| Domain | High-confidence finding | Quantitative evidence | Evidence type/source |
|---|---|---|---|
| Disease/gene identity | MMDS1 is an autosomal-recessive mitochondrial iron–sulfur-cluster maturation disorder caused by biallelic **NFU1** variants; identifiers include **MONDO:0011582** and **OMIM 605711**. | More than 35 affected individuals had been reported worldwide by 2021. | Aggregated disease-target evidence and systematic review (pqac-00000000, pqac-00000005, pqac-00000022) |
| Severe infantile phenotype | Classical MMDS1 causes neonatal/infantile encephalopathy with hypotonia, feeding failure, respiratory disease, neurologic regression, and early death. | In one seven-patient cohort, **6/7** died within 6 months; an earlier 20-patient summary recorded **20/20 deaths**. | Human clinical cohort and literature review (pqac-00000001, pqac-00000021) |
| Milder NFU1–HSP continuum | Hypomorphic biallelic missense variants can cause pure or complex hereditary spastic paraplegia with longer survival, demonstrating broader expressivity than classical MMDS1. | **19** individuals from **10** families: HSP-predominant disease in **16/19** and neurodevelopmental delay with severe hypotonia in **3/19**. | Multicenter human cohort (pqac-00000008, pqac-00000020) |
| Diagnostic biomarkers | Elevated lactate and glycine, reduced pyruvate-dehydrogenase activity, and respiratory-chain defects—especially complexes I and II—are important biochemical clues but are not individually specific. | Ahting cohort: elevated lactate **5/6**, elevated glycine **7/7**, PDH deficiency **5/5**, and complex I/II+III defects **4/5** tested. | Human biochemical cohort (pqac-00000001) |
| MRI | Typical imaging shows symmetric progressive or cavitating white-matter disease; basal-ganglia, thalamic, brainstem, spinal-cord, and corpus-callosum abnormalities may occur. White-matter disease also accompanies milder NFU1-HSP. | White-matter abnormalities were present in all members of the reported 19-person NFU1-continuum cohort. | Human MRI cohorts and systematic review (pqac-00000002, pqac-00000018, pqac-00000020) |
| Core mechanism | Defective NFU1-mediated **[4Fe–4S]** delivery compromises LIAS and selected respiratory proteins, reducing protein lipoylation and impairing PDH, α-ketoglutarate dehydrogenase, glycine cleavage, and oxidative phosphorylation. | ISCU2 and ISCA1 donate clusters to NFU1; FDX2 assists formation of its bridging [4Fe–4S] cluster. | Biochemical/cellular mechanistic study supported by patient biochemistry (pqac-00000004, pqac-00000001) |
| Pulmonary hypertension | Pulmonary arterial hypertension is a major, sometimes fatal MMDS1 manifestation, particularly reported with **p.Gly208Cys**. A humanized NFU1 rat reproduced pulmonary vascular remodeling and sex-biased susceptibility. | PAH was estimated in approximately **70%** of reported Gly208Cys-associated cases; penetrance was greater in female than male mutant rats. | Human case synthesis and CRISPR rat model (pqac-00000010, pqac-00000019) |
| Treatment/trials | No approved disease-modifying treatment or MMDS1-specific interventional trial was identified; documented care is supportive, including respiratory, nutritional, cardiac/pulmonary, neurologic, rehabilitative, and palliative management. | Registry search returned **no relevant MMDS1 interventional trial**; severe published cases received measures such as artificial ventilation and palliative care. | Trial-registry search and human clinical reports (pqac-00000018, pqac-00000022) |
| Key 2023 development: translation | NFU1-mutant patient fibroblasts revealed previously unrecognized attenuation of mitochondrial protein synthesis; the proposed route is ISCA1–NFU1 delivery of a [4Fe–4S] cluster to METTL17 during small mitoribosomal-subunit assembly. | No NFU1-specific clinical effect size reported. | Patient-derived fibroblasts and mechanistic cell studies, published October 2023 (pqac-00000011) |
| Key 2023 development: neuromuscular signaling | Patient-specific *C. elegans* NFU1 variants caused allele-dependent cholinergic dysfunction: Gly147Arg produced acetylcholine hypersensitivity rescued by reducing acetylcholine release, whereas Gly166Cys predominantly caused postsynaptic hypersensitivity. | Reducing acetylcholine release rescued nearly all measured Gly147Arg neuromuscular phenotypes. | CRISPR *C. elegans* model, published February 2023; therapeutic relevance remains preclinical (pqac-00000015, pqac-00000016) |


*Table: Concise synthesis of established clinical, biochemical, mechanistic, and model-system evidence for NFU1-related MMDS1, including quantitative cohort findings and major 2023 advances.*