| domain | best quantitative finding | interpretation | source/date/DOI or PMID if available |
|---|---:|---|---|
| Neonatal cohort size | 24 neonatal-onset cases total (4 new + 20 literature cases) | Best current neonatal-focused summary of COQ4 disease burden is still based on small case aggregation, underscoring rarity and likely ascertainment bias (pqac-00000001) | Pan et al., *Front Pediatr* (Sep 2024), doi:10.3389/fped.2024.1410133 |
| Neonatal mortality/survival | Mean survival 60.0 ± 98.0 days; mortality 75% in Chinese cases (9/12) and 91.7% in non-Chinese cases (11/12), P=0.27 | Neonatal COQ4 disease has very poor short-term survival overall, with no statistically significant regional mortality difference in this review (pqac-00000001) | Pan et al., *Front Pediatr* (Sep 2024), doi:10.3389/fped.2024.1410133 |
| Neonatal biochemical abnormality | Hyperlactatemia in 75% (18/24) | Elevated lactate is common and useful diagnostically, but not universal; absence of lactate elevation does not exclude disease (pqac-00000001) | Pan et al., *Front Pediatr* (Sep 2024), doi:10.3389/fped.2024.1410133 |
| Neonatal genetic diagnosis | 20/24 diagnosed by whole-exome sequencing | WES is the dominant real-world diagnostic route for neonatal COQ4 disease (pqac-00000001) | Pan et al., *Front Pediatr* (Sep 2024), doi:10.3389/fped.2024.1410133 |
| Prenatal risk signals | Prenatal abnormalities more frequent in preterm than full-term infants: 66.7% vs 16.7%, P=0.02 | Supports prenatal/perinatal disease onset in the severest neonatal presentations (pqac-00000001) | Pan et al., *Front Pediatr* (Sep 2024), doi:10.3389/fped.2024.1410133 |
| Largest human cohort | 44 individuals from 36 families; 23 variants identified | COQ4 deficiency is clinically heterogeneous but now sufficiently characterized to define subtypes (pqac-00000002, pqac-00000012) | Laugwitz et al., *J Med Genet* (Oct 2022), doi:10.1136/jmedgenet-2021-107729 |
| Core phenotype frequencies | Respiratory distress 24/34; feeding difficulties 20/28; hypertrophic cardiomyopathy 15/35; hyperlactataemia 22/31 | Multisystem neonatal/infantile disease commonly affects brain, cardiorespiratory status, feeding, and metabolism (pqac-00000004) | Laugwitz et al., *J Med Genet* (Oct 2022), doi:10.1136/jmedgenet-2021-107729 |
| Neuroimaging frequencies | Cerebral atrophy 18 patients; cerebellar atrophy 15/36; cerebellar hypoplasia 10 cases; stroke-like lesions 8 patients; delayed myelination in ~50% of MRI studies | Neuroimaging often shows a mitochondrial encephalopathy pattern, with cerebellar involvement especially prominent in severe neonatal disease (pqac-00000004, pqac-00000006) | Laugwitz et al., *J Med Genet* (Oct 2022), doi:10.1136/jmedgenet-2021-107729 |
| Clinical subtypes | 3 patterns: type 1 neonatal brain anomalies/epileptic encephalopathy; type 2 stroke-like lesions; type 3 moderate stable disease | Helps stratify prognosis: type 1 is most severe and often neonatal, type 3 relatively milder (pqac-00000002, pqac-00000006) | Laugwitz et al., *J Med Genet* (Oct 2022), doi:10.1136/jmedgenet-2021-107729 |
| Survival in broader cohort | Only 5/44 reached adulthood | Confirms high childhood mortality, especially in early-onset encephalopathic forms (pqac-00000000, pqac-00000010) | Laugwitz et al., *J Med Genet* (Oct 2022), doi:10.1136/jmedgenet-2021-107729 |
| Treatment exposure and response | CoQ10 given to 29 patients at 15–60 mg/kg/day; 16/29 no response; 12/29 limited improvement/stabilization | Oral CoQ10 is widely used in practice but usually yields modest or absent neurologic benefit in COQ4 disease (pqac-00000004, pqac-00000011) | Laugwitz et al., *J Med Genet* (Oct 2022), doi:10.1136/jmedgenet-2021-107729 |
| Current treatment recommendation | Oral CoQ10 should be started immediately in suspected CoQ biosynthesis disorders and titrated to at least 30 mg/kg/day after genetic confirmation; one COQ4 case also received idebenone 20 mg/kg/day | Expert practice favors early empiric high-dose CoQ10 despite limited evidence for reversing advanced neonatal neurodegeneration (pqac-00000007) | Wahedi et al., *Neurol Genet* (Dec 2024), doi:10.1212/NXG.0000000000200209 |
| Cellular mechanism | Patient fibroblasts: reduced cellular CoQ10 in most lines; elevated 6-demethoxyubiquinone (6-DMQ); severe galactose-growth defect with partial rescue by CoQ10 | Strong in vitro evidence that COQ4 variants impair CoQ biosynthesis and mitochondrial energy metabolism; exogenous CoQ10 only partially corrects the defect (pqac-00000005, pqac-00000013) | Laugwitz et al., *J Med Genet* (Oct 2022), doi:10.1136/jmedgenet-2021-107729 |
| Protein-level mechanism | COQ4 protein reduced in patient fibroblasts, often with secondary reductions in COQ7/COQ9 | Supports the model that COQ4 helps stabilize the CoQ biosynthetic complex (Q-synthome), so deficiency destabilizes the pathway beyond a single enzymatic step (pqac-00000005, pqac-00000011, pqac-00000015) | Laugwitz et al. 2022; Xie et al., *Front Genet* (Jan 2022), doi:10.3389/fgene.2021.776807 |


*Table: This table condenses the strongest quantitative evidence for COQ4-related neonatal encephalomyopathy across neonatal case aggregation, the largest human cohort, current treatment practice, and cellular mechanism studies. It is useful for rapidly extracting disease severity, diagnostic yield, treatment response, and mechanistic support from the available literature.*