Clinical Images: Back pain, flattened vertebral bodies, and a novel mutation in the <scp><i>TRAPPC2</i></scp> gene

A 28-year-old man with a five-year history of progressive hip and back pain was admitted to our clinic. He reported bilateral hip joint pain exacerbated by squatting and standing up. Over time, he developed back pain without morning stiffness. Physical examination revealed a short neck, anterior lumbar convexity, and barrel chest and normal intelligence (Figure 1A). The patient tested positive for HLA-B27 and was diagnosed with ankylosing spondylitis at another hospital, whereas bone erosion was not observed in the computed tomography scan of the sacroiliac joints. There was no history of consanguineous marriage in his parents. Inflammatory ranges were within normal limits. The x-ray of the vertebrae demonstrated thoracolumbar scoliosis (Figure 1B), flattened vertebral bodies, and hump-like bony projections in the centroposterior portions of upper and lower endplates (Figure 1C red arrow). Pelvic magnetic resonance imaging and extremity joint x-rays did not show significant abnormalities. Whole-exome sequencing identified a homozygous frameshift mutation p.Q131Vfs*37 (c.391_392del) in the TRAPPC2 gene (Figure 1D), which is a novel mutation in Asian individuals. Given that the patient's parents were wild-type for the gene, the patient was identified as having a de novo mutation. Although his daughter was heterozygous for the mutation, it is theoretically nonpathogenic due to a recessive inheritance. The patient recalled growth and development obstacles starting at the age of six, gradually developing scoliosis and asymmetric lower extremities. A diagnosis of late-onset spondyloepiphyseal dysplasia tarda (SEDT) was made.1 The condition is often misdiagnosed as juvenile idiopathic arthritis due to its early onset and joint pain. Differential diagnosis includes other forms of dwarfism and degenerative joint diseases such as progressive pseudorheumatoid dysplasia,2 an inheritable disorder, which can be distinguished by the presence of joint swelling and hand involvement. Recognizing the clinical and radiographic features of SEDT is important for an accurate diagnosis. Gene sequencing provides valuable information for genetic counseling and family planning. Supported by the Shanghai Rising-Star Program (Yangfan Special Project; 22YF1432900).