Wiedemann-Steiner syndrome is a rare genetic disorder that causes developmental delay, unusual facial features (dysmorphism), short stature, and reduction in muscle tone. It is inherited in an autosomal dominant fashion, but all cases reported so far were sporadic. The syndrome was originally described in 1989.
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Cause
Wiedemann-Steiner syndrome results from mutations in the MLL (also known as KMT2A) gene on the long arm of chromosome 11. The gene encodes a histone-modification enzyme — that is, it helps modify the expression of other genes. The condition is autosomal dominant, meaning that only one abnormal copy of the gene is needed for a person to have the syndrome. In all but one reported case, the mutation occurred de novo — that is, neither parent was affected. In the single exception, both a father and his son were diagnosed.
The mechanism by which mutations in the MLL gene cause the phenotype of Wiedemann-Steiner syndrome is not yet known.
Features
Features described in Wiedemann-Steiner syndrome include:
Diagnosis
If Wiedemann-Steiner syndrome is suspected, analysis of the MLL gene can be carried out. Otherwise, it may be diagnosed by whole-exome sequencing.
Treatment
There is no specific cure or treatment for Wiedemann-Steiner syndrome. Children with this condition may benefit from a range of supportive treatments such as physiotherapy, speech therapy, supplementary nutrition for poor feeding, and special educational support.