Mevalonate kinase deficiency (MKD) is an autosomic recessive auto-inflammatory disease caused by mutations of the MVK gene. MKD being a very rare disease, numerous misdiagnoses and medical referrals may precede the right diagnosis, amplifying the burden of the disease.

To evaluate the patient's medical referrals between the first symptom and the diagnosis of MKD and the diagnosis delay.

A questionnaire was sent to French paediatric and adult rheumatologists to retrospectively collect information from genetically confirmed patients with MKD regarding the first symptoms of the disease, the different diagnoses made previously, the treatments received, and the disease burden evaluated mainly by the number of hospitalizations.

Thirteen patients were analyzed. The mean age at onset was 9.5months (birth to 36months). The average diagnosis delay was 7.1years. Eleven of them were hospitalized at least 5 times before the establishment of the diagnosis. A wide variety of diseases had been suspected: systemic juvenile idiopathic arthritis, periodic fever aphtous stomatitis pharyngitis adenitis syndrome, other hereditary recurrent fever, vasculitis, connective tissue disease, inflammatory bowel disease, gastritis, infections and immunodeficiency. Before the right diagnosis, 9 patients received corticosteroids and 6 patients received non-steroidal-anti-inflammatory drugs. Half patients had received repeated antibiotics, one third had received intravenous immunoglobulin, and the others were treated with immunosuppressive drugs or hydroxychloroquine.

MKD is a serious disease still difficult to treat, however earlier accurate medical referral and care, by increasing physicians’ awareness, is critical to improve both the disease course and quality of life.