Some patients with mutations of the FGFR3 gene will develop the SADDAN syndrome - severe achondroplasia, developmental delay and acanthosis nigricans.


Chromosome affected: 4p16.3


Gene affected: fibroblast growth factor receptor 3 (FGFR3)


Clinical features of SADDAN:

(1) achondroplasia

(2) developmental delay, mental retardation

(3) acanthosis nigricans


The differential diagnosis includes Muenke syndrome and Couzon syndrome with acanthosis nigricans. which also affects FGFR3.


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