Submitted:
27 June 2025
Posted:
30 June 2025
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Abstract
Keywords:
1. Introduction
2. Materials and Methods
- Study Design
- Preliminary Phase: Physician Training
- Study Population
- Deep Phenotyping
- Stages of Deep Phenotyping:
- 1.
- Clinical Examination and History Taking: Each patient underwent a detailed physical and neurological examination, assessing both central and peripheral nervous systems. History taking focused on identifying neurological and somatic symptoms, their onset, progression, and dynamics.
- 2.
- HPO-Based Coding of Clinical Features: Identified clinical manifestations were converted into standardized terms using the HPO system. Each symptom, its severity, and specificity were recorded using appropriate HPO codes. Special attention was paid to the correct term hierarchy: parent terms define general clinical categories, while child terms specify particular manifestations within those categories. For example, if a patient had seizures, the parent term “Seizure” (HP:0001250) was used. If generalized seizures were present, the child term “Generalized clonic seizure” (HP:0011169) provided further detail. Similarly, “Severe muscular hypotonia” was recorded as HP:0006829.
- 3.
- Phenotypic Profile Formation: Based on the coded HPO terms, an individual phenotypic profile was created for each patient. This profile served as an integrated clinical map, reflecting all detected symptoms and their characteristics. For instance, if a patient presented with generalized clonic seizures and severe muscular hypotonia, their profile would include: HP:0011169, and HP:0006829. This coding ensured a standardized and precise clinical description, which is critical for subsequent genetic interpretation.
- 4.
- Phenotype Verification: At this stage, the phenotypic profiles were analyzed to eliminate redundant or non-informative data. Each phenotypic feature was assessed for clinical relevance and consistency with known disease patterns. Results were discussed during interdisciplinary case reviews. All verified data were uploaded to the 3billion laboratory portal to maintain accuracy and support the precise interpretation of genetic findings.
- Molecular Genetic Analysis
- Reverse Phenotyping
- Evaluation of the Reduction in Diagnostic Odyssey
- Duration of the Diagnostic Process - the time interval from the onset of the first symptoms to the patient’s inclusion in the study, as well as from the time of inclusion to the final diagnosis, was examined. This allowed the evaluation of whether the new diagnostic algorithm accelerated the diagnostic process.
- Diagnostic Burden - the total number of diagnostic tests (e.g., specialist consultations, MRI, biopsies, etc.) conducted before and after the patient’s inclusion in the study was analyzed. This parameter enabled the assessment of whether the new diagnostic intervention reduced the number of additional investigations or, conversely, required more.
- Statistical Analysis
3. Results
- Results of Deep Phenotyping
- Reverse Phenotyping
- Evaluation of the Reduction in Diagnostic Odyssey
4. Discussion
- Limitations and Future Directions
5. Conclusions
6. Patents
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Abbreviations
| ACMG | American College of Medical Genetics and Genomics |
| CAT-RPND | Central Asia and Transcaucasia Rare Pediatric Neurological Diseases Genomic Consortium |
| GMFCS | Gross Motor Function Classification System |
| CNV | Copy Number Variations |
| DEE | Developmental and epileptic encephalopathy |
| ES | Exome Sequencing |
| GS | Genome Sequencing |
| HPO | Human Phenotype Ontology |
| NGS | Next-Generation Sequencing |
| NORD | National Organisation for Rare Disorders |
| RPND | Rare Paediatric Neurological Diseases |
| SDG | Sustainable Development Goals |
| SNV | Single Nucleotide Variants |
| VUS | Variant of uncertain significance |
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| Case | Age (y) | Sex | GMFS | ID | Epilepsy | HPO Terms Count | Diagnostic Odyssey Before Research (months) |
Total diagnostic procedures before participation | Total diagnostic procedures during the study | Diagnosis time (months) in the study | Clinical diagnosis refinement via reverse phenotyping | Genetic Diagnosis |
| 1 | 9 | Male | I | Severe | Yes | 13 | 106 | 7 | 2 | 5 | Yes | RAI1 |
| 2 | 7 | Female | II | Moderate | Yes | 9 | 84 | 20 | 2 | 5 | Yes | KCNQ2 |
| 3 | 10 | Male | I | Moderate | Yes | 13 | 108 | 21 | 2 | 5 | Yes | KDM6B |
| 4 | 7 months | Female | V | Severe | Yes | 10 | 7 | 7 | 2 | 5 | NA | |
| 5 | 9 | Female | II | Profound | Yes | 9 | 108 | 15 | 2 | 5 | NA | |
| 6 | 3 | Female | V | Severe | Yes | 11 | 30 | 14 | 2 | 5 | Yes | SCN8A |
| 7 | 5 | Female | II | Severe | Yes | 10 | 60 | 10 | 2 | 5 | NA | |
| 8 | 10 | Female | II | Severe | Yes | 23 | 114 | 25 | 2 | 5 | Yes | CDKL5 |
| 9 | 14 | Female | I | Moderate | Yes | 9 | 159 | 18 | 2 | 5 | Yes | UBAP2L |
| 10 | 17 | Male | I | Severe | Yes | 10 | 140 | 20 | 2 | 5 | Yes | deletion 3q29 |
| 11 | 4 | Male | II | Severe | Yes | 9 | 48 | 12 | 2 | 5 | NA | |
| 12 | 3 | Male | II | Moderate | Yes | 9 | 33 | 25 | 2 | 5 | Yes | SCN1A |
| 13 | 14 | Male | V | Severe | Yes | 10 | 168 | 14 | 2 | 5 | NA | |
| 14 | 12 | Male | I | No | No | 7 | 126 | 18 | 2 | 5 | NA | |
| 15 | 10 | Female | V | Severe | No | 10 | 120 | 26 | 2 | 5 | NA | |
| 16 | 5 | Female | II | Severe | Yes | 16 | 59 | 30 | 2 | 5 | Yes | TSC2 |
| 17 | 4 | Female | V | Profound | Yes | 10 | 48 | 30 | 2 | 5 | NA | |
| 18 | 13 | Male | II | Moderate | Yes | 13 | 156 | 28 | 2 | 5 | No | 9p24.3p22.2 |
| 19 | 16 | Male | V | Severe | Yes | 10 | 192 | 19 | 2 | 5 | NA | |
| 20 | 10 | Male | IV | Severe | Yes | 5 | 120 | 25 | 2 | 5 | Yes | FAR1 |
| 21 | 5 | Male | I | легкая | Yes | 10 | 40 | 26 | 2 | 5 | Yes | TSC1 |
| 22 | 4 | Male | V | Severe | No | 4 | 48 | 25 | 2 | 5 | NA | |
| 23 | 17 | Female | III | Mild | Yes | 10 | 204 | 32 | 2 | 5 | NA | |
| 24 | 17 | Male | V | Severe | Yes | 10 | 204 | 27 | 2 | 5 | NA | |
| 25 | 4 | Male | V | Severe | Yes | 14 | 38 | 20 | 2 | 5 | No | ANO3 |
| 26 | 3 | Female | V | Severe | No | 10 | 36 | 26 | 2 | 5 | Yes | BRAT1 |
| 27 | 5 | Male | II | Moderate | Yes | 13 | 60 | 16 | 2 | 5 | Yes | KLHL20 |
| 28 | 17 | Female | I | No | Yes | 7 | 72 | 28 | 2 | 5 | Yes | TSC2 |
| 29 | 2 | Female | V | Severe | Yes | 11 | 24 | 12 | 2 | 5 | NA | |
| 30 | 14 | Male | III | Severe | Yes | 18 | 168 | 20 | 2 | 5 | No | SCN1A |
| 31 | 3 | Male | V | Severe | Yes | 11 | 36 | 20 | 2 | 5 | NA | |
| 32 | 4 | Male | V | Severe | Yes | 12 | 48 | 20 | 2 | 5 | NA | |
| 33 | 14 | Male | II | Moderate | No | 10 | 168 | 23 | 2 | 5 | NA | |
| 34 | 1 | Male | V | Severe | No | 14 | 12 | 15 | 2 | 5 | NA | |
| 35 | 4 | Female | II | Severe | Yes | 7 | 48 | 15 | 2 | 5 | Yes | deletion 17q12. |
| 36 | 5 | Male | V | Severe | No | 9 | 60 | 14 | 2 | 5 | Yes | PRICKLE2 |
| 37 | 6 | Female | V | Severe | No | 11 | 72 | 32 | 2 | 5 | Yes | SLC17A5 |
| 38 | 14 | Female | II | Mild | No | 9 | 168 | 39 | 2 | 5 | Yes | MTHFS |
| 39 | 6 | Female | II | Severe | Yes | 9 | 72 | 15 | 2 | 5 | Yes | KCND2 |
| 40 | 3 | Male | V | Severe | No | 20 | 36 | 20 | 2 | 5 | NA | |
| 41 | 7 | Female | V | Severe | Yes | 9 | 84 | 40 | 2 | 5 | Yes | FRA10AC1 |
| 42 | 3 | Male | V | Severe | Yes | 15 | 36 | 20 | 2 | 5 | NA | |
| 43 | 4 | Male | V | Profound | Yes | 8 | 48 | 19 | 2 | 5 | NA | |
| 44 | 13 | Male | IV | Moderate | Yes | 12 | 156 | 29 | 2 | 5 | NA | |
| 45 | 3 | Male | V | Severe | No | 9 | 36 | 20 | 2 | 5 | NA | |
| 46 | 12 | Male | II | Moderate | No | 15 | 144 | 28 | 2 | 5 | Yes | LAMA1 |
| 47 | 6 | Female | V | Severe | Yes | 18 | 72 | 20 | 2 | 5 | Yes | TRIO |
| 48 | 4 | Male | II | Severe | Yes | 14 | 48 | 15 | 2 | 5 | NA | |
| 49 | 5 | Male | V | Severe | Yes | 30 | 60 | 20 | 2 | 5 | Yes | CUL4B, GRIK2 |
| 50 | 4 | Female | I | Severe | Yes | 15 | 48 | 15 | 2 | 5 | Yes | DYRK1A |
| 51 | 7 | Male | II | Severe | Yes | 10 | 84 | 20 | 2 | 5 | NA | |
| 52 | 10 | Male | II | Severe | No | 20 | 120 | 38 | 2 | 5 | Yes | VPS13B |
| 53 | 3 | Female | IV | Severe | Yes | 19 | 36 | 20 | 2 | 5 | Yes | ARID1B |
| 54 | 3 | Male | V | Severe | No | 16 | 36 | 18 | 2 | 5 | NA | |
| 55 | 4 | Male | V | Severe | Yes | 5 | 48 | 20 | 2 | 5 | NA | |
| 56 | 16 | Male | I | Mild | No | 2 | 90 | 14 | 2 | 5 | NA | |
| 57 | 7 | Female | II | Severe | Yes | 12 | 84 | 25 | 2 | 5 | Yes | duplication 9p24.3p21.2 |
| 58 | 17 | Male | V | Severe | Yes | 11 | 204 | 20 | 2 | 5 | NA | |
| 59 | 4 | Male | III | Severe | Yes | 12 | 48 | 18 | 2 | 5 | NA | |
| 60 | 13 | Male | II | Severe | No | 10 | 156 | 28 | 2 | 4 | Yes | ITPR1 |
| 61 | 15 | Female | II | Moderate | Yes | 5 | 180 | 38 | 2 | 4 | Yes | L2HGDH |
| 62 | 4 | Male | V | Severe | No | 13 | 48 | 45 | 2 | 4 | Yes | OCRL |
| 63 | 1 | Female | V | Severe | No | 24 | 12 | 18 | 2 | 4 | Yes | HRAS |
| 64 | 3 | Male | V | Severe | No | 14 | 36 | 20 | 2 | 4 | NA | |
| 65 | 5 | Male | II | Severe | No | 18 | 60 | 30 | 2 | 4 | Yes | IDS, MKKS |
| 66 | 5 | Male | V | Severe | Yes | 8 | 60 | 20 | 2 | 4 | Yes | MTTL1 |
| 67 | 5 | Male | V | Severe | No | 19 | 60 | 15 | 2 | 4 | NA | |
| 68 | 6 | Male | IV | Severe | Yes | 20 | 72 | 18 | 2 | 4 | NA | |
| 69 | 8 | Male | II | Moderate | Yes | 23 | 96 | 25 | 2 | 4 | Yes | FGFR2 |
| 70 | 7 | Female | II | Severe | Yes | 17 | 84 | 14 | 2 | 4 | Yes | KMT2D |
| 71 | 10 | Male | V | Severe | Yes | 13 | 120 | 20 | 2 | 4 | NA | |
| 72 | 5 | Male | II | Severe | No | 18 | 60 | 28 | 2 | 3 | Yes | deletion 5p15.33p14.3 |
| 73 | 3 | Male | IV | Severe | No | 11 | 36 | 15 | 2 | 3 | NA | |
| 74 | 14 | Male | I | Mild | No | 6 | 168 | 10 | 2 | 3 | NA | |
| 75 | 8 | Female | II | Severe | Yes | 23 | 96 | 25 | 2 | 3 | NA | |
| 76 | 6 | Female | II | Severe | No | 22 | 72 | 20 | 2 | 3 | Yes | ARID1B |
| 77 | 4 | Male | II | Severe | No | 15 | 48 | 18 | 2 | 3 | NA | |
| 78 | 6 | Male | II | Severe | Yes | 17 | 72 | 20 | 2 | 3 | NA | |
| 79 | 11 | Female | IV | Severe | Yes | 13 | 132 | 20 | 2 | 3 | Yes | WDFY3 |
| 80 | 12 | Male | I | Severe | Yes | 7 | 72 | 18 | 2 | 3 | Yes | GRIN2A |
| 81 | 6 months | Male | V | Profound | Yes | 18 | 6 | 12 | 2 | 3 | Yes | WWOX |
| Case | Gene | Zygosity | Phenotype | ACMG criteria |
| 1 | RAI1 | Heterozygous | Smith-Magenis syndrome | Pathogenic |
| 2 | KCNQ2 | Heterozygous | Developmental and epileptic encephalopathy 7 | Likely pathogenic |
| 6 | SCN8A | Heterozygous | Developmental and epileptic encephalopathy 13 | VUS |
| 8 | CDKL5 | Heterozygous | ‘Developmental and epileptic encephalopathy 2 | Likely pathogenic |
| 12 | SCN1A | Heterozygous | Dravet syndrome | Likely pathogenic |
| 3 | KDM6B | Heterozygous | Neurodevelopmental disorder with coarse facies and mild distal skeletal abnormalities | Likely pathogenic |
| 9 | UBAP2L | Heterozygous | Neurodevelopmental disorder with impaired language, behavioral abnormalities, and dysmorphic facies | Likely pathogenic |
| 16 | TSC2 | Heterozygous | Tuberous sclerosis-2 | Pathogenic |
| 20 | FAR1 | Heterozygous | Cataracts, spastic paraparesis, and speech delay | Pathogenic |
| 21 | TSC1 | Heterozygous | Tuberous sclerosis-1 | Pathogenic |
| 27 | KLHL20 | Heterozygous | KLHL20-related disorder | Likely pathogenic |
| 25 | ANO3 | Heterozygous | Dystonia 24 | Pathogenic |
| 26 | BRAT1 | Heterozygous | Neurodevelopmental disorder with cerebellar atrophy and with or without seizures | Likely pathogenic |
| 28 | TSC2 | Heterozygous | Tuberous sclerosis-2 | VUS |
| 30 | SCN1A | Heterozygous | SCN1A-related disorder | VUS |
| 36 | PRICKLE2 | Heterozygous | PRICKLE2-related neurodevelopmental disorder | VUS |
| 37 | SLC17A5 | Homozygous | Salla disease | Pathogenic |
| 38 | MTHFS | Heterozygous | Neurodevelopmental disorder with microcephaly, epilepsy, and hypomyelination | Likely pathogenic |
| 39 | KCND2 | Heterozygous | KCND2-related neurodevelopmental disorder | Likely pathogenic |
| 41 | FRA10AC1 | Homozygous | Neurodevelopmental disorder with growth retardation, dysmorphic facies, and corpus callosum abnormalities | Pathogenic |
| 46 | LAMA1 | Heterozygous | Poretti-Boltshauser syndrome | Likely pathogenic |
| 47 | TRIO | Heterozygous | Intellectual developmental disorder, autosomal dominant 44, with microcephaly | VUS |
| 49 | CUL4B | Hemizygous | Intellectual developmental disorder, X-linked syndromic, Cabezas type | VUS |
| 50 | DYRK1A | Heterozygous | Intellectual developmental disorder, autosomal dominant 7 | Pathogenic |
| 53 | ARID1B | Heterozygous | Coffin-Siris syndrome 1 | Likely pathogenic |
| 52 | VPS13B | Heterozygous | Cohen syndrome | Pathogenic |
| 60 | ITPR1 | Heterozygous | Gillespie syndrome | VUS |
| 61 | L2HGDH | Homozygous | L2-hydroxyglutaric aciduria | Pathogenic |
| 62 | OCRL | Hemizygous | Lowe syndrome | VUS |
| 63 | HRAS | Heterozygous | Costello syndrome | Pathogenic |
| 65 | MKKS | Homozygous | BARDET-BIEDL SYNDROME 6 | Pathogenic |
| IDS | Hemizygous | Mucopolysaccharidosis II | Pathogenic | |
| 66 | MTTL1 | Heteroplasmic | Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes | Pathogenic |
| 69 | FGFR2 | Heterozygous | Crouzon syndrome | Pathogenic |
| 70 | KMT2D | Heterozygous | Kabuki syndrome 1 | Pathogenic |
| 76 | ARID1B | Heterozygous | Coffin-Siris syndrome 1 | Pathogenic |
| 79 | WDFY3 | Heterozygous | Microcephaly 18, primary, autosomal dominant | VUS |
| 80 | GRIN2A | Heterozygous | Epilepsy, focal, with speech disorder and with or without impaired intellectual development | Pathogenic |
| 81 |
WWOX | Homozygous | Developmental and epileptic encephalopathy 28 | Likely pathogenic |
| Case | CNV | Phenotype |
| 10 | deletion 3q29 | Chromosome 3q29 microdeletion syndrome |
| 18 | duplication 9p24.3p22.2 | N/A |
| 35 | deletion 17q12. | Chromosome 17q12 deletion syndrome |
| 57 | duplication 9p24.3p21.2 | Trisomy 9p |
| 72 | deletion 5p15.33p14.3 | Cri-du-chat syndrome |
| Indicator | Before Study Participation | After Genetic Investigation |
| Mean diagnostic duration (months) | 102.6 | 4.2 |
| Standard deviation (months) | 57.2 | 0.77 |
| Median diagnostic duration (months) | 72 | 5 |
| Range (months) | 6 – 204 | 3 – 5 |
| Number of diagnostic procedures (median) | 20 [7–45] | 2 [2–2] |
| Number of confirmed genetic diagnoses | 0 (pre-genetic stage) | 43 out of 81 (53%) |
| Proportion of variants of uncertain significance | – | 3 out of 43 (7% of identified variants) |
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