A young boy with rash, arthritis, and developmental delay: Monogenic lupus due to DNASE2 gene defect.

Monogenic causes are increasingly being recognized in patients with lupus, especially in early-onset disease. We herein report a boy with a novel mutation in the DNase 2 (DNASE2) gene presenting with monogenic lupus. A 6-year-old boy with a global developmental delay with microcephaly presented with chronic febrile illness with anemia, rash, polyarthritis, renal involvement, and hepatosplenomegaly. Laboratory investigations revealed positive antinuclear antibody, high anti-dsDNA antibody titers, hypocomplementemia, hypergammaglobulinemia, nephrotic range proteinuria, and diffuse proliferative glomerulonephritis. Magnetic resonance imaging of brain showed altered signal intensity in subcortical white matter in bilateral fronto-parieto-temporal lobes. Targeted next-generation sequencing revealed a novel pathogenic variant in DNASE2. He was treated with oral prednisolone, mycophenolate mofetil, cyclosporine, and hydroxychloroquine and is doing well on follow up. DNASE2 deficiency has been reported as a rare genetic cause of monogenic lupus. DNASE2 deficiency should be suspected in patients with early-onset lupus with polyarthritis, erythematous rash, and neurological involvement.