Growth hormone receptor deficiency (Laron syndrome) in black African siblings.

Non-Caucasians with growth hormone receptor (GHR) deficiency/Laron syndrome among the approximately 180 recognised cases are rare, and include a Japanese and 3 African Americans. Black African siblings, a brother and a sister seen initially at 11 years 9 months and 5 years 6 months of age respectively were -7,4 and -8,0 on the standard deviation score for height. They had characteristic features and biochemical findings including prominent forehead; depressed nasal bridge; central adiposity; high-pitched voices; micropenis; high GH levels and low levels of insulin-like growth factor (IGF)-I, IGF-II, insulin-like growth factor-binding protein 3 (IGFBP-3), and GH-binding protein (the solubilised extracellular domain of the GH cell surface receptor). Molecular genetic studies revealed a dinucleotide deletion in both siblings on exon 7 of the GHR gene, a mutation not found in any other GHR-deficient patient studied, including the North Americans of African origin. Since African Americans have a substantial admixture of Caucasian genes, it is of interest to document the presence of this condition in siblings from Africa.