CISS is a genetically heterogeneous disorder caused by mutations in CRLF1 in more than 90 percent of patients (CISS1) and by mutations in CLCF1 in the remaining patients (CISS2). It is now well demonstrated that all patients with an infantile-onset CS will develop CISS, confirming that CS and CISS are not “allelic disorders” but the same clinical entity described at different ages of affected patients.
Here we report on a Turkish patient with a phenotype consistent with CS/CISS1 and a nonsense homozygous mutation (c.829C>T, p.R277X) in the CRLF1 gene. This mutation has already been reported in another Turkish patient with CS/CISS1.