The diagnosis of SIOD is made on clinical findings. The most definitive diagnostic findings are skeletal dysplasia (spondyloepiphyseal dysplasia), renal dysfunction (urinary protein loss), T lymphocyte deficiency (particularly for naïve CD4 and CD8 T cells), dysmorphic facial features, and hyperpigmented macules. Anthropometry can help to distinguish SIOD from other forms of chronic kidney disease: a sitting height: leg length ratio of < 0.83 is consistent with a diagnosis of SIOD whereas a ratio of > 1.01 is indicative of non-SIOD chronic kidney disease. DNA testing for mutations in the SMARCAL1 gene is available to confirm the diagnosis.

-National Organization for Rare Disorders