A novel mutation in the proteoglycan 4 gene causing CACP syndrome: two sisters report

Abstract

Background: Camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome, caused by biallelic pathogenic mutations in the proteoglycan 4 (PRG4) gene, is characterized by early-onset camptodactyly, noninflammatory arthropathy, coxa vara deformity, and rarely, pericardial effusion. This syndrome can mimic juvenile idiopathic arthritis. CACP syndrome is caused by mutations in the proteoglycan 4 (PRG4) gene. To date, only 36 pathogenic mutations have been reported in this gene, but none have been reported from Azerbaijan.

Case presentation: Herein, we report two siblings presented with chronic polyarthritis, had a prior diagnosis of juvenile idiopathic arthritis, but was subsequently diagnosed as CACP syndrome with novel mutation in the PRG4 gene.

Conclusion: Our report expands the knowledge of PRG4 mutations, which will aid in CACP patient counseling.

Keywords: Arthropathy; Camptodactyly; Coxa vara; PRG4 mutation.

Fig. 1

Radiological evaluation of “Patient 1”. a Depicts narrowing of the wrist joint spaces with periarticular loss of bone dansity. Contractures were observed in the distal interphalangeal joints. Subchondral cysts were observed in the distal epiphysis of both radius and ulna. The 5th metacarpal bone of the left hand was short. b Bilateral hip joint spaces are markedly narrowed. Bilateral coxa vara deformity was observed. Bilateral femoral heads were flat, femoral necks were short. c The joint space was narrowed in both knees. d Chronic degenerative changes were observed in both hip joints. Coxa vara deformity, narrowing of the joint spaces, millimetric subchondral cysts on the femoral heads were observed. The changes were more prominent on the left side. Coxa magna deformity was detected in the left femur. e Fluid increase in the joint space and contrast enhancement consistent with synovitis were observed on the left side

Fig. 2

Radiological evaluation of “Patient 2”. a Skeletal survey reveals heterogeous lucensies of the carpal bones, distal radial and ulnar epiphysis. The joint spaces in the wrists and proximal and distal interphalangeal joints were markedly narrow. Periarticular bone resorption in MCP, PIP, DIP joints and carpal bones were noted. b Both hip joint spaces were narrow and coxa vara deformity was present. c Periarticular bone resorption adjacent to knee joints were observed along with joint space narrowing. Lucensies were noted on the proximal diaphysis of left tibia. d Millimetric subchondral cysts on the humeral head and dense fluid in the joint space and subscapular bursa. e The synovium enhanced after contrast administration consistent with synovitis