A Diagnostic Odyssey: Mevalonate Kinase Deficiency Revealed by Genetic Testing in Adulthood.

Mevalonate kinase deficiency (MKD) is a rare autosomal recessive autoinflammatory disorder with marked clinical heterogeneity, frequently leading to delayed diagnosis. We describe a 71-year-old woman with lifelong episodic inflammatory symptoms beginning in infancy, including recurrent fevers, lymphadenopathy, and gastrointestinal and mucocutaneous manifestations, later evolving into intermittent arthralgia, myalgia, and fatigue. A unifying diagnosis was established when genetic testing identified two missense pathogenic MVK variants consistent with compound heterozygous MKD, supported by elevated serum IgD levels and a characteristic clinical phenotype. This case illustrates the essential role of molecular genetic testing in resolving prolonged diagnostic odyssey, in guiding surveillance for complications such as AA amyloidosis, and enabling targeted therapeutic strategies.