| Year | Citation (first author, journal) | Study type (review/case series/mechanistic) | Key contributions for BNS (definition/triad; cohort size; key stats like NTE activity means/thresholds; diagnostic insights) | URL/DOI | Notes (PMID if known—leave blank if not present in text) |
|---|---|---|---|---|---|
| 2024 | Liu, *Brain* | Mechanistic + cohort + systematic review | PNPLA6 disorders placed on a continuous spectrum including Boucher–Neuhäuser syndrome (BNHS). Cohort: 23 new patients + 95 previously reported individuals. Functional assay measured 46 disease-associated and 20 common variants; 36 variants reclassified as pathogenic and 10 as likely pathogenic. Synthetic residual NTE activity differed by phenotype: SPG39 mean ~51% (n=12) vs BNHS ~28% (n=19) and OMCS/LNMS ~28% (n=26); lower activity associated with retinopathy/endocrinopathy, with reported threshold-type observations for endocrine/ophthalmic disease below ~32% and retinal degeneration around 40–50% residual activity; mouse data supported retinopathy threshold and embryonic lethality below 40% activity. Supports NTE activity as a biomarker for therapeutic trials. (pqac-00000008, pqac-00000011, pqac-00000014, pqac-00000015) | https://doi.org/10.1093/brain/awae055 |  |
| 2023 | Liu, *Ophthalmic Genetics* | Review | Defines five PNPLA6 disorders, including Boucher–Neuhäuser syndrome. States PNPLA6/NTE is involved in phospholipid homeostasis and trafficking; animal and cellular models support loss-of-function. As of May 2023, 95 published individuals with biallelic PNPLA6 variants. Cerebellar atrophy/ataxia reported in up to ~90% of cases. BNHS distinguished from Gordon–Holmes by added chorioretinal dystrophy. Diagnostic insights: neurological imaging for cerebellar atrophy, ERG/retinal imaging/visual fields for chorioretinal dystrophy, hormonal testing for anterior hypopituitarism, and exam for hair anomalies. (pqac-00000029, pqac-00000030, pqac-00000034) | https://doi.org/10.1080/13816810.2023.2254830 |  |
| 2024 | Liampas, *Molecular Biology Reports* | Case reports | Two siblings with a novel homozygous PNPLA6 missense variant. Reiterates classical BNS triad: hypogonadotropic hypogonadism, spinocerebellar ataxia, and chorioretinal dystrophy; notes peripheral axonal neuropathy can occur. Provides temporal guidance: HH often in first two decades; ataxia usually before early adulthood but can be late; chorioretinal dystrophy usually before age 50 and may progress to severe visual loss/blindness. Diagnostic workup included MRI, ophthalmologic assessment, endocrine evaluation, electrophysiology, WES and Sanger segregation. (pqac-00000001, pqac-00000023) | https://doi.org/10.1007/s11033-024-09515-4 |  |
| 2022 | He, *Frontiers in Genetics* | Case report + variant analysis/systematic review | Defines BNS as a rare autosomal recessive PNPLA6 disorder with the triad of cerebellar ataxia, chorioretinal dystrophy, and hypogonadotropic hypogonadism; gives MIM 215470. Reports a 17-year-old with progressive night blindness from age 4, primary amenorrhea, absent secondary sexual development, retinal pigmentary degeneration, and CHH without current ataxia. Identified compound heterozygous PNPLA6 variants by WES; RT-PCR showed reduced PNPLA6 mRNA. Diagnostic insight: detailed ophthalmic exam, endocrine panels, pituitary/pelvic imaging, bone age X-ray, WES/Sanger; authors note gene sequencing is currently the primary diagnostic method. (pqac-00000000, pqac-00000020) | https://doi.org/10.3389/fgene.2022.810537 |  |
| 2022 | Nanetti, *Frontiers in Neurology* | Case series + literature review | Reviews age-dependent PNPLA6 phenotypes and includes BN presentations. Across eight new PNPLA6 cases: 7/8 had cerebellar ataxia, 5/8 hypogonadotropic hypogonadism, 2/8 chorioretinal dystrophy; cerebellar symptoms mean onset 31 years (range 9–55) with very slow progression. Notes early-onset presentations may start with chorioretinal dystrophy, juvenile cases with HH, adult cases with ataxia. MRI may show cerebellar atrophy (often superior/dorsal vermis) and severe cerebellar atrophy in BN cases. Recommends multidisciplinary assessment and PNPLA6 screening in late-onset/cANVAS-like ataxia when RFC1 expansions are absent. (pqac-00000002, pqac-00000005, pqac-00000021, pqac-00000026) | https://doi.org/10.3389/fneur.2021.793547 |  |
| 2019 | O’Neil, *Ophthalmic Genetics* | Deep phenotyping case report | Shows that PNPLA6-associated BNS may present with predominantly retinal findings and subtle systemic abnormalities, mimicking choroideremia. Ophthalmic workup included SD-OCT, ERG, kinetic fields, autofluorescence imaging; systemic confirmation came from hypogonadotropic hypogonadism and cerebellar vermis hypoplasia on MRI. Highlights the need to consider PNPLA6/BNS in diffuse chorioretinal atrophies and to combine ophthalmic phenotyping with systemic review and genetic testing. (pqac-00000007) | https://doi.org/10.1080/13816810.2019.1605392 |  |
| 2014 | Deik, *Journal of Neurology* | Case report + genetics | Landmark report confirming compound heterozygous PNPLA6 mutations as a cause of BNS with late-onset ataxia. Uses MIM #215470 for BNS and emphasizes the triad of autosomal recessive cerebellar ataxia, hypogonadotropic hypogonadism, and chorioretinal dystrophy. Diagnostic workup included fundoscopy/OCT, ERG, visual fields, endocrine testing (low LH/FSH), brain MRI showing superior cerebellar/vermian atrophy, EMG/NCS showing mild distal axonal neuropathy, and PNPLA6 sequencing. Also notes possible cognitive involvement and subclinical polyneuropathy. (pqac-00000003, pqac-00000004, pqac-00000019) | https://doi.org/10.1007/s00415-014-7516-3 |  |
| 2022 | Kretzschmar, *Metabolites* | Mechanistic review | Reviews PNPLA6/NTE as an evolutionarily conserved phospholipase first linked to organophosphate-induced delayed neuropathy and later to inherited disorders including BNS. Summarizes normal role in lipid homeostasis and model-system evidence: mouse brain conditional knockout causes age-related neurodegeneration, complete knockout is embryonic lethal, and Drosophila *swiss-cheese* loss causes progressive locomotor defects and neurodegeneration. Useful for mechanistic context underlying BNS/PNPLA6 loss-of-function. (pqac-00000031) | https://doi.org/10.3390/metabo12040284 |  |


*Table: This table summarizes the most useful recent and foundational sources for Boucher–Neuhäuser syndrome within the broader PNPLA6 disorder spectrum. It highlights how each paper contributes evidence on definition, genotype–phenotype correlations, diagnostics, and mechanistic understanding.*