Phenotypic heterogeneity of ZMPSTE24 deficiency

A 4-year-old girl was referred to the Undiagnosed Diseases Network with a history of short stature, thin and translucent skin, macrocephaly, small hands, and camptodactyly. She had been diagnosed with possible Hallerman-Streiff syndrome. Her evaluation showed that she was mosaic for uniparental isodisomy of chromosome 1, which harbored a pathogenic c.1077dupT variant in ZMPSTE24 which predicts p.(Leu362fsX18). ZMPSTE24 is a zinc metalloproteinase that is involved in processing farnesylated proteins and pathogenic ZMPSTE24 variants cause accumulation of abnormal farnesylated forms of prelamin A. This, in turn, causes a spectrum of disease severity which is based on enzyme activity. The current patient has an intermediate form, which is a genocopy of severe Progeria.