Duplication of PTHLH causes osteochondroplasia with a combined brachydactyly type E/A1 phenotype with disturbed bone maturation and rhizomelia

Abstract

Parathyroid hormone-like hormone (PTHLH, MIM 168470) plays an important role in endochondral bone development and prevents chondrocytes from differentiating. Disease-causing variants and haploinsufficiency of PTHLH are known to cause brachydactyly type E and short stature. So far, three large duplications encompassing several genes including PTHLH associating with enchondromatas and acro-osteolysis have been described in the literature. Here, we report on a three-generation pedigree with short humerus, curved radius, and a specific type of severe brachydactyly with features of types E and A1 but without the enchondromatas and the acro-osteolysis. Microarray-based comparative genomic hybridization (array-CGH) revealed a 70-kb duplication on chromosome 12p11.22 encompassing only PTHLH. Our data extend the phenotypic spectrum associated with copy number variations of PTHLH, and this family is to our knowledge the first description harboring a microduplication encompassing only PTHLH.