The Medical Burden Of Rare Autoinflammatory Diseases: Exemple Of Mevalonate Kinase Deficiency In France

Background Mevalonate kinase deficiency (MKD) is a very rare autosomic recessive autoinflammatory disease caused by mutations of the MVK gene. Two phenotypes of MKD are delineated according to the level of enzymatic deficiency, complete (MA) or partial (HIDS), however a wide spectrum of intermediate phenotypes has been reported. First symptoms of MKD appear very early in life, occasionally with severe neonatal hepatitis, but most patients will undergo an extensive workup before coming to the diagnosis sometimes many years later. The fact that MKD deficiency is rare means that a quantity of mistaken diagnoses and medical referrals will precede the right diagnosis, amplifying the burden of the disease. Objectives A retrospective survey and chart review to evaluate the patient9s medical referrals between the first symptom and the diagnosis of MKD. Methods A questionnaire was sent to French paediatric and adult rheumatologists to collect information from genetically confirmed MKD patients, regarding the first symptoms of the disease, the different diagnoses previously made with the treatment received, and the disease burden evaluated by the hospitalizations. Results Thirteen patients were analyzed (11 HIDS and 2 MA). The median age at onset was 9.5 months (from birth to 36 months) in twelve cases. The average diagnosis delay was 7.1 years. A wide variety of diseases had been suspected: systemic JIA, PFAPA syndrome, other hereditary recurrent fever (FMF, TRAPS, CINCA), vasculitis (Kawasaki, Henoch Scholein purpura), connective tissue disease, lupus, digestive inflammatory bowel disease, gastritis, infections (recurrent viral infection, recurrent UTI, maternal to foetal infection), and immunodeficiency. Before the right diagnosis, 9 patients received corticosteroids and 6 patients received NSAIDS. Half patients had received repeated antibiotics, one third had received IV Immunoglobulin, and others were treated with immunosuppressive drugs (ciclosporine and methotrexate), and hydroxychloroquine. Eleven on 13 patients were hospitalized at least 5 times before the establishment of the diagnosis. Conclusions MKD is a serious disease still difficult to treat, however earlier accurate medical referral and care, by increasing physicians9 awareness, is critical to improve both the disease course and the quality of life. Disclosure of Interest : None declared DOI 10.1136/annrheumdis-2014-eular.5636