Sanfilippo Children Longer at Birth and Show Altered Growth: Study

New analysis sheds light on factors affecting growth patterns

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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Children with Sanfilippo syndrome have altered growth patterns — starting at birth, when infants with the genetic disorder are usually longer than the average newborn in the general population, a new study found.

But while the results showed overall variations in the growth dynamics for Sanfilippo children, researchers said these patterns generally are closer to normative trends than what is seen in related disorders.

The study, “Comparison of growth dynamics in different types of MPS: an attempt to explain the causes,” was published in the Orphanet Journal of Rare Diseases.

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Sanfilippo Growth Impairments Milder Than Other MPS Types

Sanfilippo syndrome is caused by genetic mutations that lead to a toxic accumulation of  heparan sulfate, a type of sugar molecule called a glycosaminoglycan or GAG. The disorder is part of a broader class of diseases called mucopolysaccharidosis (MPS), which are characterized by the toxic accumulation of GAGs.

MPS type III is another name for Sanfilippo syndrome.

Growth patterns in Sanfilippo

According to the researchers, the “growth pattern in patients with all types of mucopolysaccharidoses significantly deviates from the general population,” though these differences typically are less pronounced in Sanfilippo.

Now, the scientists delved into “over 30 years of observations of the growth dynamics in patients with different types of MPS,” reporting on growth outcomes for 195 children cared for at the Children’s Memorial Health Institute, in Warsaw, Poland, from 1989 to 2020.

Among the children, 72 had Sanfilippo: 33 girls and 39 boys.

“There is a scarcity of literature concerning the process of growth in children with different types of MPS diseases,” the researchers wrote, adding, “Better understanding of the natural history of the disease can be achieved with long-term observations, which help detect and establish patterns of growth and physical development in the evaluated group.”

Compared with normative values in the general population, average body length at birth was significantly longer for children with Sanfilippo. Specifically, the lengths for girls were 53.4 cm versus 51.3 cm (21.0 in vs. 20.2 in), and for boys, 55.3 cm versus 52.2 cm (21.8 in vs. 20.6 in). All other forms of MPS also showed significant differences in birth length.

Girls with Sanfilippo also had significantly lower birth body weight — 3.15 kg vs. 3.4 kg, or 6.9 lbs vs. 7.5 lbs — though for boys with Sanfilippo, these measures did not differ significantly from normative values.

The measurement in head circumference also did not significantly differ for boys. For girls, this measurement was smaller: 33.7 cm vs. 34.5 cm (13.3 in vs. 13.6 in).

Analyses of growth dynamics during the early years of life showed that children with Sanfilippo, and also those with MPS types I and II, tended to experience marked growth in the first few years — up to about age 6, for Sanfilippo — followed by a substantial slowing in growth rates as the disease begins to progress.

Notably, of all the MPS types, children with Sanfilippo generally had growth dynamics over time that were most similar to what is considered typical. The researchers said that differences in growth dynamics between the types are likely attributable to differences in the specific GAGs that accumulate in each type.

“Patients with MPS III had the mildest growth impairments compared to other MPS patients,” the researchers concluded.