Identification of co-occurrence in a patient with Dent's disease and ADA2-deficiency by exome sequencing.

Patients with co-occurrence of two independent pathologies pose a challenge for clinicians as the phenotype often presents as an unclear syndrome. In these cases, exome sequencing serves as a powerful instrument to determine the underlying genetic causes. Here, we present the case of a 4-year old boy with proteinuria, microhematuria, hypercalciuria, nephrocalcinosis, livedo-like rash, recurrent abdominal pain, anemia and continuously elevated CRP. Single exome sequencing revealed the pathogenic nonsense mutation p.(Arg98*) in the CLCN5 gene causing the X-linked inherited, renal tubular disorder Dent's disease. Furthermore, the two pathogenic and compound heterozygous missense variants p.(Gly47Ala) and p.(Pro251Leu) in the CECR1 gene could be identified. Mutations in the CECR1 gene are associated with a hereditary form of polyarteritis nodosa, called ADA2-deficiency. Both parents were carriers of a single heterozygous variant in CECR1 and the mother was carrier of the CLCN5 variant. This case evidently demonstrates the advantage of whole exome sequencing compared to single gene testing as the pathology in the CECR1 gene might have only been diagnosed after the occurrence of signs of systemic vasculitis like strokes or hemorrhages. Therefore, treatment and prevention can now start early to improve the outcome of these patients.