What is the Difference Between Achondroplasia and Pseudoachondroplasia

The key difference between achondroplasia and pseudoachondroplasia is that achondroplasia is an inherited bone growth disorder due to mutations in the FGFR3 gene, while pseudoachondroplasia is an inherited bone growth disorder due to mutations in the COMP gene.

Inherited bone disorders cause bone problems due to genetic mutations. Some examples may include osteogenesis imperfect, neurofibromatosis, Hurler and Marfan syndrome, Gaucher’s disease, achondroplasia, pseudoachondroplasia, etc. Therefore, achondroplasia and pseudoachondroplasia are two different inherited bone growth diseases.

CONTENTS

1. Overview and Key Difference
2. What is Achondroplasia 
3. What is Pseudoachondroplasia
4. Similarities – Achondroplasia and Pseudoachondroplasia
5. Achondroplasia vs. Pseudoachondroplasia in Tabular Form
6. Summary – Achondroplasia vs Pseudoachondroplasia

What is Achondroplasia?

Achondroplasia is a hereditary condition that results in the restricted growth of long bones due to the ossification of cartilage. This ultimately leads to very short limbs and a face that is small in size in comparison to the skull. Achondroplasia mainly occurs due to the mutation in the FGFR3 gene. In fact, it is the most common form of short stature, characterized by adults who are shorter than 4 feet 10 inches in height. Approximately 1 in 15,000 to 1 in 40,000 individuals are born with this condition. Moreover, the symptoms of achondroplasia may include shortened bones (thigh or upper arm), short hands and feet, a large separation between third and fourth fingers, maximum height of less than 4 feet, larger head than normal size, prominent forehead, flat nose, and delayed development in infants. The complications resulting from this condition include back and leg pain, breathing problems, obesity, recurring ear infections, curved spine, bowed legs, hydrocephalus, and obstructive sleep apnea.

Achondroplasia can be diagnosed through ultrasound, X-ray, MRI, CT scan, physical examination, prenatal examination, and genetic testing. Furthermore, there is no cure for achondroplasia. Still, it can be managed by weight management, surgery to decrease fluid pressure on the brain, surgery to remove adenoids and tonsils, growth hormones, use of continuous positive airway pressure (CPAP), nasal mask for apnea issues, antibiotics to prevent ear infections, support in socialization, and taking medications that might help in increasing height by a few inches.

What is Pseudoachondroplasia?

Pseudoachondroplasia is an inherited short-limbed dwarfing condition. It was first described in 1959 by Drs. Maroteaux and Lamy. It is usually recognized in patients aged between 2 and 4 years. The symptoms of this condition may include normal height at birth followed by a decrease in height by age 2, short extremities, windswept deformity, and premature arthritis in the hips, knees, and ankles. However, this condition is characterized by typical facial features, head size, and intelligence. The complications of pseudoachondroplasia include osteoarthritis, cervical instability, kyphosis, scoliosis, and hip subluxation.

Pseudoachondroplasia is diagnosed through medical history, physical examination, X-rays of the neck, spine, lower extremities, pelvis, and arthrograms. Furthermore, pseudoachondroplasia is treated through social support, cervical fusion with the placement of a halo for instability, posterior spinal fusion for kyphosis, scoliosis, pelvic osteotomies for hip problems, lower extremity osteotomies for lower leg deformities, and total joint replacement in the hips and knees.

What are the Similarities Between Achondroplasia and Pseudoachondroplasia?

• Achondroplasia and pseudoachondroplasia are two different inherited bone growth diseases.
• Both conditions are present since childhood.
• Individuals suffering from both conditions have normal intelligence.
• Shorter extremities characterize both conditions.
• They can be diagnosed through medical history, physical examination, X-ray, and MRI.
• They can be managed up to some extent by surgeries.

What is the Difference Between Achondroplasia and Pseudoachondroplasia?

Achondroplasia is an inherited bone growth disorder due to a mutation in a gene called FGFR3. At the same time, pseudoachondroplasia is an inherited bone growth disorder due to a mutation in a gene called COMP. Thus, this is the key difference between achondroplasia and pseudoachondroplasia. Furthermore, achondroplasia is characterized by abnormal facial features and head size, while regular facial features and head size characterize pseudoachondroplasia.

The infographic below presents the differences between achondroplasia and pseudoachondroplasia in tabular form for side-by-side comparison.

Summary – Achondroplasia vs Pseudoachondroplasia

Many diseases of the skeletal system or bones are congenital, i.e., they become evident soon after birth. Achondroplasia and pseudoachondroplasia are two different inherited bone growth diseases present since childhood. Both these conditions are characterized by short extremities. However, they are developed due to different genetic mutations. Achondroplasia is developed due to the mutation in the FGFR3 gene, while pseudoachondroplasia is developed due to the mutation in the COMP gene. So, this is the key difference between achondroplasia and pseudoachondroplasia.

Reference:

1. “Achondroplasia.” MedlinePlus.
2. “Pseudoachondroplasia – Symptoms, Causes, Treatment: Nord.” National Organization for Rare Disorders.

Image Courtesy:

1. “Hands of a girl with achondroplasia Wellcome L0062546” By Welcome Images (CC BY 4.0) via Commons Wikimedia
2. “Pseudoachondroplasia. 02a” By Bonejoint – Own work (CC BY-SA 4.0) via Commons Wikimedia