X-linked Acrogigantism is characterised by gigantism that has an onset in early childhood (<5 years of age) and is caused by an excess of growth hormone.  Affected individuals grow rapidly during infancy.  At time of diagnosis they show marked overall somatic growth, with elevated weight and an enlarged head circumference.

Duplications of the GPR101 gene (Xq26.3) have been shown to cause X-linked Acrogigantism (Trivellin et al 2014 N Engl J Med. 371:2363-74) and account for more than 80% of the cases of early-onset paediatric gigantism (Lodish et al 2016 Curr Opin Endocrinol Diabetes Obes 23:72-80)

Uncertainty of measurement for the GPR101 ddPCR assay is available upon application to the laboratory.