Monogenic lupus with neuroregression in an infant due to rare compound heterozygous variants in C1QA gene: Case-based review.

Monogenic lupus is a rare variant of systemic lupus erythematosus (SLE) that develops in patients with a single gene disorder. Early complement component deficiencies were the first forms of monogenic lupus to be described, and C1Q gene mutations are one of the most common forms. C1QA complement deficiency has been reported to occur usually due to biallelic variants in C1QA gene, and compound heterozygous variants in C1QA gene have rarely been reported. A majority of monogenic lupus patients with C1Q deficiency present with mucocutaneous, renal, and musculoskeletal manifestations. Our patient is an unusual case of monogenic lupus with severe neurological manifestations along with cutaneous, haematological, and hepatic manifestations secondary to rare compound heterozygous variants in C1QA gene and antiribosomal P autoantibody positivity. She was treated with glucocorticoids, rituximab, and fresh frozen plasma with partial neurological recovery. Thus, we present a unique case of monogenic lupus due to a rare compound heterozygous variant in C1QA gene with a brief review of literature.