| Gene symbol | Gene location (chromosome) | OMIM ID for deficiency disorder | Inheritance pattern | Common pathogenic variant types | Founder effects and populations affected | Key references with PMIDs |
|---|---|---|---|---|---|---|
| **C5** | 9q33.2 | **C5 deficiency**; OMIM ID not confirmed from available contexts | Autosomal recessive | Missense, nonsense, frameshift/indel, compound heterozygous variants causing reduced/absent serum C5 and absent CH50/AH50; review reports **18 different mutations in >30 families** | No single classic founder effect established in the provided sources; cases reported in families of diverse origins; UK cohort found many affected individuals from consanguineous Asian families, though some antigenically low C5 cases were actually secondary to **CFH/CFI** defects rather than true C5 deficiency | Szymańska 2024 (review; 18 mutations in >30 families) (pqac-00000010); Hodeib 2020 lists C5 variants associated with IMD susceptibility (pqac-00000008); Shears 2022 cohort clarifies distinction from CFH/CFI-related secondary terminal pathway deficiency (pqac-00000004, pqac-00000007); Lizama-Muñoz 2025 family report with **p.Ile238Thr** and novel **p.Gly650Val** (pqac-00000012) |
| **C6** | 5p13 | **C6 deficiency**; **OMIM: 612446** | Autosomal recessive | Nonsense, loss-of-function, compound heterozygous variants; complete deficiency (C6Q0) vs subtotal deficiency (C6SD) | Strong founder effect reported historically in people of African ancestry; teaching source notes frequency about **1:1400 in African Americans**; first Chinese pedigree reported with compound heterozygous nonsense variants **p.Arg596Ter** and **p.Arg606Ter** | Li et al. 2020 (first Chinese pedigree; **OMIM 612446**) (pqac-00000011); Brodszki 2020 gene/chromosome/inheritance summary (pqac-00000015); Shears 2022 UK cohort includes C6-deficient patients (pqac-00000004, pqac-00000007); Sullivan teaching review on founder effect/frequency (pqac-00000002) |
| **C7** | 5p13 | **C7 deficiency**; OMIM ID not confirmed from available contexts | Autosomal recessive | Missense, nonsense, splice-region, regulatory/UTR variants, deletions; can include **functional hemizygosity** from 3'UTR instability plus coding variant; homozygous and compound heterozygous genotypes reported | Well-described founder effect in **Israeli Moroccan Jews**; teaching source notes frequency about **1:400**; Qatar case reports homozygous **p.Gly379Arg**, also observed in Moroccan-origin Israeli Jews | Balduit et al. 2023 systematic review and novel 3'UTR deletion with functional hemizygosity (pqac-00000006, pqac-00000009); Khalil et al. 2023 Qatar case with **c.1135G>C (p.Gly379Arg)** and founder note (pqac-00000003); Shears 2022 cohort includes C7 deficiency (pqac-00000004, pqac-00000007); Brodszki 2020 gene/chromosome/inheritance summary (pqac-00000015); Sullivan founder-effect summary (pqac-00000002) |
| **C8A / C8B / C8G** | **C8A/C8B:** 1p32; **C8G:** 9q34 | **C8 deficiency**; OMIM ID not confirmed from available contexts | Autosomal recessive | Pathogenic variants most often involve **C8B** (beta-chain deficiency) or **C8A/C8G** complex; missense and loss-of-function variants reported; functional deficiency may reflect absent/defective alpha-gamma or beta subunits | No single founder population established in the provided recent sources; UK cohort included multiple C8-deficient families; case literature also describes **C8B** variation such as **c.1625C>T (p.Thr542Ile)** in compound/heterozygous immune-imbalance context | Brodszki 2020 explicitly notes chromosome positions and AR inheritance for **C8α–γ/C8β** (pqac-00000015); Shears 2022 UK cohort includes C8 deficiency (pqac-00000004, pqac-00000007); Mannes et al. 2023 discusses **C8B p.Thr542Ile** and functional impairment context (from search results summarized in conversation) (pqac-00000015) |
| **C9** | 5p14–p12 | **C9 deficiency**; OMIM ID not confirmed from available contexts | Autosomal recessive | Loss-of-function variants, including complete and partial deficiency; some cases may retain residual hemolytic activity relative to other terminal component defects | Strong founder effect in **Japanese** and other East Asian populations; teaching source notes frequency about **1:1000 in Japanese**; classic high prevalence in Orientals referenced in C6 paper | Brodszki 2020 gene/chromosome/inheritance summary (pqac-00000015); Sullivan founder-effect summary (**1:1000 Japanese**) (pqac-00000002); Li et al. 2020 notes contrast with common C9 deficiency in Oriental populations (pqac-00000011) |


*Table: This table summarizes the principal causal genes underlying late/terminal complement component deficiency (C5-C9), including chromosomal location, inheritance, recurrent variant classes, and notable population founder effects. It is useful for genetics-focused disease curation and for prioritizing molecular testing in suspected terminal pathway deficiency.*