In turn, immune function decreases and infection opportunities increase. One of the most common mutations deletes 28 DNA nucleotides from the C2 gene. Therefore, no C2 protein which can help make C3-convertase is produced. Ultimately, this delays/decreases immune response. C3: In terms of deficiency of C3, it has been found that 17 mutations in the C3 gene cause problems with C3. This rare condition mutates or prevents C3 protein from forming, lowering the immune systems ability to protect. C4: C4 deficiency is highly associated with systemic lupus erythematosus. Aβ42, a protein involved in Alzheimers disease, can cause activation of C4 (even in plasma deficient of C1q). At least one study indicates that the genetic variation of C4 plays a role in schizophrenia. Diagnosis
The diagnostic tests used to diagnose a complement deficiency include:
CH50 measurement
Immunochemical methods/test
C3 deficiency screening
Mannose-binding lectin (lab study)
Plasma levels/regulatory proteins (lab study)

Types
Disorders of the proteins that act to inhibit the complement system (such as C1-inhibitor) can lead to an overactive response, causing conditions such as hereditary angioedema. Disorders of the proteins that act to activate the complement system (such as C3) can lead to an underactive response, causing greater susceptibility to infections. Treatment
In terms of management for complement deficiency, immunosuppressive therapy should be used depending on the disease presented. A C1-INH concentrate can be used for angio-oedema (C1-INH deficiency).Pneumococcus and Haemophilus infections can be prevented via immunization. Epsilon-aminocaproic acid could be used to treat hereditary C1-INH deficiency, though the possible side effect of intravascular thrombosis should be weighed.
In February 2018, the funding was approved for people under 18 years old.In August 2018, the National Institute for Health and Care Excellence (NICE), which weighs the cost-effectiveness of therapies for the NHS in England and Wales, recommended against offering nusinersen to people with SMA. Children with SMA type 1 were treated in the UK under a Biogen-funded expanded access programme; after enrolling 80 children, the scheme closed to new people in November 2018. In May 2019, however, NICE reversed its stance and announced its decision to recommend nusinersen for use across a wide spectrum of SMA for a 5-year period.The Irish Health Service Executive decided in February 2019 that nusinersen was too expensive to fund, saying the cost would be about €600,000 per patient in the first year and around €380,000 a year thereafter "with an estimated budget impact in excess of €20 million over a five-year period" for the 25 children with SMA living in Ireland. Both the manufacturer and patient groups disputed the numbers and pointed out that actual pricing arrangements for Ireland are in line with the negotiated price for the BeneluxA initiative which Ireland has been a member of since June 2018.As of May 2019, nusinersen was available in public healthcare in more than 40 countries.In December 2021, nusinersen was included in the extended insurance coverage of China, and the price was reduced from ¥697,000 per vial to around ¥33,000 (~US$5,100) per vial. References
Further reading
External links
"Cut and Paste: Treating Spinal Muscular Atrophy with Nusinersen". Youreka Science. Retrieved 2019-05-28.