Schimke versus non-Schimke chronic kidney disease: An anthropometric approach

Schimke-immuno-osseous dysplasia is a rare autosomal-recessive multisystem disorder with the main clinical features of disproportionate growth deficiency, defective cellular immunity, and progressive renal disease. It is caused by mutations of SMARCAL1, a gene encoding a putative chromatin remodeling protein of unknown function. Because a detailed description of the clinical features is an essential first step in elucidating the function of SMARCAL1, we present the first detailed anthropometric data for Schimke-immuno-osseous dysplasia patients. By comprehensive anthropometric examination (28 parameters) of 8 patients (3 females) with the typical findings of Schimke-immuno-osseous dysplasia (mean age: 14.8 years; range: 4.9-30.5 years) and 304 patients (117 females) with congenital and hereditary chronic kidney disease (mean age: 10.7 ± 4.8 years; range: 3-21.8 years), we show that Schimke-immuno-osseous dysplasia patients differ significantly from those with other forms of chronic kidney disease. z scores were calculated with reference limits derived from 5155 healthy children (2591 females) aged 3 to 18 years. The key finding was that, in the latter group, median leg length was significantly more reduced than sitting height, whereas in Schimke-immuno-osseous dysplasia patients, the reduction of sitting height was significantly more pronounced than for leg length. Therefore, the ratio of sitting height/leg length might be a simple tool for the clinician to distinguish Schimke-immuno-osseous dysplasia from other chronic kidney disease patients. Schimke-immuno-osseous dysplasia is very likely if this ratio is <0.83. However, other forms of chronic kidney disease have to be discussed in case of a ratio >1.01.