Lou et al. proposed that infantile-onset, early lethal SIOD would result from presence of at least one SMARCAL1 null allele (deletion, nonsense, or frameshift mutation), whereas a juvenile form with less severe phenotype and survival into the second and third decade of life would arise from missense mutations [13,15]. The gene discussed is SMARCAL1; the disease is Schimke immuno-osseous dysplasia.