Impairment of Body Growth in Mucopolysaccharidoses

Abstract

Children with mucopolysaccharidoses (MPS) grow poorly and become physically handicapped because of systemic bone disease. For children with skeletal dysplasias, such as MPS, it is important to know the natural history of growth. Understanding of the growth pattern provides assessment of current growth and data on efficacy of individualized medicine in growth-promoting treatments. The purpose of this chapter is to review natural history of growth patterns for MPS II, IVA, and VI patients. The cross-sectional and/or longitudinal data were collected to develop growth curves for the following types of MPS. Interestingly, accelerated growth has been observed in the first years of life in any type of MPS reviewed here, followed by slowing growth rate and growth failure. (1) MPS II: We obtained height and weight measurements from 46 Japanese male patients with MPS II. Mean birth length of boys was 50.9 ± 2.1 cm. The mean height for MPS II at 18 years of age or older was 127.2 ± 8.5 cm. These values corresponded to 0.9 SD and −7.5 SD of the height for normal Japanese males. The mean height was kept higher until 5 years and the mean weight was heavier until 8 years of age. After 7 years of age, short stature was commonly observed in spite of clinical severity by CNS involvement. (2) MPS IVA: Height and weight measurements from 193 girls and 195 boys with MPS IVA were collected. Mean birth lengths of boys and girls were 52.4 ± 3.9 and 52.1 ± 2.9 cm, respectively. Mean heights for males and females at 18 years of age were 119.3 ± 22.6 and 113.5 ± 23.1 cm, respectively. These values correspond to −8.0 SD and −7.7 SD of the mean height for normal males and females. Mean birth weights for boys and girls were 3.56 ± 0.5 and 3.5 ± 0.7 kg, respectively. (3) MPS VI: Growth is severely impacted on this type of MPS. In an observational study in 121 untreated MPS VI patients, a mean height was 115.2 cm ± 26.1 cm and median height was 103.7 cm with a range of 80–169 cm. An inverted correlation of height with the excretion of urinary GAGs and an influence of the genotype on the pattern of this excretion were also demonstrated. Thus, the growth pattern in MPS II patients was characterized by impaired growth velocity after 4 years of age, while the growth patterns in MPS IVA and VI patients were characterized by impaired growth velocity after 1 and 2 years of age.