Achondroplasia: Types, Causes, Symptoms, Treatment- CPAP, Suboccipital Decompression

Achondroplasia is a bone growth disorder. Achondroplasia is the most common type of disproportionate short stature.¹ Achondroplasia is a condition found in one in every 15,000 to one in every 40,000 children. Achondroplasia is a condition that usually occurs due to gene alteration or mutation in the Fibroblast Growth Factor Receptor 3 gene. The FGFR3 gene gives birth to a protein known as Fibroblast Growth Factor Receptor 3 that is responsible for converting cartilage to bone. FGFR3 is the one and only gene associated with achondroplasia. Achondroplasia affects children having only a single copy of the normal FGFR3 gene and a single copy of the FGFR3 gene mutation.

Achondroplasia literally means without cartilage formation, but in actuality achondroplasia is a condition, which does not affect the cartilage formation in any way. The actual problem in achondroplasia is the conversion of the cartilage to the bone, specifically the long bones of the body, which does not take place.

Most of the cases of achondroplasia consist of average-size parents where the FGFR3 gene mutation is caused in one of the parent’s sperm cell or egg before conception. In some cases the child inherits the disorder from a parent who already has achondroplasia.

Achondroplasia is an inherited disorder that leads to abnormally short stature associated with disproportionately short limbs. Achondroplasia is a condition in which the average height of an adult is recorded as 52 inches or 4 foot 4 inches in males and 49 inches or 4 foot 1 inch in females.

Children suffering with achondroplasia have to be monitored carefully and given good support for adjusting socially.

Given Below Are Few Common Types of Achondroplasia:

• Pseudo-Achondroplasia: Although the appearance of face is normal, the child may develop irregular growth plates in the knees and hips.²
• Hypochondroplasia: Hypochondroplasia is a condition, which affects the child less severely. The height of the child is over 54 inches excluding spinal stenosis.

Achondroplasia is one of the oldest recognized birth defects. Approximately 1 in 25,000 births worldwide get affected with achondroplasia. Achondroplasia has been seen equally in all the races and in both males and females.

Compression of the spinal cord and/or upper airway obstruction increases the risk of death in infancy.

• Achondroplasia is referred to as a genetic disorder. Achondroplasia is caused when certain directive genes of the body start performing improperly. This leads to the abnormal functioning of the fibroblast growth factor receptor i.e. proteins in the body. This often results in slowing down the growth of the bones that happens in the cartilage of the growth plate resulting in shorter stature, shorter bones and abnormally shaped bones.
• Achondroplasia is also caused due to genetic defect that passes from a parent to a child due to spontaneous mutation occurring in the growing embryo.

• Short stature.
• Prominent forehead.
• Abridged legs and arms.
• Bowed legs.
• Reduced muscle tone.
• Disproportionately large size of the head when compared to the rest of the body.
• Spinal stenosis.
• Individuals suffering with achondroplasia may have breathing problems such as apnea.
• Persistent gap between the ring and long fingers resulting in abnormal appearance of the hand.
• Spine curvatures such as lordosis and kyphosis.
• Misaligned and crowded teeth.
• Broad and short flat feet.
• Infection in the middle ear is often seen.
• Normal intelligence.
• The problem in the lower back causes back pain that creates difficulty while walking.
• Obesity.
• Delay in achieving developmental milestones.

• There is no particular cure available for treating achondroplasia. Special growth curves standardized for achondroplasia help in monitoring height, weight and head circumference of the children born with the disorder. There may be other secondary physical abnormalities that may be seen in patients due to achondroplasia such as breathing problems or spinal disorders and these need to be treated accordingly.
• An MRI and CT scan may be required for future evaluation of signs of spinal cord compression and severe muscle weakness. Different ways and measures of keeping weight under control are recommended beginning in the early age itself.
• Breathing problems that arise due to achondroplasia may need to be treated accordingly such as with CPAP through nasal mask, a surgical opening in the airway i.e. tracheostomy or surgical removal of the adenoids and tonsils that may help in correction of the obstructive sleep apnea.
• Suboccipital decompression if required is done to reduce pressure on the brain in case of problems related to the lower limbs like clonus, central hypopnea and hyperreflexia.

A complete subjective and objective examination is performed to diagnose achondroplasia.

• Genetic testing in order to investigate for FGFR3 gene mutation.
• X-rays may aid further in the diagnosis.

References: