Case report of Camptodactyly-Arthropathy-Coxa vara-Pericarditis syndrome in combination with autoimmune disease

Camptodactyly-Arthropathy-Coxa vara-Pericarditis (CACP) syndrome is a rare genetic disorder (prevalence <1/1 000 000) characterized by early-onset camptodactyly, noninflammatory arthropathy with synovial hyperplasia and occasionally progressive coxa vara deformity or noninflammatory pericarditis. It is caused by a mutation in the proteoglycan 4 (PRG 4) gene which encodes lubricin that is the main lubricant in synovial fluid and cartilage surface. Simultaneous autoimmune disease has never been described. Case report: A 7-year old boy was admitted to Children's Clinical University Hospital in January 2016 with a history of Juvenile idiopathic arthritis (JIA), rheumatoid factor positive lasting for three years. The patient has been under the doctor’s observation since the neonatal period, he was born prematurely, had a delay of psychomotor and language development, gait disturbances, and generalized muscle weakness. Deformities of knee and wrist joints without pain or morning stiffness were observed at the age of 4-year. As the diagnosis of JIA was made, he received appropriate therapy with NSAID, methotrexate, intra-articular glucocorticoid injections. Despite the therapy clinical condition aggravated, he had contractures of joints, hepatosplenomegaly, cardiomegaly, autoimmune thyroiditis, miopathy approved histologically and in EMG. Overlap syndrome was suspected with high ANA, ENA, anti-Ro, anti-La, Sm, RNP antibodies. In collaboration with Hamburg Centre for Pediatric and Adolescent Rheumatology biological therapy was initiated – initially with TNF inhibitor Etanercept which was ineffective, therefore was changed to Il-6 receptor inhibitor Tocilizumab. After repeated metabolic and genetic investigations in October 2018 diagnosis of CACP was confirmed. Although biological therapy is not effective in CACP syndrome, we observed significant clinical improvement after initiation of Tocilizumab, therefore this therapy is still ongoing. The CACP syndrome is very rare and commonly misdiagnosed as JIA. The efficacy of Tocilizumab may indicate that in our case there is an ongoing autoimmune process alongside.