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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed October 2012

What is SADDAN?

SADDAN (severe achondroplasia with developmental delay and acanthosis nigricans) is a rare disorder of bone growth characterized by skeletal, brain, and skin abnormalities.

All people with this condition have extremely short stature with particularly short arms and legs. Other features include unusual bowing of the leg bones; a small chest with short ribs and curved collar bones; short, broad fingers; and folds of extra skin on the arms and legs. Structural abnormalities of the brain cause seizures, profound developmental delay, and intellectual disability. Several affected individuals also have had episodes in which their breathing slows or stops for short periods (apnea). Acanthosis nigricans, a progressive skin disorder characterized by thick, dark, velvety skin, is another characteristic feature of SADDAN that develops in infancy or early childhood.

How common is SADDAN?

This disorder is very rare; it has been described in only a small number of individuals worldwide.

What genes are related to SADDAN?

Mutations in the FGFR3 gene cause SADDAN. The FGFR3 gene provides instructions for making a protein that is involved in the development and maintenance of bone and brain tissue. A mutation in this gene may cause the FGFR3 protein to be overly active, which leads to the disturbances in bone growth that are characteristic of this disorder. Researchers have not determined how the mutation disrupts brain development or causes acanthosis nigricans.

Related Gene(s)

Changes in this gene are associated with SADDAN.

  • FGFR3

How do people inherit SADDAN?

SADDAN is considered an autosomal dominant disorder because one mutated copy of the FGFR3 gene in each cell is sufficient to cause the condition. The few described cases of SADDAN have been caused by new mutations in the FGFR3 gene and occurred in people with no history of the disorder in their family. No individuals with this disorder are known to have had children; therefore, the disorder has not been passed to the next generation.

Where can I find information about diagnosis or management of SADDAN?

These resources address the diagnosis or management of SADDAN and may include treatment providers.

  • Gene Review: Achondroplasia (
  • Genetic Testing Registry: Severe achondroplasia with developmental delay and acanthosis nigricans (
  • MedlinePlus Encyclopedia: Acanthosis Nigricans (

You might also find information on the diagnosis or management of SADDAN in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about SADDAN?

You may find the following resources about SADDAN helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for SADDAN?

  • achondroplasia, severe, with developmental delay and acanthosis nigricans
  • SADDAN dysplasia
  • Severe achondroplasia with developmental delay and acanthosis nigricans
  • Skeleton-skin-brain syndrome
  • SSB syndrome

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about SADDAN?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding SADDAN?

acanthosis nigricans ; apnea ; autosomal ; autosomal dominant ; cell ; developmental delay ; disability ; dysplasia ; gene ; mutation ; protein ; short stature ; stature ; syndrome ; tissue

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Bellus GA, Bamshad MJ, Przylepa KA, Dorst J, Lee RR, Hurko O, Jabs EW, Curry CJ, Wilcox WR, Lachman RS, Rimoin DL, Francomano CA. Severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN): phenotypic analysis of a new skeletal dysplasia caused by a Lys650Met mutation in fibroblast growth factor receptor 3. Am J Med Genet. 1999 Jul 2;85(1):53-65. (
  • Cohen MM Jr. Some chondrodysplasias with short limbs: molecular perspectives. Am J Med Genet. 2002 Oct 15;112(3):304-13. Review. (
  • Kumar KV, Shaikh A, Sharma R, Prusty P. SADDAN syndrome. J Pediatr Endocrinol Metab. 2011;24(9-10):851-2. (
  • Vajo Z, Francomano CA, Wilkin DJ. The molecular and genetic basis of fibroblast growth factor receptor 3 disorders: the achondroplasia family of skeletal dysplasias, Muenke craniosynostosis, and Crouzon syndrome with acanthosis nigricans. Endocr Rev. 2000 Feb;21(1):23-39. Review. (
  • Zankl A, Elakis G, Susman RD, Inglis G, Gardener G, Buckley MF, Roscioli T. Prenatal and postnatal presentation of severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN) due to the FGFR3 Lys650Met mutation. Am J Med Genet A. 2008 Jan 15;146A(2):212-8. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: October 2012
Published: February 8, 2016