Features include: Systemic lupus erythematosus, Hashimoto thyroiditis, Liver inflammation (hepatitis), and Abnormality of complement system.

C1S encodes complement C1s (688 aa). 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 Ovary (882.0 TPM) and Fallopian Tube (622.2 TPM).

Complement component C1s deficiency is associated with mutations in the C1S gene on chromosome 12.

The C1S protein participates in C1S N-terminal fragment, C1S C-terminal fragment, and Activation of C1s pathways.

C1S is classified as a druggable target (Druggable Genome, Enzyme, and Protease categories) with score 10.4.

Genetic testing for C1S is available. Testing is considered confirmatory for diagnosis.

No clinical trials have been registered for complement component C1s deficiency.

2 publications have been identified in PubMed for complement component C1s deficiency. Research spans Review / Meta-Analysis (50%) and Epidemiology / Natural History (50%).

Recent Publications

• Subia NT (2025). [PMID: 40971888](https://pubmed.ncbi.nlm.nih.gov/40971888/). *Journal of immunology (Baltimore, Md. : 1950)*. [Epidemiology / Natural History]

• McMurray JC (2024). [PMID: 39294906](https://pubmed.ncbi.nlm.nih.gov/39294906/). *Allergy and asthma proceedings*. [Review / Meta-Analysis]