Features include always present findings: Discoid lupus rash, Malar rash, Elevated erythrocyte sedimentation rate, and Oral ulcer and others; and common findings: Recurrent lower respiratory tract infections, Antinuclear antibody positivity, Atelectasis, and Low red blood cell count (anemia) and others.

C1QB encodes complement C1q B chain (253 aa). Core component of the complement C1 complex, a multiprotein complex that initiates the classical pathway of the complement system, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system. Highest expression in Spleen (1,607 TPM) and Lung (443.3 TPM).

C1Q deficiency 2 is associated with mutations in the C1QB gene on chromosome 1.

The C1QB protein participates in C1QBP, C1QBP:KRT1, PLAUR:KRT1, p14ARF LOF mutants (C1QBP), and kallikrein:KNG1:C1QBP, C1QBP:KRT1, PLAUR:KRT1 pathways.

C1QB is classified as a druggable target (Cell Surface and Druggable Genome categories) with score 0.0.

Genetic testing for C1QB is available. Testing is considered confirmatory for diagnosis.

Biomarker and diagnostic research for C1Q deficiency 2 has been reported in the published literature.

Phenotype severity distribution: 11 always present features, 13 common features.

No clinical trials have been registered for C1Q deficiency 2.

22 publications have been identified in PubMed for C1Q deficiency 2. Research spans Basic Science / Preclinical (64%), Case Report / Case Series (18%), and Review / Meta-Analysis (9%).