Achondroplasia and Nutritional Concerns

Achondroplasia is the most common type of dwarfism - a genetic condition resulting in short stature, with a height of less than 4'10" at adulthood. One of the biggest nutritional concerns associated with achondroplasia is the predisposition to carry excess body weight, which can aggravate skeletal disorders. Although research indicates there are other genetic factors that likely impact weight status in this population, excessive weight gain often becomes a problem in mid-to-late childhood. Individuals with achondroplasia may also be prone to gastroesophageal reflux disease and obstructive sleep apnea.

For children, routine monitoring of weight and length or height are recommended using achondroplasia-specific growth charts. These include standard weight-by-height charts and those for assessing body mass index (BMI). Standard growth curves published in 1978 are still in existence and have been revisited by other researchers. They are not translatable as "ideal weight-for-height curves" and people with other types of dwarfism may have broader and heavier bones – limiting their application.

In 2017, anthropometric measures from 293 individuals with achondroplasia from birth to 16 years were analyzed using medical records. The study found that by 6 months of age, there was no overlap between the 95th percentile for stature of infants with achondroplasia and the 5th percentile of infants without achondroplasia. Earlier growth chart studies indicated a possible growth spurt during puberty among individuals with achondroplasia, however, recent reviews in both the United States and Argentina have not observed that same trend. Ongoing study is needed to identify what ideal healthy weight ranges may be and in observing differences between growth rates by age in different countries and geographical regions.

While research studies looking at achondroplasia in adults are also limited, one study from 2018 looked at the body composition, diet and energy expenditure of 33 Norwegian adults with achondroplasia. Energy expenditure was measured using indirect calorimetry and compared to both the Mifflin St Joer and Harris Benedict equations. The Mifflin St Joer equation significantly overestimated energy needs in both men and women, whereas the Harris-Benedict equation significantly overestimated energy needs in men with achondroplasia when compared to indirect calorimetry. Physical assessments suggested that a BMI between 25 and 29.9 kg/m2 may be regarded as typical for adults with achondroplasia; although no BMI standards have been established for individuals 17 and older with this condition.

Weight management and attention to overall calorie intake is typically a focus of care for many people with achondroplasia. However, individuals with achondroplasia face the additional challenge that they often must meet their nutrient needs while consuming fewer calories. The dietary analysis included in the Norwegian study found that low dietary fiber, iron, iodine, vitamin D and folate intake was a trend amongst individuals in this group, as was excess saturated fat intake. The intake of these dietary components is similar to those noted for various life stages in the Dietary Guidelines for Americans for the general population.

Whether working with adolescents or adults with achondroplasia, an individualized approach is needed in order to achieve adequate nutrition within calorie limits. Tools such as indirect calorimeters may be beneficial for determining energy needs, and population specific tools should be sought out as this continues to be an area of ongoing study.

References:

• Saint-Laurent C, Garde-Etayo L, Gouze E. Obesity in achondroplasia patients: from evidence to medical monitoring. Orphanet J Rare Dis. 2019 Nov 14;14(1):253.
• Legare JM. Achondroplasia. 1998 Oct 12 [Updated 2020 Aug 6]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews^®. Seattle (WA): University of Washington, Seattle; 1993-2021.
• Hoover-Fong J, Scott CI, Jones MC, AAP Committee on Genetics. Health Supervision for People with Achondroplasia. Pediatrics. 2020;1 45(6):e20201010.
• Hoover-Fong J, McGready J, Schulze K, Alade AY, Scott CI. A height-for-age growth reference for children with achondroplasia: Expanded applications and comparison with original reference data. Am J Med Genet A. 2017 May;173(5):1226-1230.
• Madsen A, Fredwall SO, Maanum G, Henriksen C, Slettahjell HB. Anthropometrics, diet, and resting energy expenditure in Norwegian adults with achondroplasia. Am J Med Genet A. 2019 Sep;179(9):1745-1755.