A case of spondyloepiphyseal dysplasia tarda caused by a novel intragenic deletion of TRAPPC2

Spondyloepiphyseal dysplasia tarda (SEDT; MIM # 313400) is a rare X-linked recessive skeletal disease characterized by disproportionate short stature with vertebral malformation and degenerative changes involving the spine and major joints (1). During infancy and early childhood, affected males show normal development and unremarkable findings on radiographs (1). Clinical expression of SEDT begins with a flattening of the growth curve before puberty. At this time, radiographs show characteristic deformities of the vertebrae, including platyspondyly with a posterior hump. Degenerative joint disease is a common problem in male patients making hip joint replacement often necessary in the fourth or fifth decade of life (2). The causative gene of SEDT is TRAPPC2, which encodes trafficking protein particle complex subunit 2, a 140 amino acid protein, also known as Sedlin. TRAPPC2 may play a role in vesicular transport from the endoplasmic reticulum to the Golgi (3, 4). To date, 50 TRAPPC2 mutations have been reported in families with SEDT of different ethnic origin (Human Gene Mutation Database; http://www.hgmd.cf.ac.uk/ac). The underlying mutations are spread over the entire coding region of the TRAPPC2 gene comprising exons 3-6, without clear genotype-phenotype correlation. Here, we report a Japanese SEDT patient with a novel intragenic deletion mutation in TRAPPC2.