Bone Marrow Failure Syndrome 4 (MYSM1 Deficiency) — Comprehensive Research Report

1. Disease Information

Overview. Bone Marrow Failure Syndrome 4 (BMFS4) is an ultra-rare, autosomal recessive inherited bone marrow failure syndrome (IBMFS) caused by biallelic loss-of-function variants in MYSM1. It combines early-onset, progressive, often initially transient/fluctuating bone marrow failure (anemia, leukopenia/neutropenia, mild thrombocytopenia, myelodysplastic marrow features) with a B-cell– and NK-cell–predominant immunodeficiency and a constellation of non-hematologic developmental anomalies (skeletal dysplasia, cataracts, facial dysmorphism, short stature, cerebral hypoplasia/neurodevelopmental delay). It was first reported in 2013 as an apparently novel IBMFS in a consanguineous Saudi family (Alsultan et al., Blood 2013;122:3844–3845, PMID:24288411), and clinically delineated as a distinct syndrome by Bahrami et al. in 2017.

Key identifiers: - MONDO: MONDO:0020856 — label "bone marrow failure syndrome 4"; xrefs OMIM:618116, GARD:0025264, MedGen:C4748257/1648485 (confirmed via OLS lookup) - OMIM: #618116 BONE MARROW FAILURE SYNDROME 4; BMFS4 (phenotype), caused by variants in MYSM1 (612176) - Orphanet: ORPHA:508542 — "Congenital progressive bone marrow failure–B-cell immunodeficiency–skeletal dysplasia syndrome" — autosomal recessive, neonatal onset, prevalence <1/1,000,000 - GARD: 0025264 / GARD disease page 22071 (same synonym as Orphanet) - Gene: MYSM1, HGNC:29401, NCBI Gene 114803, chromosome 1p32.1 (GRCh38: 1:58,654,743–58,700,062); mouse ortholog Mysm1, MGI:2444584 - ICD-10/11:* No dedicated code identified; would fall under D61.0-series (constitutional aplastic anemia) / QA-type rare-disease codes generically

Synonyms: BMFS4; MYSM1 deficiency; MYSM1-related bone marrow failure syndrome; Congenital progressive bone marrow failure, B-cell immunodeficiency, skeletal dysplasia syndrome.

Evidence basis: The disease-level evidence base is overwhelmingly aggregated case-report and small-case-series literature (individual patients and consanguineous sibships, largely of Middle Eastern/consanguineous ancestry) rather than large cohort registries — fewer than ~20–25 molecularly confirmed patients have been published to date across all reports, consistent with Orphanet's "<1/1,000,000" prevalence class and OMIM's description of "only three pathogenic variants... reported in nine patients" as of the 2020 Li et al. report (PMID:32640305), a number that has since grown modestly with additional case reports through 2025.

2. Etiology

Disease causal factor: BMFS4 is a monogenic, purely genetic disease — biallelic (homozygous or compound heterozygous) loss-of-function variants in MYSM1 (encoding the histone H2A deubiquitinase MYSM1/2A-DUB). No environmental, infectious, or purely mechanistic non-genetic cause is described; the disorder is congenital and the causal lesion is present from conception.

Genetic risk factors: - Biallelic MYSM1 variants are necessary and sufficient. Reported classes: nonsense/premature-stop (p.E390, p.R478, p.Y489), missense (p.H656R, disrupting the JAMM/MPN catalytic domain), and a cryptic synonymous splice variant (c.399G>A, p.L133L) shown experimentally to cause exon 6 skipping and a frameshift/premature stop (Li et al. 2020, PMID:32640305: "the c.399G>A variant leads to exon 6 skipping, resulting in a premature termination codon (c.321_399del, p.V108Lfs13)"; the trans allele c.1467C>G, p.Y489 "triggered nonsense-mediated mRNA degradation"). - Consanguinity is a strong enabling risk factor for exposing this rare recessive allele — nearly every published pedigree (Saudi Arabian, other Arab, Chinese with parental consanguinity noted in several reports) involves consanguineous unions, consistent with an autosomal recessive, population-founder-type distribution rather than a pan-ethnic common disease. - No modifier genes have been formally established in humans; in mice, genetic interaction with Trp53 (p53) is the dominant modifier axis (see Mechanism, below) — Belle et al. 2015 (PMID:25710881) showed Mysm1⁻/⁻p53⁻/⁻ double-knockout mice have "full rescue of Mysm1⁻/⁻ developmental and hematopoietic defects... including restoration of lymphopoiesis, and HSC numbers and functions", formally implicating p53 hyperactivation as the proximate driver of the hematopoietic phenotype — a strong candidate modifier axis for human disease severity, though not yet tested clinically. - Population genetics: gnomAD data indicate MYSM1 is not* constrained for heterozygous loss-of-function (pLI ≈ 0.09, LOEUF ≈ 0.58), consistent with a purely recessive human disease mechanism and with carrier heterozygotes being clinically unaffected (as in the original Alsultan family, where heterozygous parents were unaffected carriers).

Environmental risk/gene-environment factors: None established as disease-causal. However, MYSM1-deficient cells show heightened DNA-damage/genotoxic stress sensitivity (Bahrami et al. 2017, PMID:28115216: affected cells showed "heightened vulnerability to DNA-damaging agents, sustained p38 activation, elevated oxidative stress, and diminished survival following UV exposure"), which is mechanistically relevant to treatment planning (radiosensitivity should be considered in conditioning-regimen and radiologic-exposure decisions) rather than to primary disease causation.

Protective factors: None specifically described. Loss of p53 function is protective against the hematopoietic phenotype in the mouse model (see above) but this is a laboratory finding, not a clinical protective factor (and constitutive p53 loss would itself predispose to malignancy, which is directly relevant given the documented TP53-mutant clonal evolution in human BMFS4, see §8/§11 below).

3. Phenotypes

Frequencies below are qualitative (derived from aggregated small case series; formal Orphanet HPO-frequency annotation was not accessible during this research pass, so frequencies are described narratively rather than as precise percentages except where a source states them).

Hematologic (laboratory abnormalities — very frequent, near-universal)

Anemia, often severe, transfusion-dependent, presenting in infancy (as early as 1 month to ~15 months of age); HP:0001903 Anemia. Onset: neonatal–infantile. Course: can show a striking pattern of transfusion dependence for years followed by spontaneous partial recovery, then later relapse/progression (PMC12176283: Case 1 "remained transfusion-dependent till the age of 10 years, followed by a phase of spontaneous recovery").
Leukopenia/neutropenia — HP:0001882/HP:0001875.
Mild-to-moderate thrombocytopenia — HP:0001873 (typically milder than the anemia/neutropenia, distinguishing it somewhat from classic amegakaryocytic thrombocytopenia syndromes).
Bone marrow hypocellularity with myelodysplastic features — HP:0005528 (Bone marrow hypocellularity), dysplastic erythroid and myeloid precursors; marrow cellularity as low as 5–20% reported (PMC12176283).
Pancytopenia develops over time in a substantial fraction of patients.
Some patients are initially misdiagnosed as Diamond-Blackfan anemia (macrocytic, erythroid-predominant marrow failure) before the immunologic/skeletal/genetic picture clarifies the diagnosis (PMC12176283, Cases 3–4).

Immunologic (very frequent)

B-cell deficiency/lymphopenia — HP:0010976 (Decreased circulating total B cell count).
Hypogammaglobulinemia and impaired antibody response to vaccination — HP:0004313 (Decreased circulating antibody level), HP:0002846 (Abnormal B cell count is a coarse fallback if antibody-response term unavailable).
NK-cell deficiency/dysfunction — reported in multiple cases (e.g., Li et al. 2020, PMID:32640305, describes "B-cell and natural killer cell deficiency in the peripheral blood").
Recurrent infections, especially upper respiratory tract infections in early childhood, often manageable with prophylactic antibiotics — HP:0002205/HP:0011947.

Skeletal/craniofacial (frequent)

Short stature — HP:0004322.
Rhizomelic shortening of the arms / short humerus — HP:0008843/related UBERON:humerus-associated HPO terms.
Brachydactyly / short metacarpals / short fingers — HP:0009826, HP:0010049.
Thoracic asymmetry, trigonocephaly — HP:0000268 (Trigonocephaly).
Midface hypoplasia/retrusion, coarse facial features, low-set ears — HP:0011800 / HP:0000278 / HP:0000369.
Gingival hyperplasia and delayed dentition — HP:0000212 / HP:0000696.

Ophthalmologic

Cataracts — HP:0000518 (frequent, reported across multiple case series, e.g., Bahrami et al. 2017).

Neurologic/developmental

Neurodevelopmental delay/intellectual disability — HP:0012758/HP:0001249.
Decreased cerebral volume on brain imaging (cerebral hypoplasia) — HP:0006872-adjacent (Reduced cerebral cortical volume) or HP:0002119 (Ventriculomegaly)-type imaging findings; GARD lists "cerebral hypoplasia" explicitly.
Sensorineural hearing loss reported.

Dermatologic

Dry skin and eczema — HP:0000958 (Dry skin), HP:0000964 (Eczema).

Cardiac/renal

Cardiac anomalies including congestive heart failure reported in some patients; renal anomalies mentioned in some syndromic descriptions (less consistently reported than the core hematologic/immunologic/skeletal triad).

Severity/progression pattern

Bahrami et al. (PMID:28115216) summarize the core syndrome as: "progressive bone marrow failure associated with myelodysplastic features, immunodeficiency affecting B cells and neutrophil granulocytes, and complex developmental aberrations" — establishing progression (not static severity) and multi-system involvement as defining features. Expressivity is variable: a 2024 report (Sakovich et al., J Clin Immunol, describing an adult patient with a novel MYSM1 variant) documents a milder, later-recognized adult phenotype, indicating a broader clinical spectrum than the classic severe pediatric presentation.

Quality-of-life impact: Not formally measured with validated instruments (EQ-5D/SF-36) in the literature reviewed; qualitatively, chronic transfusion dependence, recurrent infection, developmental delay, and eventual HSCT (with its own morbidity, e.g., GVHD) constitute substantial disease burden, particularly given transformation risk to myeloid malignancy in later childhood/adolescence (see §11).

4. Genetic/Molecular Information

Causal gene: MYSM1 (Myb-like, SWIRM and MPN domains 1), HGNC:29401, OMIM *612176, chromosome 1p32.1, NCBI Gene ID 114803.

Protein: 828-amino-acid nuclear (and, as recently characterized, also cytosolic-pool) chromatin-binding transcriptional cofactor/deubiquitinase. Domain architecture (per multiple reviews, e.g., Belle et al./Fiore et al. 2020, Int J Mol Sci, PMID:32344625): - SWIRM domain — compact helix-turn-helix-related fold (5 α-helices), structurally similar to yeast Swi3, implicated in chromatin binding. - SANT domain — structurally similar to the c-MYB DNA-binding domain; binds DNA in vitro. - JAMM/MPN metalloprotease domain — the catalytic domain; a Zn²⁺-dependent JAMM-motif (consensus EXnHSHX₇SX₂D) isopeptidase that hydrolyzes ubiquitin-chain isopeptide bonds; the residue Asp567 within this domain is required for catalytic (deubiquitinase) activity toward histone H2A.

Reported pathogenic variant classes (all biallelic; no dominant/heterozygous disease reported): | Variant | Type | Report | |---|---|---| | p.E390 | Nonsense | Original/early cohort (cited across multiple papers, e.g., PMID:32640305) | | p.R478 | Nonsense | Original/early cohort | | p.H656R | Missense (JAMM domain) | Original/early cohort | | p.Y489 | Nonsense (compound het.) | Li et al. 2020, PMID:32640305 | | c.399G>A (p.L133L), synonymous, causes exon 6 skipping → p.V108Lfs13 | Cryptic splice | Li et al. 2020, PMID:32640305 — "first report of a synonymous splicing variant that induces post-transcriptional skipping of exon 6" | | Homozygous premature stop codon | Nonsense | Bahrami et al. 2017, PMID:28115216 (two siblings) | | Additional compound-heterozygous variants | Various | Huang et al. 2021 (PMID:33858043, Chinese infant), Zhan et al. 2021 (PMID:33618624) |

As of 2020, OMIM/Li et al. state that "only three pathogenic variants (E390, R478, and H656R) of MYSM1 have been reported in nine patients, and all variants are homozygous" — the mutational spectrum has since expanded with compound-heterozygous and splice-altering alleles, indicating the variant catalog remains small and incompletely characterized (few if any entries in ClinVar with robust multi-submitter classification; formal ACMG/AMP tiering not systematically published for most alleles beyond the original case reports).

Functional consequence: All reported alleles are loss-of-function (null or catalytically dead), consistent with a simple LOF/haploinsufficiency-is-not-sufficient (i.e., strictly biallelic-LOF-required) disease mechanism — heterozygous carriers (parents) are unaffected in every reported pedigree, and population data (gnomAD pLI ≈ 0.09) support tolerance of monoallelic loss.

Somatic vs. germline: The primary disease-causing variants are germline. However, secondary somatic clonal evolution is a well-documented late feature: Haroon et al. 2025 (PMID:40535318) report acquired somatic CALR p.(P228S) (VAF 50%), monosomy 5q (EGR1 loss), TP53 mutation, monosomy 7, and trisomy 8 arising during transformation to MDS/AML in BMFS4 patients — i.e., BMFS4 marrow is itself a pre-leukemic clonal-evolution substrate, analogous to other IBMFS (Fanconi anemia, Shwachman-Diamond syndrome, SAMD9/SAMD9L disorders).

Modifier genes: No confirmed human modifiers; Trp53 is the dominant genetic modifier identified in the mouse model (Belle et al. 2015, PMID:25710881).

Epigenetic information: MYSM1 is itself a direct epigenetic regulator — it deubiquitinates monoubiquitinated histone H2A at Lys119 (H2AK119ub, GO:0033558 protein deubiquitination / more specifically histone H2A deubiquitination), a repressive chromatin mark; loss of MYSM1 catalytic activity is predicted to cause aberrant retention of H2AK119ub and dysregulated gene expression at MYSM1 target loci, including ribosomal protein genes (Belle et al. 2020, PMID:32641579) and the NK-lineage gene Id2 (Nandakumar et al. 2013, PMID:24062447) and the B-lineage gene Pax5 (Jiang et al. 2015, Sci Rep, PMC4562257).

Chromosomal abnormalities: None reported as a primary/germline disease mechanism for BMFS4 (this is a point-mutation/small-indel disease, not a microdeletion/CNV syndrome); acquired chromosomal abnormalities (monosomy 5, monosomy 7, trisomy 8) occur secondarily as leukemic clonal evolution (see above and §11).

5. Environmental Information

No primary environmental, toxin, occupational, or lifestyle causal factors are described for BMFS4 — it is a fully penetrant monogenic recessive disorder present from birth. The one environment-adjacent mechanistic finding is cellular genotoxic/oxidative stress hypersensitivity: Bahrami et al. (PMID:28115216) demonstrated that MYSM1-deficient patient cells show "heightened vulnerability to DNA-damaging agents, sustained p38 activation, elevated oxidative stress, and diminished survival following UV exposure." This has practical (not etiologic) relevance: it argues for minimizing unnecessary genotoxic exposures (radiation, certain chemotherapeutics) in affected patients and for reduced-intensity/radiation-sparing conditioning in transplant, rather than implicating environmental exposure in disease causation.

No infectious trigger or agent is implicated in BMFS4 onset; recurrent infections in affected children are a consequence of the immunodeficiency (B-cell/NK-cell/neutrophil defects), not a cause of the marrow failure.

6. Mechanism / Pathophysiology

Causal chain (ordered, with inference flags)

Biallelic loss-of-function MYSM1 variant (germline, nonsense/missense/cryptic-splice) → loss or inactivation of MYSM1 histone H2A deubiquitinase catalytic activity. (Demonstrated directly — human genetics + in vitro functional studies, e.g., PMID:32640305.)
Loss of MYSM1 deubiquitinase activity leads to failure to remove repressive H2AK119ub marks at target chromatin loci, resulting in dysregulated (reduced) expression of a specific target-gene program, most notably ribosomal protein (RP) genes in hematopoietic stem cells (Belle et al. 2020, PMID:32641579: MYSM1 "maintains ribosomal protein gene expression in hematopoietic stem cells"), and lineage-specific transcription factors including Id2 (NK lineage, PMID:24062447) and Pax5 (B lineage, PMC4562257). (Demonstrated in mouse models; human tissue confirmation is indirect/inferred from phenotypic concordance.)
Reduced ribosomal protein gene expression leads to a ribosomopathy-like state — impaired ribosome biogenesis/protein synthesis in hematopoietic stem and progenitor cells (HSPCs) — directly analogous mechanistically to Diamond-Blackfan anemia and other ribosomopathies, explaining the clinical overlap/misdiagnosis with DBA noted in case series (PMC12176283). (Demonstrated in the mouse model; RP-gene dysregulation shown to be a direct, p53-independent consequence of Mysm1 loss.)
Ribosomal stress/RP-gene dysregulation, together with direct genotoxic/oxidative stress vulnerability of MYSM1-deficient cells, results in activation and elevation of p53 protein across multiple hematopoietic cell types (Belle et al. 2015, PMID:25710881). (Demonstrated — Mysm1⁻/⁻p53⁻/⁻ double-knockout rescue experiment is direct causal evidence in mice.)
Chronic p53 activation leads to impaired hematopoietic stem cell (HSC) self-renewal/function, increased HSC apoptosis and cell-cycle arrest, and results in progressive loss of long-term repopulating HSC capacity. (Demonstrated in mice — full rescue of HSC numbers/function upon p53 co-deletion; human confirmation is inferential from the clinical phenotype of progressive marrow failure.)
Failing HSC output, superimposed on lineage-specific transcriptional defects (reduced Pax5 in B-lineage, reduced Id2/impaired NFIL3 recruitment in NK-lineage), leads to the clinical triad of (a) progressive cytopenias/bone marrow failure with myelodysplastic features, (b) B-cell lymphopenia/hypogammaglobulinemia and NK-cell maturation arrest (immunodeficiency), and (c) — via MYSM1's broader roles in non-hematopoietic tissue differentiation (chromatin regulation is not hematopoiesis-restricted) — the extra-hematopoietic developmental phenotype (skeletal dysplasia, cataracts, craniofacial dysmorphism, cerebral hypoplasia). (The hematologic/immunologic arms are mechanistically well supported; the specific chromatin targets responsible for the skeletal/ocular/craniofacial phenotype are not yet characterized — this link is inferred from MYSM1's role as a general chromatin regulator rather than demonstrated at the target-gene level, and should be flagged as a knowledge gap.)
Persistent replicative/genotoxic stress on a chronically failing, dysplastic marrow leads to, over years (documented range ~9–12 years from initial presentation), acquisition of secondary somatic driver mutations (TP53, CALR) and cytogenetic clonal evolution (monosomy 5/EGR1 loss, monosomy 7, trisomy 8), resulting in transformation to myelodysplastic syndrome (MDS) and/or acute myeloid leukemia (AML) (Haroon et al. 2025, PMID:40535318). (Demonstrated clinically — documented clonal cytogenetic/molecular evolution in a case series; the mechanistic bridge from chronic p53-mediated HSC stress to clonal selection for TP53-mutant escape clones is inferred by analogy to other bone-marrow-failure-to-leukemia trajectories, e.g., Fanconi anemia and SAMD9/9L disorders, rather than directly proven in BMFS4.)

Branch: innate-immune/cytosolic function

In parallel to its nuclear chromatin role, a cytosolic pool of MYSM1 has been characterized as a negative regulator of innate immune signal transduction, promoting deubiquitination of TRAF3, TRAF6, and RIP2 to dampen pattern-recognition-receptor (PRR) signaling (summarized in Fiore/Belle et al. 2020, PMID:32344625). This branch is mechanistically distinct from the hematopoietic/chromatin arm and may contribute to the infection susceptibility phenotype independently of the B/NK-cell lymphopenia, though its direct contribution to human BMFS4 clinical features has not been isolated from the adaptive-immunodeficiency component.

Molecular pathways / processes (suggested ontology terms)

GO:0035522 monoubiquitinated histone H2A deubiquitination (or the general parent GO:0016578 histone deubiquitination) — core MYSM1 catalytic activity
GO:0140853 — (histone H2A deubiquitination-related terms; confirm exact GO ID at curation time via OAK lookup rather than from memory)
GO:0002244 hematopoietic progenitor cell differentiation; GO:0030099 myeloid cell differentiation; GO:0030183 B cell differentiation; GO:0001779 natural killer cell differentiation
GO:0006417 regulation of translation / ribosome biogenesis pathway genes (RP-gene program)
GO:0006977 DNA damage response, signal transduction by p53 class mediator (p53 pathway activation)
GO:0045087 innate immune response (TRAF3/TRAF6/RIP2 axis)

Cell types (Cell Ontology, CL)

CL:0000037 hematopoietic stem cell (primary affected population; site of the p53/ribosomopathy mechanism)
CL:0000816 immature B cell / CL:0000236 B cell (B lymphopoiesis defect)
CL:0000623 natural killer cell (maturation arrest — Id2/NFIL3 axis)
CL:0000771 eosinophil / CL:0000775 neutrophil (neutropenia)
CL:0000037-derived myeloid and erythroid progenitors (dysplastic precursors on marrow biopsy)

(All GO/CL term suggestions should be verified against the current ontology build before binding, per standard curation practice — several exact GO child-term IDs for "histone H2A deubiquitination" specifically were not independently confirmed via OAK in this research pass.)

Molecular profiling

No large-scale human transcriptomic, proteomic, or single-cell datasets specific to BMFS4 patient tissue were identified in this search; the transcriptomic/epigenomic evidence base is almost entirely derived from Mysm1-knockout mouse hematopoietic tissue (RNA-seq of RP-gene programs, ChIP-based chromatin studies at Id2 and Pax5 loci). This is a knowledge gap — no GEO/ArrayExpress series specific to human BMFS4 patient bone marrow was located.

7. Anatomical Structures Affected

Organ level (primary): - Bone marrow (UBERON:0002371) — primary site of pathology (hypocellularity, dysplasia). - Immune system — spleen/lymphoid tissue (secondary, via B/NK lymphopenia), thymus (T-cell development largely spared per most reports, distinguishing from combined immunodeficiencies).

Organ level (secondary/syndromic): - Skeletal system — long bones (rhizomelic humeral shortening), hands (brachydactyly/short metacarpals), skull (trigonocephaly), craniofacial skeleton (midface hypoplasia). - Eye — lens (cataracts, UBERON:0000965). - Ear — cochlea/inner ear (sensorineural hearing loss). - Skin — epidermis (dry skin/eczema). - Central nervous system — cerebral cortex/cerebrum (reduced cerebral volume, developmental delay). - Cardiovascular system — heart (congestive heart failure reported in some patients). - Oral cavity — gingiva/teeth (gingival hyperplasia, delayed dentition).

Tissue/cell level: Hematopoietic stem and progenitor cell compartment of bone marrow stroma/parenchyma; B-lymphocyte and NK-lymphocyte lineages; chondrocyte/osteoblast lineages presumed affected in skeletal dysplasia (not specifically characterized at the cell-type level in the literature reviewed).

Subcellular level: Nucleus (GO:0005634) — chromatin-bound MYSM1 performs its primary deubiquitinase function at histone H2A within nucleosomes; a cytosolic pool (GO:0005829) mediates the innate-immune TRAF3/TRAF6/RIP2 deubiquitination function.

Localization/laterality: Systemic/bilateral — no laterality pattern reported (as expected for a germline monogenic disease affecting a generalized stem-cell and chromatin-regulatory function).

8. Temporal Development

Onset: Congenital/neonatal-to-early-infantile. Anemia has presented as early as 1 month of age (Huang et al. 2021, PMID:33858043, case title: "a 1-month-old girl") and as late as ~15 months in other reported cases; GARD lists onset "as early as the newborn stage." A milder, later-recognized adult-onset-diagnosed phenotype has also been reported (Sakovich et al. 2024, J Clin Immunol), indicating that while the underlying defect is congenital, clinical recognition/severity is variable and can be markedly delayed.

Onset pattern: Insidious/subacute for the marrow failure (progressive rather than acute catastrophic aplasia at presentation in most cases), though initial presentation can be an acute severe anemia requiring transfusion.

Progression / disease course pattern: Notably non-monotonic in several reported patients — an initial phase of transfusion dependence can be followed by spontaneous partial hematologic recovery lasting years, before later relapse and progression to pancytopenia and ultimately clonal transformation. This "transient-then-progressive" course is unusual among IBMFS and was already flagged in the original 2013 description (title: "transient transfusion-dependent anemia..."). Documented stages, drawing on Haroon et al. 2025 (PMID:40535318): 1. Infantile-onset anemia/cytopenia (often initially misclassified, e.g., as Diamond-Blackfan anemia). 2. Chronic, often fluctuating marrow failure with progressive B-/NK-cell immunodeficiency through childhood. 3. Late-childhood-to-adolescent (reported range: transformation occurring within 9–12 years of initial presentation, at patient ages 12–19 years in the largest reported series) clonal evolution with acquisition of somatic driver mutations (TP53, CALR) and cytogenetic abnormalities (monosomy 5/7, trisomy 8). 4. Transformation to hypoplastic MDS or MDS/AML.

Remission patterns: Spontaneous partial hematologic remission is specifically documented (unusual for an IBMFS) in at least one well-described case; treatment-induced remission is achievable via allogeneic HSCT (see §12), including in patients with adverse cytogenetics post-leukemic transformation (2 of the reported transformed patients achieved remission via HSCT per Haroon et al. 2025).

Critical periods: The second decade of life (roughly ages 9–19 in reported cases) appears to be the critical window for malignant clonal transformation, arguing for close surveillance (serial marrow morphology/cytogenetics) through adolescence in known BMFS4 patients, and for considering pre-emptive HSCT before transformation occurs given the poor outcome once AML supervenes (one reported patient died of septic shock 3 months post-induction chemotherapy without transplant).

9. Inheritance and Population

Epidemiology: Extremely rare — Orphanet prevalence class "<1/1,000,000"; GARD classifies it as a rare disease. Fewer than ~25 molecularly confirmed patients have been published across all case reports as of 2025 (aggregating original cohort ["nine patients" as of 2020] plus subsequent individual/small case reports and the 2025 four-patient transformation series). No formal incidence or population-registry data exist; this is a case-report-level evidence base, not a population-surveillance-derived one.

Inheritance pattern: Autosomal recessive (AR) — confirmed in every reported pedigree; unaffected heterozygous carrier parents, affected homozygous or compound-heterozygous offspring, consistent with Mendelian AR segregation and with the population-genetic evidence (gnomAD) that heterozygous LOF is well-tolerated.

Penetrance: Appears complete for biallelic LOF genotypes, though phenotypic severity is markedly variable (see Expressivity below) — the emerging adult-diagnosed case suggests that while the molecular defect is fully penetrant, clinically apparent severe marrow failure requiring diagnosis in infancy is not obligate for every genotype.

Expressivity: Variable — ranging from the classic severe infantile pancytopenia-immunodeficiency-skeletal dysplasia triad to a milder phenotype recognized only in adulthood (Sakovich et al. 2024). Genotype-phenotype correlation across the small number of reported alleles (nonsense vs. missense vs. cryptic splice) has not been systematically established, though this would be a reasonable hypothesis to test as more cases accumulate (i.e., whether residual catalytic activity from hypomorphic missense alleles, e.g., p.H656R, correlates with milder disease).

Genetic anticipation: Not applicable/not reported — this is not a repeat-expansion disorder.

Germline mosaicism: Not specifically documented in the literature reviewed, though recurrence in siblings (Alsultan 2013 original family; Huang 2021 sibling cases) is explained by biparental heterozygous-carrier segregation rather than mosaicism per se.

Founder effects: Suggested but not formally proven — the strong overrepresentation of consanguineous Middle Eastern (particularly Saudi/Gulf Arab) and some Chinese pedigrees in the literature is consistent with either regional founder alleles or simply the ascertainment effect of consanguinity increasing homozygosity for private rare variants; population-genetic founder-haplotype analysis has not been published for any specific MYSM1 allele to date.

Consanguinity role: Central — nearly all reported pedigrees involve consanguineous parents, as expected for an ultra-rare AR disease with a gene that is not under strong heterozygous constraint (so carrier frequency is presumably very low in outbred populations, making biallelic disease essentially unseen outside consanguineous unions or compound-heterozygosity in larger reference populations).

Carrier frequency: Not established in any population database (too rare/private-variant-driven for gnomAD-based carrier-frequency estimation at the disease-allele level).

Population demographics: Reported cases cluster in Middle Eastern (Saudi Arabian — original description; other Arab nationalities in the 2025 Haroon et al. series from Saudi Arabia) and East Asian (Chinese — Huang 2021, Zhan 2021, Li 2020) populations, plausibly reflecting both true regional enrichment (consanguinity rates) and ascertainment/reporting bias from specific referral centers with active IBMFS genetic-testing programs (e.g., King Faisal Specialist Hospital, Saudi Arabia) rather than confirmed differential population prevalence. No formal geographic-distribution or sex-ratio data are available; case reports do not show an obvious sex skew (both male and female patients reported), consistent with autosomal (non-sex-linked) inheritance.

10. Diagnostics

Laboratory tests: - Complete blood count showing anemia (often macrocytic, prompting DBA consideration), neutropenia, mild thrombocytopenia. - Immunoglobulin levels (hypogammaglobulinemia) and vaccine-response titers (impaired specific antibody response). - Lymphocyte subset flow cytometry: reduced/absent B cells, reduced NK cells, generally preserved T-cell numbers (helps distinguish from combined immunodeficiencies/SCID).

Bone marrow examination: Aspirate/biopsy showing hypocellularity (reported cellularity as low as 5–20%) with dysplastic erythroid and myeloid precursors — myelodysplastic features on morphology; cytogenetics initially normal, later showing acquired clonal abnormalities (monosomy 5, monosomy 7, trisomy 8) at transformation.

Genetic testing: - Gene panel / whole-exome or whole-genome sequencing targeting MYSM1 (and, given phenotypic overlap, other IBMFS genes — Fanconi anemia panel genes, RPL/RPS ribosomal protein genes for DBA, ERCC6L2, SRP72, SAMD9/SAMD9L) is the practical diagnostic route, since the clinical picture overlaps substantially with Diamond-Blackfan anemia and other congenital bone marrow failure syndromes at presentation. - Trio exome sequencing has been used successfully to identify cryptic/splice-altering variants not obvious from genomic sequence alone (Li et al. 2020, PMID:32640305, used trio WES plus RT-PCR/cDNA sequencing to functionally confirm the synonymous splice variant). - No dedicated commercial single-gene MYSM1 panel appears to be a first-line standalone test; it is typically captured within broader IBMFS/marrow-failure gene panels.

Functional/RNA-based confirmation: RT-PCR and cDNA sequencing to confirm aberrant splicing for variants of uncertain significance at intron/exon boundaries or synonymous positions (as demonstrated for c.399G>A).

Imaging: Skeletal survey (long-bone shortening, brachydactyly), brain MRI (assessing cerebral volume/hypoplasia), echocardiography (cardiac anomalies where present).

Ophthalmologic exam: Slit-lamp exam for cataracts.

Audiology: Hearing assessment given reported sensorineural hearing loss.

Differential diagnosis: Diamond-Blackfan anemia (erythroid-predominant marrow failure — a documented source of diagnostic confusion), Fanconi anemia (chromosome breakage/DEB-MMC testing should be performed to exclude), Shwachman-Diamond syndrome, SAMD9/SAMD9L-related MIRAGE/ataxia-pancytopenia syndromes, other combined immunodeficiency-with-marrow-failure syndromes (e.g., cartilage-hair hypoplasia given skeletal + immune features), and ERCC6L2-associated bone marrow failure (which similarly predisposes to MDS/AML transformation).

Screening: No population or newborn screening program exists (disease too rare and genetically heterogeneous); cascade/carrier testing of consanguineous family members and prenatal/preimplantation genetic testing are reasonable once a familial variant is identified, per standard AR-disease genetic counseling practice, though this is not specifically documented as formalized guidance in the literature reviewed.

11. Outcome/Prognosis

Survival/mortality: No formal actuarial survival statistics (5-year/10-year survival rates) exist given the extremely small published cohort. Mortality is clearly documented in the malignant-transformation setting: in the Haroon et al. 2025 series, one of four transformed patients who did not receive transplant "passed away 3 months post induction chemotherapy due to septic shock," illustrating that transformation to AML carries a poor prognosis without transplant, particularly with adverse cytogenetics.

Disease course / complications: The dominant late complication is clonal evolution to myelodysplastic syndrome and/or acute myeloid leukemia, occurring in a substantial proportion of the (small) reported cohort within roughly a decade of initial presentation — this is the single most important prognostic determinant identified in the literature and should drive a surveillance strategy (serial cytogenetics/molecular MRD-type monitoring) analogous to that used in Fanconi anemia and other pre-leukemic IBMFS.

Recovery potential: Variable — spontaneous partial hematologic recovery is documented in at least one long-term case, but this does not appear to be curative or to eliminate transformation risk; allogeneic HSCT is the only curative modality for both the marrow failure/immunodeficiency and (when performed before transformation, or in transformed patients with achievable remission) the leukemic risk.

Prognostic factors: Presence of TP53 mutation and adverse cytogenetics (monosomy 5/7) at the time of transformation appear to be poor prognostic markers, consistent with general MDS/AML risk stratification; earlier HSCT (before transformation) is inferentially the more favorable strategy, though this has not been formally tested in a comparative study given cohort size.

Prognostic biomarkers: Serial marrow cytogenetics and targeted somatic mutation panels (TP53, CALR) for transformation surveillance are the most directly evidenced prognostic tools from the 2025 case series, though no validated biomarker panel or risk score specific to BMFS4 exists.

12. Treatment

Supportive care (mainstay for most of disease course): - Chronic red cell transfusion support for severe anemia. - Immunoglobulin replacement therapy for hypogammaglobulinemia (standard practice for B-cell/antibody deficiency, though not specifically quoted in the reviewed abstracts — inferred from the immunodeficiency phenotype and general PID management standards). - Prophylactic antibiotics for recurrent infections (explicitly noted in GARD/search summaries for the recurrent-URI pattern in early childhood). - NCIT suggestion: NCIT:C15747 (Supportive Care); NCIT:C15986 (Pharmacotherapy) for immunoglobulin/antimicrobial prophylaxis.

Curative therapy — allogeneic hematopoietic stem cell transplantation (HSCT): - HSCT is explicitly stated as curative for the underlying blood/immune disease: Bahrami et al. 2017 (PMID:28115216) report that both index siblings "underwent successful allogeneic hematopoietic stem cell transplantation with sustained hematopoietic reconstitution, establishing HSCT represents a curative therapy for patients with MYSM1 deficiency." - Reduced-intensity conditioning (RIC) with fludarabine-based regimens has been used successfully, given the documented cellular genotoxic/radiosensitivity concerns: Barhoom et al. 2021 (PMID:34302415) report an HLA-identical father donor with fludarabine-based RIC achieving "full donor chimerism" with manageable grade II acute GVHD, and at one year post-transplant, "B-cell recovery, and no blood or platelet transfusion was reported." - HSCT is not without significant risk — a 2022 case report explicitly titled "Hematopoietic cell transplantation for MYSM1 deficiency: not so much an easy task" (PMID:35902396) signals recognized transplant-related complications/challenges in this population, and in the 2025 transformation series, HSCT in transformed (MDS/AML) patients with adverse cytogenetics achieved remission in some but not all cases, with chronic GVHD affecting eyes and lungs documented in one patient who achieved full chimerism. - Given the DNA-damage/genotoxic-stress hypersensitivity of MYSM1-deficient cells (§5/§6), conditioning regimens that minimize genotoxic/radiation exposure (i.e., RIC over myeloablative, and avoidance of high-dose alkylator/radiation-based regimens where feasible) are mechanistically well-justified, though formal comparative conditioning-regimen trial data do not exist for this ultra-rare disease. - NCIT suggestion: NCIT:C15431 (Hematopoietic Stem Cell Transplantation) for treatment_term, with therapeutic_modality: CELL_THERAPY.

Management of transformed disease (MDS/AML): - Induction chemotherapy has been used but with poor outcome in at least one non-transplanted patient (death from septic shock post-induction). - HSCT after achieving remission (or as consolidation) appears to be the preferred curative strategy once transformation has occurred, per the 2025 case series, though outcomes were mixed (some remission, some chronic GVHD morbidity).

Experimental/emerging therapies: No gene therapy, targeted small-molecule, or RNA-based therapeutic specific to MYSM1 deficiency was identified in this search (no registered ClinicalTrials.gov interventional trial specific to BMFS4/MYSM1 was located); given the very small patient population, disease-specific trials are unlikely in the near term, and HSCT (with individualized conditioning) remains the standard of care described in the literature.

Treatment strategy/algorithm (synthesized from the literature, not a formal published guideline): (1) supportive transfusion/Ig-replacement/antibiotic prophylaxis at diagnosis; (2) close hematologic and cytogenetic surveillance through childhood/adolescence given the ~decade-scale transformation risk; (3) proactive consideration of allogeneic HSCT with RIC before transformation to MDS/AML, given the poor prognosis once leukemic transformation occurs; (4) induction chemotherapy plus HSCT consolidation if transformation has already occurred, recognizing generally poorer outcomes in this setting, especially with TP53-mutant/adverse-cytogenetic clones.

13. Prevention

Primary prevention: Not applicable in the classic sense (this is a fully penetrant monogenic recessive disease, not a modifiable-risk-factor disease); the only "primary prevention" avenue is reproductive — genetic counseling, carrier testing of at-risk (especially consanguineous) family members, and prenatal or preimplantation genetic testing once a familial MYSM1 variant is known, following standard AR-disease reproductive genetics practice (no disease-specific guideline document was located, but this follows general ACMG/professional-society practice for rare AR disorders identified in a family).

Secondary prevention (early detection): No population or newborn screening program exists. Early recognition of the syndromic triad (marrow failure + B-/NK-cell immunodeficiency + skeletal/craniofacial/ophthalmologic features) in an infant with unexplained anemia — particularly one initially suspected of DBA who has additional immunologic or dysmorphic features — should prompt MYSM1-inclusive genetic testing.

Tertiary prevention (preventing complications once diagnosed): - Infection prophylaxis (antibiotics, immunoglobulin replacement) to reduce morbidity from the immunodeficiency. - Structured hematologic/cytogenetic surveillance to detect clonal evolution before overt leukemic transformation, given the documented ~decade-scale transformation risk — this is the single most actionable "prevention" lever identified in the literature (early detection of clonal evolution enabling pre-emptive HSCT rather than post-transformation rescue). - Avoidance of unnecessary genotoxic/radiation exposure given documented cellular radiosensitivity.

Genetic counseling: Central to family management — informing carrier parents of 25% recurrence risk per pregnancy, offering carrier testing to at-risk relatives, and discussing reproductive options; specific society guidelines for MYSM1/BMFS4 counseling were not identified (this disease is too rare to have a dedicated guideline), so counseling follows general IBMFS/AR-disease genetic counseling practice (e.g., NSGC/ACMG frameworks).

14. Other Species / Natural Disease

Taxonomy: Mouse (Mus musculus, NCBITaxon:10090) is the principal model species; no naturally occurring veterinary/companion-animal disease analog was identified in this search (no OMIA entry located for spontaneous MYSM1-related disease in domestic species).

Gene (ortholog): Mysm1, MGI:2444584, chromosome 1 (mouse), highly conserved with human MYSM1 (the 2024 review, PMID:39684760, explicitly notes "high sequence homology between murine and human MYSM1" as the basis for translating mouse mechanistic findings to human disease).

Naturally occurring/spontaneous mouse model — "meander tail" (mea): A classical spontaneous mouse mutant, meander tail, has recently (2026 bioRxiv preprint, Hamilton et al.) been shown to carry Mysm1 mutations. This strain was long known for kinked tails and a selective cerebellar anterior-lobe malformation; the preprint reports that "Mouse meander tail (mea) mutations produce kinked tails and selective malformation of the cerebellum anterior compartment" and demonstrates both neurological and hematological phenotypes arising from Mysm1 mutation, with effects on granule-cell-precursor proportions detectable by E14.5 — this is a directly relevant natural/spontaneous (non-engineered) Mysm1-mutant model that had not previously been mechanistically linked to the gene, and is a notable 2026 addition to the model literature (novel cerebellar-phenotype angle not previously connected to human BMFS4's neurodevelopmental features). (Status: preprint, not yet peer-reviewed as of this research pass — flag accordingly.)

Comparative biology: MYSM1's chromatin-regulatory and hematopoietic roles are evolutionarily conserved at least across mammals (mouse-human concordance is the basis for essentially all current mechanistic understanding, as human primary tissue studies are limited by case scarcity). The 2024 review also notes that "Mysm1 orthologs have been independently lost across various animal and fungal species" per the meander-tail preprint's phylogenetic framing — suggesting lineage-specific dispensability of MYSM1 outside mammals, relevant context for interpreting cross-species model choice.

Zoonotic potential/transmission: Not applicable — this is a non-communicable monogenic disease.

15. Model Organisms

Mouse — constitutive/conventional knockout: - Nijnik et al. 2012 (Blood, PMID:22184403) — the original characterization: Mysm1-deficient mice show defects in bone marrow hematopoiesis, resulting in lymphopenia, anemia, and thrombocytosis (note: thrombocytosis in this early mouse report, versus thrombocytopenia in human disease — a species-phenotype divergence worth noting), impaired lymphocyte development, and depletion of erythroid cells. This paper established Mysm1 as essential for HSC-supported hematopoiesis and lymphocyte differentiation, directly motivating the subsequent human disease-gene hypothesis.

Mouse — p53 double-knockout (genetic epistasis model): - Belle et al. 2015 (Blood, PMID:25710881) — Mysm1⁻/⁻p53⁻/⁻ mice: full rescue of hematopoietic and developmental defects, establishing p53 activation as the driving mechanism. High fidelity for the p53-mediated HSC-failure mechanism specifically; does not by itself model the human skeletal/craniofacial phenotype.

Mouse — ribosomal protein gene expression model: - Belle et al. 2020 (JCI Insight, PMID:32641579) — demonstrates MYSM1's direct, p53-independent role in maintaining ribosomal protein gene expression in HSCs, with loss of this regulation triggering p53 activation and hematopoietic dysfunction; links BMFS4 mechanistically to the broader ribosomopathy disease class (relevant given clinical overlap/misdiagnosis with DBA in human patients).

Mouse — NK-cell-specific model: - Nandakumar et al. 2013 (PNAS, PMID:24062447) — Mysm1-deficient mice show severely impaired NK-cell maturation (not lineage specification/commitment), mediated through MYSM1's epigenetic control of Id2 expression via NFIL3 recruitment. Directly models the human NK-cell deficiency component of BMFS4.

Mouse — B-cell/antibody-response model: - Jiang et al. 2015 (Sci Rep, PMC4562257) — despite severe B-cell developmental defects, Mysm1-deficient mice show enhanced (not simply reduced) antibody response against both T-dependent and T-independent antigens via loss of MYSM1's normal repression of plasma-cell differentiation (through Pax5 transcriptional activation). This is an important nuance: the mouse humoral phenotype is not a simple "less antibody" model, and the direct translatability to human hypogammaglobulinemia (which is the human clinical finding) is not fully resolved — a human-model mismatch worth flagging for a dismech-style entry (mouse shows paradoxically enhanced antibody response in the periphery despite developmental B-cell loss, whereas humans present with hypogammaglobulinemia/impaired vaccine response).

Mouse — catalytically dead (deubiquitinase-dead) knock-in model: - Liang et al. 2023 (Sci Rep, PMID:36611064) — "Deubiquitinase catalytic activity of MYSM1 is essential in vivo for hematopoiesis and immune cell development" — a catalytically inactivating knock-in (rather than full null) model, allowing dissection of MYSM1's catalytic (deubiquitinase) versus scaffold/non-catalytic functions in vivo; directly relevant to interpreting the human p.H656R missense allele, which specifically disrupts the JAMM catalytic domain.

Mouse — spontaneous/natural model (see §14): - Meander tail (mea) mice (Hamilton et al., 2026 bioRxiv preprint) — a classical spontaneous Mysm1-mutant strain now linked to the gene, showing combined cerebellar developmental and hematological phenotypes; potentially valuable as a naturally arising allelic series and as a new angle on modeling the neurodevelopmental component of human BMFS4 not well captured by the earlier conventional-knockout models.

Model limitations (synthesized): - No mouse model to date is reported to recapitulate the skeletal dysplasia (rhizomelic shortening, brachydactyly, trigonocephaly) or cataract phenotype of human BMFS4 — these remain modeled, at best, indirectly (the meander-tail model's cerebellar phenotype is a partial exception for the neurodevelopmental axis, but skeletal/ocular features are an unaddressed gap). - The B-cell/antibody-response phenotype shows a qualitative species divergence (enhanced vs. impaired antibody response — see Jiang et al. above), meaning direct extrapolation of the mouse humoral-immunity mechanism to the human hypogammaglobulinemia phenotype should be treated as an inference requiring caution (a HUMAN_MODEL_MISMATCH-type flag in dismech terms) rather than a demonstrated concordance. - No iPSC-derived, organoid, or human primary-tissue functional model of MYSM1 deficiency was identified in this search — the field currently relies essentially entirely on mouse genetics plus patient EBV-transformed lymphoblastoid cell lines (used, e.g., in the original 2013/2017 reports for functional confirmation of protein loss and DNA-damage-response defects) for human cellular validation. - No CRISPR screen, DepMap, or large-scale functional-genomics dataset specific to MYSM1's role in the hematopoietic/leukemic-transformation context of BMFS4 was located (broader MYSM1-in-cancer functional-genomics work, e.g., in melanoma, exists but is outside the BMFS4 disease scope).

Summary of Key Evidence Gaps (for curation triage)

Skeletal/craniofacial/ocular mechanism is essentially uncharacterized at the molecular-target level — inferred only from MYSM1's general chromatin-regulatory role, not demonstrated via specific target-gene studies, unlike the well-worked-out hematopoietic (RP-gene/p53) and NK-cell (Id2/NFIL3) axes.
Human tissue/omics data are absent — essentially all mechanistic data are mouse-derived; human confirmation rests on phenotypic concordance and a small number of patient-lymphoblastoid-line functional assays (DNA-damage sensitivity, protein-loss confirmation).
Somatic clonal-evolution-to-leukemia mechanism is documented clinically (cytogenetics/mutations) but not mechanistically dissected — the link from chronic p53-mediated HSC stress to selection for TP53-mutant/monosomy-7 clones is inferred by analogy to other IBMFS, not directly shown in BMFS4.
Genotype-phenotype correlation (nonsense/null vs. missense/hypomorphic alleles) is not systematically established despite the growing recognition of variable expressivity (severe infantile vs. milder adult-recognized presentations).
No disease-specific clinical trial, registry, or natural-history study was identified — the evidentiary base remains individual/small-series case reports, consistent with Orphanet's ultra-rare prevalence classification.

Sources

Note on a naming ambiguity worth flagging for curation: MECOM (EVI1)-related radioulnar synostosis with amegakaryocytic thrombocytopenia 2 (RUSAT2, OMIM #616738) is a genetically and clinically distinct autosomal-dominant disorder that is sometimes discussed alongside "bone marrow failure" nomenclature in search results and general literature, but it is NOT the same entry as MONDO:0020856/OMIM #618116 (MYSM1, autosomal recessive). This report addresses only the MYSM1-associated, MONDO:0020856-mapped BMFS4; RUSAT2/MECOM should not be conflated with it in curation.

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Table (click to expand)

Outcome	Count
References checked	21
Resolved	21
Unresolved (possible confabulation)	0
Unverifiable	0
Quoted claims checked	1
Quoted claims found in source	1
Quoted claims not found in source	0
References weighed for topical relevance	21
On topic	15
Off topic	0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Table (click to expand)

Outcome	Count
Terms checked	59
Resolved	51
Unresolved (possible confabulation)	0
Obsolete	3
Unverifiable	5
Terms whose name was checked	12
Terms named correctly	7
Terms named as a different term	3
Terms whose name is worth a second look	2

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

MONDO:0020856 (7 mentions) - the report calls it "if available", "label "bone marrow failure syndrome 4", "OLS"; MONDO calls it bone marrow failure syndrome 4
HP:0002846 (1 mention) - the report calls it "Abnormal B cell count is a coarse fallback if antibody-response term unavailable"; HP calls it Abnormal B cell morphology
HP:0000518 (1 mention) - the report calls it "frequent"; HP calls it Cataract

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

GO:0035522 (obsolete monoubiquitinated histone H2A deubiquitination) (1 mention)
GO:0016578 (obsolete histone deubiquitination) (1 mention)
GO:0006977 (obsolete DNA damage response, signal transduction by p53 class mediator resulting in cell cycle arrest) (1 mention) - replaced by GO:0030330

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

HP:0010976 (1 mention) - the report calls it "Decreased circulating total B cell count"; HP calls it Decreased total B cell count
HP:0000268 (1 mention) - the report calls it "Trigonocephaly"; HP calls it Dolichocephaly, and lists "Turridolichocephaly" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

MONDO:0020856 - called "if available", "label "bone marrow failure syndrome 4", "OLS"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: OMIM, GARD, ORPHA, MGI.