Reports from the MHC-database
5:100 000 live births
Achondroplasia is caused by a mutation on chromosome 4. It is inherited as an autosomal dominant trait. A new change in the genetic code, a spontaneous mutation, is the cause of the syndrome in 80-90% of cases.
Achondroplasia is a disease of the skeleton that affects growth. Children with achondroplasia are born with short arms and legs. Achondroplasia is the most common type of diagnosis with a short stature and the mean length for men is 132 cm and for women 125 cm. The skull is larger than average. After the first few months, the baby’s growth slows down dramatically, and as early as by the age of 9 months, the child is seriously short for age. As he or she continues to grow, the arms and legs grow slowly, while trunk growth is closer to normal. Other characteristics include reduced muscle strength, joint laxity (particularly the knees), and difficulties in balancing the head. Due to a narrow spinal cord there is an increased risk for neurological symptoms such as pain, sensory loss or pricking sensation.
While skull growth is greater than average, the face does not keep pace. This is especially true of the mid-face, and may result in narrowing of the respiratory canals, which, in turn, increases the risk of snoring, ear infections and sleep apnea (cessation of breathing during sleep). Frequent ear infections may cause hearing impairment. The small size of the mid-face affects the upper jaw with growth impairment, which often results in a protruding jaw. The teeth are of normal size, but both upper and lower teeth may be crowded. An open frontal bite may also occur – a distance between the upper and lower front teeth may make it difficult to take bites prior to chewing.
- It is important that these children receive dental preventive treatment, with extra prophylactic care and information on oral hygiene from an early age.
- Regular check-ups of dental and jaw development. Orthodontist should be consulted when needed.
- In cases of severe malocclusion, orthodontic treatment in combination with craniofacial surgery may be needed in late adolescence.
- Problems associated with snoring and sleep apnea should be followed up by a physician.
- The rare diseases database of the Swedish National Board of Health and Welfare.
- The MHC database - The Mun-H-Center database on oral health and orofacial function in rare diseases.
- The Documentation from the Ågrenska national competence centre for rare diseases.