| Domain | Best-supported finding | Evidence scope/strength | Key identifiers or quantitative details |
|---|---|---|---|
| Entity and gene | A severe congenital Mendelian disorder caused by biallelic **PI4KA** variants and defined by perisylvian polymicrogyria, cerebellar hypoplasia, and arthrogryposis. | Curated disease–gene association plus primary human familial evidence. (pqac-00000003, pqac-00000018) | **OMIM 616531**; **MONDO:0014679**; PI4KA/ENSG00000241973; PMID **25855803**. |
| Original cohort | Three affected female fetuses occurred in one nonconsanguineous European-ancestry family; three additional early miscarriages were reported. | Single-family case series; strong segregation but very small ascertainment base. (pqac-00000008, pqac-00000009) | Pregnancy terminations at **34, 28, and 16 gestational weeks**. |
| Causal variants | All three fetuses were compound heterozygous for a paternal stop-gain and maternal catalytic-domain missense variant. | Segregation confirmed by Sanger sequencing; missense effect supported experimentally. (pqac-00000003, pqac-00000011, pqac-00000015) | **NM_058004.3:c.2386C>T, p.(Arg796Ter)** and **c.5560G>A, p.(Asp1854Asn)**; germline, autosomal recessive. |
| Cardinal brain phenotype | Bilateral perisylvian polymicrogyria and cerebellar hypoplasia/dysplasia were present in all three reported fetuses. | Prenatal MRI and fetal neuropathology; **3/3**, but frequencies are family-specific rather than population estimates. (pqac-00000008, pqac-00000015) | PMG **3/3 (100%)**; cerebellar hypoplasia/dysplasia **3/3 (100%)**; abnormal vermis/dentate nuclei also described. |
| Cardinal musculoskeletal phenotype | Congenital arthrogryposis/joint contractures with bilateral talipes equinovarus and externally rotated hips occurred in all three fetuses. | Direct fetal examination/pathology; **3/3** in the original family. (pqac-00000008) | Arthrogryposis/contractures **3/3 (100%)**; bilateral talipes equinovarus **3/3 (100%)**; flexed knees and wrist contracture varied. |
| Other congenital findings | Micrognathia was consistent; variable findings included dolichocephaly, ventriculomegaly, small pons, dysplastic olivary nuclei, renal pelviectasis, and mild/borderline pulmonary hypoplasia. | Patient-level fetal observations; frequencies generally limited to the three-family cohort. (pqac-00000008) | Micrognathia **3/3 (100%)**; normal muscle histology argues against a primary myopathy in this family. (pqac-00000015) |
| Inheritance and recurrence | The disorder follows autosomal-recessive inheritance; heterozygous carriers are considered asymptomatic. | Strong intrafamilial segregation and broader PI4KA disease curation. (pqac-00000019, pqac-00000021) | If both parents are carriers: **25% affected, 50% carrier, 25% neither variant** per pregnancy. |
| Biochemical mechanism | PI4KA/PI4KIIIα generates plasma-membrane phosphatidylinositol-4-phosphate needed to sustain PI(4,5)P₂ and downstream membrane signaling. p.Asp1854Asn abolishes detectable catalytic activity in vitro. | Direct COS-7 biochemical assay for p.Asp1854Asn; downstream developmental chain remains inferred. (pqac-00000011, pqac-00000013, pqac-00000014) | Mutant and wild-type protein abundance was comparable in the assay; activity of p.Asp1854Asn was indistinguishable from negative controls. p.Arg796Ter protein function was not directly tested. |
| Broader PI4KA spectrum | Other biallelic PI4KA genotypes produce a continuum from severe developmental encephalopathy, hypomyelination, structural brain abnormalities, immune/GI disease, and contractures to pure hereditary spastic paraplegia. | Ten-patient multicenter cohort plus later case reports; informative for gene-level disease but not equivalent to the narrowly defined 616531 phenotype. (pqac-00000004, pqac-00000006, pqac-00000024) | In the 2021 cohort, **10 unrelated patients** were reported; one additional p.Asp1854Asn-homozygous patient had bilateral perisylvian PMG. |
| Diagnosis | Diagnosis rests on compatible prenatal/postnatal neuroimaging and contractures plus identification of biallelic pathogenic/likely pathogenic PI4KA variants with parental segregation. | Expert disease review supported by primary exome-sequencing discovery. (pqac-00000003, pqac-00000019) | Fetal ultrasound/MRI; postnatal brain MRI when applicable; multigene panel, WES, or WGS with CNV analysis. PI4KAP1/PI4KAP2 pseudogenes require assay-specific validation. A VUS alone is not diagnostic. |
| Treatment and trials | No disease-modifying therapy is established; management is manifestation-directed and multidisciplinary. No relevant interventional trial was identified in the retrieved ClinicalTrials.gov search. | Expert management recommendations extrapolated from the broader PI4KA spectrum; no syndrome-specific treatment trial or response-rate evidence. (pqac-00000019, pqac-00000022) | PT/OT, mobility and communication aids, standard antiseizure therapy, spasticity treatment, feeding support/gastrostomy, and indicated GI, immune, hearing, and vision care. Leflunomide remains investigational. |
| Epidemiology and prognosis gaps | Population prevalence, incidence, penetrance, sex ratio, survival, life expectancy, quality-of-life scores, and prognostic biomarkers have not been established for the specific syndrome. | Evidence is inadequate because the defining report comprised only three terminated pregnancies in one family. (pqac-00000008, pqac-00000020) | The observed **3/3** phenotype frequencies must not be interpreted as general-population penetrance estimates; no live-born natural-history cohort exists for the narrowly defined disorder. |


*Table: Knowledge-base summary of the defining PI4KA-associated fetal syndrome, separating direct evidence from the original family from findings across the broader PI4KA-related disorder spectrum. It highlights quantitative observations and major diagnostic, therapeutic, epidemiologic, and prognostic gaps.*