Context and objective
GH insensitivity with immune dysfunction caused by STAT5B mutations is an autosomal recessive condition. Heterozygous mutations in other genes involved in growth regulation were previously associated with a mild height reduction. Our objective was to assess for the first time the phenotype of heterozygous STAT5B mutations.
Methods
We genotyped and performed clinical and laboratory evaluations in 52 relatives of two previously described Brazilian brothers with homozygous STAT5B c.424_427del mutation (21 heterozygous). Additionally, we obtained height data and genotype from 1104 adult control individuals from the same region in Brazil and identified five additional families harboring the same mutation (18 individuals, 11 heterozygous). Furthermore, we gathered the available height data from first-degree relatives of patients with homozygous STAT5B mutations (17 individuals from seven families). Data from heterozygous individuals and non-carriers were compared.
Results
Individuals carrying heterozygous STAT5B c.424_427del mutation were 0.6 SDS shorter than their non-carrier relatives (P=0.009). Heterozygous subjects also had significantly lower SDS for serum concentrations of IGF1 (P=0.028) and IGFBP3 (P=0.02) than their non-carrier relatives. The 17 heterozygous first-degree relatives of patients carrying homozygous STAT5B mutations had an average height SDS of −1.4±0.8 when compared with population-matched controls (P< 0.001).
Conclusions
STAT5B mutations in the heterozygous state have a significant negative impact on height (∼3.9 cm). This effect is milder than the effect seen in the homozygous state, with height usually within the normal range. Our results support the hypothesis that heterozygosity of rare pathogenic variants contributes to normal height heritability.