| Domain | PEX19-specific evidence | Zellweger-spectrum extrapolation | Key sources |
|---|---|---|---|
| Identity | Peroxisome biogenesis disorder 12A (PBD12A; Zellweger phenotype), **OMIM 614886**, **MONDO:0013951**, caused by biallelic **PEX19** variants; historically complementation group **J**. It is distinct from **PEX3-associated PBD10A**. | Part of the autosomal-recessive Zellweger spectrum of peroxisome-biogenesis disorders. | Open Targets disease–gene evidence (pqac-00000000); Matsuzono et al., 1999, DOI: [10.1073/pnas.96.5.2116](https://doi.org/10.1073/pnas.96.5.2116), PMID: **10051604** (pqac-00000036, pqac-00000039) |
| Known human variants and cases | **c.763_764insA** (historically A764 insertion; C-terminal frameshift): homozygous in two brothers who died at 3 and 21 days. **c.320delA, p.Lys107SerfsTer13**: homozygous in one girl who died at 16 months. **p.Leu94Ter** (reported genomic coordinate chr1:g.160283009A>T): homozygous in a male neonate; a similarly affected sibling was not molecularly confirmed. Thus, the primary literature describes **four genetically confirmed children plus one highly suggestive sibling**. | No reliable population variant spectrum, recurrent founder allele, or genotype-specific frequency has been established because the reported cohort is extremely small. | Mohamed et al., 2010, DOI: [10.1002/ajmg.a.33560](https://doi.org/10.1002/ajmg.a.33560) (pqac-00000041, pqac-00000042); Adiyapatham & Murugesan, accepted **9 March 2023**, DOI: [10.1136/bcr-2022-252014](https://doi.org/10.1136/bcr-2022-252014) (pqac-00000005, pqac-00000006) |
| Inheritance and risk | Autosomal recessive. Reported variants were homozygous; consanguinity was present in the 2010 and 2023 families, and both parents of the c.320delA patient were carriers. | For two carrier parents, Mendelian recurrence risk is **25% affected, 50% carrier, and 25% unaffected/non-carrier per pregnancy**. Penetrance of biallelic null alleles appears high, but cannot be quantified. No anticipation, sex bias, protective allele, or established modifier is known. | Human segregation and family evidence (pqac-00000005, pqac-00000042) |
| Core phenotype | Antenatal or neonatal multisystem disease: profound hypotonia, weak cry/poor feeding and reflexes, seizures, craniofacial dysmorphism and large fontanelles/metopic suture; hydrocephalus, cerebral white-matter abnormalities, ventriculomegaly/colpocephaly or cerebellar-vermis hypoplasia; congenital heart defects; genital anomalies; corneal opacity; skeletal abnormalities or talipes. The longer-surviving child developed liver disease, global developmental delay, recurrent infection, renal tubular dysfunction and gallstones. | Other ZSD manifestations—sensorineural hearing loss, retinal degeneration, adrenal insufficiency, leukodystrophy, osteopenia/fractures and nephrolithiasis—are clinically relevant surveillance targets but have not all been demonstrated in PEX19 cases. | PEX19 cases (pqac-00000006, pqac-00000042, pqac-00000043); broader ZSD review (pqac-00000022, pqac-00000025) |
| Diagnostic biomarkers | In the c.320delA patient: elevated plasma **C26:0**, C26:0/C22:0 and C24:0/C22:0 ratios; deficient fibroblast C26:0 and pristanate β-oxidation, phytanate α-oxidation, DHAPAT activity and plasmalogens; abnormal acyl-CoA oxidase/thiolase processing; and absent peroxisomes by immunofluorescence. Routine ammonia, lactate and organic acids were normal in the 2023 neonate, illustrating that normal routine metabolic tests do not exclude PBD12A. | Recommended ZSD testing includes plasma VLCFAs, phytanic/pristanic and pipecolic acids, C27 bile-acid intermediates and erythrocyte plasmalogens, followed by fibroblast functional studies and molecular confirmation. | Mohamed et al. (pqac-00000042, pqac-00000043); 2023 case (pqac-00000021); aggregate diagnostic evidence (pqac-00000009, pqac-00000024) |
| Molecular mechanism | PEX19 is a predominantly cytosolic chaperone/import receptor that binds membrane-peroxisomal targeting signals, stabilizes newly synthesized peroxisomal membrane proteins and delivers them to PEX3/PEX16 for membrane insertion. Loss causes PMP degradation or mitochondrial mistargeting, failed peroxisomal membrane assembly and loss of matrix-protein import. Wild-type PEX19 restored peroxisomes in CG-J fibroblasts and CHO mutants. PEX19-deficient human cells also show defective ether-lipid-dependent GPI-anchor remodeling. | Downstream accumulation of VLCFAs, branched fatty acids and toxic bile-acid intermediates, together with reduced plasmalogens/DHA and altered redox homeostasis, is the accepted ZSD mechanism linking peroxisome failure to brain, liver, kidney, eye and skeletal injury. Exact causal contributions to each PEX19 phenotype remain incompletely resolved. | Human/cellular studies: DOI [10.1083/jcb.200304111](https://doi.org/10.1083/jcb.200304111) (pqac-00000014, pqac-00000019); CG-J rescue (pqac-00000037, pqac-00000039); GPI remodeling, DOI [10.1194/jlr.M021204](https://doi.org/10.1194/jlr.M021204) (pqac-00000051) |
| Prognosis | All four molecularly confirmed children died early: **3 days, 21 days, approximately 15 days, and 16 months**. Respiratory failure, severe infection/sepsis, coagulopathy and liver failure contributed. No PEX19-specific survival curve or 5-/10-year survival estimate exists. | Severe Zellweger syndrome generally causes death during infancy; survival into later childhood or adulthood pertains mainly to hypomorphic PEX variants and milder ZSD, not yet established for PEX19. | Human cases (pqac-00000041, pqac-00000042, pqac-00000021); broader ZSD prognosis (pqac-00000025) |
| Treatment and current applications | No curative or PEX19-targeted treatment is established. Reported care was supportive: ventilation/respiratory support, antiseizure treatment, nutrition, infection management, comfort/palliative care and genetic counseling. No PEX19-specific gene, RNA or cell therapy trial was identified. | ZSD-wide interventions remain supportive or investigational. Betaine was studied only in selected **PEX1** genotypes; hydroxychloroquine only in **PEX1/PEX6/PEX26** disease. Bile-acid therapy may improve hepatobiliary biomarkers or histology without proven alteration of overall course. Recruiting studies include the PBD natural-history cohort **NCT01668186** and retinopathy study **NCT06190626**; neither reports PEX19-specific outcomes. | Clinical records and review evidence (pqac-00000030, pqac-00000031, pqac-00000033, pqac-00000034) |
| Epidemiology | PEX19-specific prevalence, incidence, carrier frequency, sex ratio and geographic distribution are unknown. In a 613-cell-line ZSD series, only **4/613 (0.65%)** were assigned to PEX19, versus 3/613 to PEX3; the cohort was over 90% Western European and is not population based. | Overall ZSD birth incidence is commonly estimated near **1:50,000**, with reported geographic variation as low as approximately 1:500,000 in Japan; these figures must not be presented as PBD12A incidence. | Aggregate fibroblast cohort (pqac-00000008, pqac-00000010); ZSD estimates (pqac-00000021, pqac-00000025) |
| Evidence limitations | Evidence rests on three case publications, patient fibroblasts and experimental models. Phenotype percentages calculated from four confirmed patients would be unstable and ascertainment-biased. Allele frequencies and modern ACMG/AMP classifications were not consistently reported; the 2023 paper’s 0.002% figure came from an internal database rather than a specified population database. | Most diagnostic, surveillance and treatment recommendations necessarily derive from ZSD as a whole. No PEX19-specific natural-history cohort, randomized trial, standardized quality-of-life analysis, single-cell/spatial study or validated prognostic biomarker is available in the retrieved evidence. | Case-count and cohort limitations (pqac-00000001, pqac-00000003, pqac-00000004); current study scope (pqac-00000029, pqac-00000032) |


*Table: Compact evidence map separating findings demonstrated in PEX19-associated PBD12A from broader Zellweger-spectrum extrapolations. It highlights the exceptionally small human case base and consequent limits on frequencies, prognosis and treatment inference.*