© Martinez-Agosto Laboratory, Department of Human Genetics, University of California, Los Angeles, 2008-2015.

 

Hemihyperplasia

Description:
Isolated hemihyperplasia is an abnormality of cell proliferation leading to asymmetric overgrowth of one or more regions of the body. The term 'hemihyperplasia' has replaced the term 'hemihypertrophy' to describe accurately the increase in cell number found in these patients. The incidence of isolated hemihyperplasia is estimated to be 1 in 86,000. Idiopathic hemihypertrophy is associated with increased risk of embryonal cancers in childhood, particularly Wilms tumor.

Hoyme et al. (1998) provided an anatomic classification of hemihyperplasia: complex hemihyperplasia is involvement of half of the body, including at least 1 arm and 1 leg; affected parts may be contralateral or ipsilateral. Simple hemihyperplasia is involvement of a single limb. See also facial hemihyperplasia.

Although isolated hemihyperplasia is a distinct clinical entity, it can also occur as a feature of overgrowth syndromes, including Beckwith-Wiedemann syndrome, neurofibromatosis, Proteus syndrome, and Klippel-Trenaunay-Weber syndrome.

Testing:
Isolated hemihypertrophy is, in fact, part of the spectrum of phenotypes of Beckwith-Wiedemann syndrome: methylation studies of the LIT1 and H19, and mosaic paternal uniparental disomy for 11p15.

Idiopathic hemihypertrophy is associated with increased risk of embryonal cancers in childhood.

More information:
Hemihyperplasia