondroplasia vs Hypochondroplasia
Dwarfism is a disorder characterized by shorter than normal skeletal growth. This disorder can be due to genetic or hormonal deficiency. Over 100 different conditions can cause dwarfism. Achondroplasia and hypochondroplasia are two types of genetic disorders that have disproportionate dwarfism. Achondroplasia is a genetic disorder that accompanies severe shortness and body disproportion, while hypochondroplasia is a genetic disorder that accompanies milder shortness and body disproportion. This is the key difference between achondroplasia and hypochondroplasia.
Reference:
1. Kivi, Rose. “Achondroplasia: Causes, Symptoms, and Diagnosis.” Healthline, Healthline Media.
2. “Hypochondroplasia.” Johns Hopkins Medicine.
Image Courtesy:
1. “Kyle Pacek” By Kyle Pacek – (CC BY-SA 3.0) via Commons Wikimedia
2. “Hypochondropl 17J W” By Kinderradiologie Olgahospital Klinikum Stuttgart – Own work (CC BY-SA 4.0) via Commons Wikimedia