FGFR1-Related Hypogonadotropic Hypogonadism (FGFR1-related CHH/KS): Comprehensive Disease Characteristics Report

Scope note. “FGFR1-related hypogonadotropic hypogonadism” is commonly used clinically to denote hypogonadotropic hypogonadism 2 with or without anosmia, i.e., congenital/idiopathic GnRH deficiency due to pathogenic FGFR1 variants spanning Kallmann syndrome (KS; with hypo/anosmia) and normosmic CHH/IHH. The evidence base below comes from aggregated cohort studies and curated diagnostic resources plus individual case reports; where cohort-level statistics are provided, they are explicitly identified.

1. Disease Information

1.1 Concise overview

FGFR1-related CHH/KS is a Mendelian developmental disorder of the reproductive neuroendocrine axis caused by impaired FGFR1-mediated signaling during development, leading to deficient GnRH neuron development and/or function. Clinically it presents as absent or incomplete puberty, low sex steroids with low/inappropriately normal LH/FSH, and infertility; in the KS subtype, it is accompanied by anosmia/hyposmia and often olfactory bulb/tract hypoplasia/aplasia. Non-reproductive anomalies (e.g., dental agenesis, cleft lip/palate, synkinesia, hearing loss, renal and skeletal anomalies) occur due to broad roles of FGFR1 in embryonic patterning. (chu2023mutationspectrumof pages 1-2, dode2003lossoffunctionmutationsin pages 1-2, chung2023theinitiationand pages 2-3)

1.2 Key identifiers (ontology and genetic)

A harmonized identifier/synonym table is provided here:

Table: This table organizes the key disease labels, MONDO identifiers, OMIM/MIM references, and common synonyms relevant to FGFR1-related hypogonadotropic hypogonadism and the Kallmann syndrome spectrum. It is useful for harmonizing database entries with the terminology used in both recent literature and disease ontologies.

MONDO IDs available from Open Targets evidence include: - Hypogonadotropic hypogonadism: MONDO_0018555 (sayed2023paneltestingfor pages 2-3) - Congenital hypogonadotropic hypogonadism: MONDO_0015770 (sayed2023paneltestingfor pages 2-3) - Hypogonadotropic hypogonadism 2 with or without anosmia (FGFR1-related): MONDO_0007844 (sayed2023paneltestingfor pages 2-3)

OMIM/MIM IDs available in retrieved primary literature include: - FGFR1 gene: OMIM 136350 (men2020genotypicandphenotypic pages 1-2, dode2003lossoffunctionmutationsin pages 1-2) - Idiopathic hypogonadotropic hypogonadism (IHH): MIM 147950 (xu2023howhumangenetic pages 1-2) - Men et al. list multiple OMIM entries for KS locus heterogeneity (e.g., 308700, 147950, 244200, 610628, 612370, 612702) (men2020genotypicandphenotypic pages 1-2).

Gaps. ICD-10/ICD-11, MeSH, and Orphanet identifiers were not present in the full-texts retrieved via the current tool runs; therefore they are not asserted here.

1.3 Synonyms and alternative names

Common labels include: - Kallmann syndrome (KS) (IHH/CHH with hypo/anosmia) (chu2023mutationspectrumof pages 1-2) - Congenital hypogonadotropic hypogonadism (CHH) (with or without anosmia) (dwyer2024classesandpredictors pages 3-4) - Idiopathic hypogonadotropic hypogonadism (IHH), including normosmic IHH (xu2023howhumangenetic pages 1-2, goncalves2015novelfgfr1mutations pages 1-2)

1.4 Evidence provenance (individual vs aggregated)

• Aggregated disease-level resources: UK NHSE/PanelApp curated gene panels and gene-disease assertions informing clinical testing pipelines (sayed2023paneltestingfor pages 2-3).
• Human cohort studies: e.g., Chinese IHH cohort genotype/phenotype analyses (men2020genotypicandphenotypic pages 1-2).
• Case reports: e.g., females with primary amenorrhea and KS due to de novo FGFR1 variants (xia2021twofemalespresenting pages 1-2).

2. Etiology

2.1 Primary causal factors

Genetic cause (primary). Pathogenic variants in FGFR1 cause autosomal dominant CHH/KS (historically “KAL2”), first established by Dodé et al. in 2003 as “Loss-of-function mutations in FGFR1 cause autosomal dominant Kallmann syndrome.” (Nature Genetics; Mar 2003; https://doi.org/10.1038/ng1122) (dode2003lossoffunctionmutationsin pages 1-2).

Mechanistic cause (developmental). FGFR1 participates in FGF signaling required for development of GnRH neurons and olfactory structures; reduced dosage/signaling disrupts these developmental processes, producing GnRH deficiency with or without anosmia. (chung2023theinitiationand pages 2-3, dode2003lossoffunctionmutationsin pages 1-2)

2.2 Risk factors

• Genetic: heterozygous FGFR1 pathogenic variants (missense/nonsense/splice/indels) and, in some families, CNVs involving chromosome 8p/FGFR1 locus; Chu et al. reported a pathogenic del(8)(p12p11.22) CNV in a KS family and a frameshift FGFR1 variant (RB&E; Mar 2023; https://doi.org/10.1186/s12958-023-01074-w) (chu2023mutationspectrumof pages 1-2).
• Oligogenicity as risk/complexity: FGFR1 variants can be part of di-/oligogenic inheritance and may interact with variants in other CHH genes; oligogenicity complicates penetrance and expressivity (goncalves2015novelfgfr1mutations pages 3-4, sayed2023paneltestingfor pages 2-3).

Environmental risk factors. No specific toxin/lifestyle triggers were identified in the retrieved FGFR1-focused texts. CHH in general can show variable penetrance and may be influenced by non-genetic factors, but FGFR1-specific gene–environment interactions were not evidenced in the provided sources. (pitteloud2010complexgeneticsin pages 9-10, vezzoli2023geneticarchitectureof pages 3-5)

2.3 Protective factors

FGFR1-specific protective factors (genetic or environmental) were not identified in the retrieved sources.

2.4 Gene–environment interactions

No FGFR1-specific G×E evidence was retrieved.

3. Phenotypes

A phenotype-to-HPO mapping table (with onset/course and frequency notes where available) is provided below:

Table: This table maps key clinical features of FGFR1-related hypogonadotropic hypogonadism/Kallmann syndrome to suggested HPO terms, with onset/course and frequency notes where available. It is designed to support knowledge-base phenotype annotation grounded in the cited evidence.

3.1 Key phenotype themes (narrative)

• Core reproductive phenotype: absent/incomplete puberty with low sex steroids and low/inappropriately normal LH/FSH (CHH/IHH). (dwyer2024classesandpredictors pages 3-4)
• Olfactory phenotype: anosmia/hyposmia; MRI may show absent/hypoplastic olfactory bulbs and tracts. Xia et al. report: “Magnetic resonance imaging showed dysplastic or absent olfactory bulbs and tracts.” (J Obstet Gynaecol Res; Aug 2021; https://doi.org/10.1111/jog.14966) (xia2021twofemalespresenting pages 1-2).
• Extra-reproductive anomalies: cleft lip/palate, dental agenesis, synkinesia, corpus callosum agenesis, hearing loss, renal and skeletal anomalies. These were described in early FGFR1 discovery work and reiterated in later cohort literature. (dode2003lossoffunctionmutationsin pages 1-2, men2020genotypicandphenotypic pages 5-8, chu2023mutationspectrumof pages 1-2)

3.2 Quantitative phenotype data (recently extracted)

• In a Chinese IHH cohort study, 44.4% of mutation-positive individuals (FGFR1/FGF8/FGF17) had extra-reproductive anomalies (including dental agenesis, hearing loss, and hand malformations) (Fertility & Sterility; Jan 2020; https://doi.org/10.1016/j.fertnstert.2019.08.069) (men2020genotypicandphenotypic pages 1-2).
• Hearing loss frequency reported in the same context: “Hearing loss occurred in 5% of IHH individuals,” and a cited cohort found 16% (7/43) of KS patients with FGFR1/FGF8 mutations had hearing loss (men2020genotypicandphenotypic pages 5-8).

4. Genetic / Molecular Information

4.1 Causal gene

• FGFR1 (fibroblast growth factor receptor 1; OMIM 136350) is the canonical causal gene for hypogonadotropic hypogonadism 2 with or without anosmia (dode2003lossoffunctionmutationsin pages 1-2).

4.2 Pathogenic variant spectrum and classification

Variant classes (germline). Across studies, pathogenic FGFR1 variants include missense, nonsense, splice-site, and small indels, and larger CNVs affecting the locus. Dodé et al. enumerated multiple heterozygous variants across receptor domains in the seminal report (dode2003lossoffunctionmutationsin pages 1-2). Chu et al. (2023) state that “>300 FGFR1 mutations (missense, nonsense, splice, rare deletions) are reported in HGMD” and report both an FGFR1 frameshift and an 8p deletion CNV (chu2023mutationspectrumof pages 1-2).

Functional consequences. - Many disease-causing variants reduce receptor function (loss-of-function/haploinsufficiency), consistent with autosomal dominant disease (dode2003lossoffunctionmutationsin pages 1-2). - Some truncating variants can remove transmembrane/intracellular domains; Men et al. describe truncating receptors “without the transmembrane and intracellular domains” and report an FGFR1 variant (p.W289X) with a “dominant negative effect by interfering with the function of wild-type receptor” (men2020genotypicandphenotypic pages 5-8).

Incomplete penetrance and variable expressivity. - Gonçalves et al. report FGFR1 mutations “inherited from an apparently normal parent,” described as “cases of incomplete penetrance,” and identify a trigenic mutation in one case supporting oligogenicity (Fertility & Sterility; Nov 2015; https://doi.org/10.1016/j.fertnstert.2015.07.1142) (goncalves2015novelfgfr1mutations pages 3-4). - Dodé et al. likewise reported unaffected carriers and variable expressivity among relatives (dode2003lossoffunctionmutationsin pages 1-2).

4.3 2023 methodological advance: FGFR1 variant interpretation using human genetic context

Xu et al. (Human Genetics; Oct 2023; https://doi.org/10.1007/s00439-023-02601-w) analyze 143 FGFR1 rare sequence variants in 175 IHH probands (95 missense; 48 protein-truncating) and show that FGFR1 missense variants are regionally enriched in functional domains. Incorporating this enrichment into ACMG/AMP evidence reclassified 37% (20/54) of FGFR1 missense VUS to pathogenic/likely pathogenic, and phenotypic enrichment among non-proband carriers supported the reclassification (xu2023howhumangenetic pages 1-2).

4.4 Modifier genes / oligogenicity

Oligogenic inheritance is documented in FGFR1-related IHH/KS families (e.g., co-occurring variants in other CHH genes), complicating classical Mendelian counseling (goncalves2015novelfgfr1mutations pages 3-4, goncalves2015novelfgfr1mutations pages 1-2). Recent clinical genetics reviews emphasize that di-/oligogenic inheritance and incomplete penetrance are key interpretive challenges in CHH (sayed2023paneltestingfor pages 2-3).

4.5 Epigenetics / chromosomal abnormalities

No FGFR1-specific epigenetic mechanism evidence was retrieved. Large structural variants affecting the FGFR1 region are relevant (e.g., 8p deletion CNV reported as pathogenic) (chu2023mutationspectrumof pages 1-2).

5. Environmental Information

No FGFR1-specific environmental contributors (toxins, lifestyle, infections) were identified in the retrieved sources. The disease is best supported as a neurodevelopmental genetic disorder with variable expressivity and penetrance (dode2003lossoffunctionmutationsin pages 1-2, sayed2023paneltestingfor pages 2-3).

6. Mechanism / Pathophysiology

6.1 Causal chain (from gene to clinical phenotype)

1. Upstream trigger: germline FGFR1 loss-of-function (or signaling impairment) (dode2003lossoffunctionmutationsin pages 1-2).
2. Developmental effect: reduced FGF8→FGFR1 signaling compromises GnRH neuron neurogenesis/progenitor survival/differentiation in the olfactory placode neurogenic niche (chung2023theinitiationand pages 2-3, chung2023theinitiationand pages 6-6).
3. Anatomical effect: impairment in olfactory placode/olfactory bulb development (explaining anosmia/hyposmia in KS) and disruption of the GnRH neuron migratory route to the hypothalamus (chung2023theinitiationand pages 2-3, dode2003lossoffunctionmutationsin pages 1-2).
4. Physiologic effect: reduced hypothalamic GnRH drive → low/inappropriately normal LH/FSH → low sex steroids (hypogonadotropic hypogonadism) (dwyer2024classesandpredictors pages 3-4).
5. Clinical outcome: absent/incomplete puberty, infertility; in KS, anosmia/hyposmia and olfactory bulb/tract hypoplasia/aplasia; plus extra-reproductive congenital anomalies due to broader FGFR1 developmental roles (chu2023mutationspectrumof pages 1-2, dode2003lossoffunctionmutationsin pages 1-2).

6.2 Pathway-level summary with ontology suggestions

A structured mechanism table with suggested GO/CL/UBERON annotations is provided:

Table: This table summarizes the multilevel pathophysiology of FGFR1-related congenital hypogonadotropic hypogonadism/Kallmann syndrome, linking molecular defects in FGF signaling to GnRH neuron development, olfactory anatomy, and clinical features. It also proposes ontology annotations useful for knowledge-base curation.

6.3 Model-organism evidence (key quantitative results)

Chung & Tsai (Frontiers in Endocrinology; Apr 2023; https://doi.org/10.3389/fendo.2023.1166132) summarize strong mouse evidence for FGF signaling upstream of GnRH neuron birth: - Homozygous Fgf8 hypomorphic mice: complete loss of GnRH neurons by E11.5 - Fgfr1 hypomorphic newborn mice: ~90% reduction in GnRH neurons - Heterozygous Fgf8 hypomorphs: ~50% loss (chung2023theinitiationand pages 2-3)

A schematic depiction of the GnRH developmental trajectory and the role of Fgf8/Fgfr1 is available in the retrieved figure (chung2023theinitiationand media 627f77bc).

7. Anatomical Structures Affected

Primary systems: neuroendocrine (hypothalamic–pituitary–gonadal axis) and olfactory system. (chung2023theinitiationand pages 2-3, dwyer2024classesandpredictors pages 3-4)

Key anatomical structures (UBERON suggestions): - Olfactory placode (origin of GnRH neurons in development) (chung2023theinitiationand pages 2-3) - Cribriform plate (migration corridor) (chung2023theinitiationand pages 2-3) - Preoptic area and hypothalamus (final GnRH neuron destinations) (chung2023theinitiationand pages 2-3) - Median eminence (GnRH neurosecretory target site) (chung2023theinitiationand pages 2-3) - Olfactory bulbs/tracts (structural substrate for anosmia; often hypoplastic/aplastic on MRI) (xia2021twofemalespresenting pages 1-2)

Secondary structures (developmental anomalies): craniofacial structures (clefting), teeth (dental agenesis), kidneys (renal anomalies), limbs/digits (skeletal malformations), auditory apparatus (hearing loss). (chu2023mutationspectrumof pages 1-2, dode2003lossoffunctionmutationsin pages 1-2, men2020genotypicandphenotypic pages 5-8)

8. Temporal Development

8.1 Typical onset

Although the developmental defect is congenital, CHH/KS is often diagnosed in adolescence when puberty fails to start or progress. (dwyer2024classesandpredictors pages 3-4)

8.2 Progression and course

• Most cases require long-term management, but a clinically important subset exhibits reversal (return of endogenous reproductive function). Reversal frequency estimates in recent sources range from ~10–15% in CHH (Dwyer 2024) to 5–20% across broader literature summaries (Vezzoli 2023) (dwyer2024classesandpredictors pages 3-4, vezzoli2023geneticarchitectureof pages 3-5).

8.3 Critical periods

The key biological “critical period” is embryonic GnRH neuron neurogenesis and early migration from the olfactory placode niche, as highlighted by the Fgf8/Fgfr1 hypomorph mouse data. (chung2023theinitiationand pages 2-3)

9. Inheritance and Population

9.1 Inheritance

• Autosomal dominant inheritance is established for FGFR1-related KS/CHH with incomplete penetrance and variable expressivity; oligogenic inheritance can occur. (dode2003lossoffunctionmutationsin pages 1-2, goncalves2015novelfgfr1mutations pages 3-4, sayed2023paneltestingfor pages 2-3)

9.2 Epidemiology

• Chu et al. (2023) report estimated KS prevalence of ~1/30,000 men and ~1/125,000 women, and state KS accounts for ~50% of IHH (chu2023mutationspectrumof pages 1-2).
• CHH is reported to be about 4× more common in males in the 2024 reversal study background. (dwyer2024classesandpredictors pages 3-4)

9.3 Variant prevalence in CHH/IHH cohorts

Men et al. (2020) report the combined prevalence of FGFR1/FGF8/FGF17 mutations of 12.4% in a Chinese IHH cohort (men2020genotypicandphenotypic pages 1-2).

10. Diagnostics

10.1 Clinical criteria and hormonal testing

Dwyer et al. (Lancet Diabetes & Endocrinology; Apr 2024; https://doi.org/10.1016/S2213-8587(24)00028-7) define CHH in males as absent/incomplete puberty with low testosterone (<6 nmol/L) and low/inappropriately normal gonadotropins; partial puberty includes mean testicular volume ≥4 cc (dwyer2024classesandpredictors pages 3-4).

10.2 Imaging

• MRI evaluation of the olfactory bulbs/tracts is a key diagnostic discriminator for KS. Xia et al. emphasize MRI findings and state MRI of olfactory bulbs/tracts contributes to diagnosis (xia2021twofemalespresenting pages 5-5).

10.3 Genetic testing strategy (2023–2024 “real-world” implementation)

• Panel-based testing: Sayed & Howard (European Journal of Human Genetics; Dec 2023; https://doi.org/10.1038/s41431-022-01261-0) describe UK NHSE Genomic Medicine Service implementation of a curated CHH panel via PanelApp and note cohort studies showing an underlying variant is found in 21–51% of CHH/KS cases (sayed2023paneltestingfor pages 2-3).
• WES/WGS: Xia et al. recommend WES as a priority in females with primary amenorrhea without secondary sex characteristics and note that WES can also indicate karyotype/chromosomal abnormalities and CNVs (xia2021twofemalespresenting pages 1-2, xia2021twofemalespresenting pages 5-5).
• CNV analysis: Chu et al. employed CNV-seq and classified an 8p deletion spanning FGFR1 as pathogenic (chu2023mutationspectrumof pages 1-2).

10.4 Differential diagnosis

In females presenting primary amenorrhea, Xia et al. highlight the need for karyotype to exclude Turner syndrome and other chromosomal etiologies (both reported patients were 46,XX) and recommend focused olfactory history plus olfactory MRI (xia2021twofemalespresenting pages 1-2).

11. Outcome / Prognosis

11.1 Fertility prognosis

In male CHH, spermatogenesis and fertility are achievable in approximately ~75% of men treated with exogenous gonadotropins (FSH + hCG) or pulsatile GnRH, according to Dwyer 2024 background synthesis (dwyer2024classesandpredictors pages 3-4).

11.2 Reversal prognosis

• Spontaneous reversal occurs in ~10–15% (Dwyer 2024) (dwyer2024classesandpredictors pages 3-4).
• Dwyer 2024 further reports genetic/clinical associations: non-reversal patients were more likely to show oligogenicity than reversal patients (58.9% vs 29.3%) and baseline testicular volume positively predicted reversal (dwyer2024classesandpredictors pages 9-11).

11.3 Morbidity and quality of life impacts

While dedicated QoL instruments were not captured in the retrieved texts, Xia et al. reported osteoporosis/high fracture risk in females at diagnosis (DXA evidence), implying clinically significant morbidity from delayed diagnosis and untreated hypogonadism (xia2021twofemalespresenting pages 1-2).

12. Treatment

A structured treatment/applications table with outcomes, risks, MAXO suggestions, and clinical trial mappings is provided:

Table: This table summarizes current treatment applications for FGFR1-related congenital hypogonadotropic hypogonadism/Kallmann syndrome and CHH more broadly, including puberty induction, fertility induction, bone/metabolic support, and reversal monitoring. It integrates quantitative outcomes, practical considerations, relevant trial examples, and suggested MAXO terms for knowledge-base annotation.

12.1 Puberty induction

• Males: testosterone replacement to induce secondary sexual characteristics (dwyer2024classesandpredictors pages 3-4).
• Females: estrogen replacement with later cyclic estrogen–progestin therapy; Xia et al. describe estradiol valerate therapy in a female KS patient (xia2021twofemalespresenting pages 2-2).

12.2 Fertility induction (real-world implementations)

• Males: exogenous gonadotropins (hCG ± FSH/hMG) or pulsatile GnRH; Men et al. report that hCG/hMG increased testicular size in treated males and note reversal in a subset of IHH cases (men2020genotypicandphenotypic pages 5-8).
• Females: pulsatile GnRH for ovulation induction.

12.3 Clinical trials (examples)

• NCT02310074 (Shanghai Jiao Tong University School of Medicine; Phase 4; study start 2010; primary completion Jun 2014): compares pulsatile GnRH pump vs gonadotropin therapy in 76 men with IHH; primary endpoint partner pregnancy by 18 months; secondary endpoints include time to first sperm and sperm-density thresholds (ClinicalTrials.gov: https://clinicaltrials.gov/study/NCT02310074) (NCT02310074 chunk 1).
• NCT01976728 (Ferring; Phase 3; start 2014-04-01; completion 2018-02-23; results posted 2021-03-03): LutrePulse (gonadorelin acetate) delivered via OmniPod for ovulation induction in women with HH; primary endpoint ovulation rate and secondary pregnancy and follicular outcomes (ClinicalTrials.gov: https://clinicaltrials.gov/study/NCT01976728) (NCT01976728 chunk 1).

12.4 Targeted/advanced therapeutics

No FGFR1 gene therapy or FGFR1-targeted molecular therapy trials for FGFR1-related CHH/KS were identified in the retrieved clinical trials set; current treatment is hormonal replacement and fertility induction.

13. Prevention

Primary prevention. Not applicable in the conventional sense for a monogenic developmental disorder.

Secondary prevention (early detection). Earlier recognition of delayed puberty/amenorrhea, structured evaluation of olfaction, and timely endocrine replacement can prevent downstream morbidity (e.g., low bone density) (xia2021twofemalespresenting pages 1-2).

Genetic counseling (tertiary/recurrence prevention). Because FGFR1-related CHH/KS is often autosomal dominant with incomplete penetrance and can be oligogenic, recurrence risk counseling is complex; modern panel testing and careful variant interpretation are emphasized as essential to counseling (sayed2023paneltestingfor pages 2-3, dode2003lossoffunctionmutationsin pages 1-2).

Suggested MAXO (prevention-related) terms: genetic counseling; carrier testing; cascade screening (supported conceptually by genetics and counseling emphasis in modern diagnostic reviews) (sayed2023paneltestingfor pages 2-3).

14. Other Species / Natural Disease

No naturally occurring veterinary disease analogs were retrieved in the provided texts. The strongest cross-species evidence is mechanistic/model-organism rather than naturally occurring disease.

15. Model Organisms

15.1 Mammalian models

Mouse hypomorphic models summarized by Chung & Tsai (2023) provide strong mechanistic evidence for FGF8/FGFR1 roles in GnRH neuron neurogenesis and survival (including ~90% GnRH neuron reduction in Fgfr1 hypomorphic newborns) (chung2023theinitiationand pages 2-3).

15.2 Invertebrate models

Dodé et al. cite C. elegans data where kal1 mis/overexpression produces an axon-branching phenotype dependent on heparan-sulfate sulfation, supporting conserved extracellular-matrix modulation relevant to the FGFR1 pathway context (dode2003lossoffunctionmutationsin pages 1-2).

15.3 Model limitations

Mouse and C. elegans models capture developmental neurobiology mechanisms but do not fully reproduce the human spectrum of incomplete penetrance, variable expressivity, oligogenic inheritance, and treatment-associated reversal.

High-priority recent developments (2023–2024) — curated summary

1. Clinical diagnostic implementation: UK NHSE Genomic Medicine Service CHH panel curated via PanelApp; molecular diagnostic yield across cohorts 21–51%; key interpretive challenges are oligogenicity and incomplete penetrance (Dec 2023) (sayed2023paneltestingfor pages 2-3).
2. Variant interpretation advance for FGFR1: regional enrichment of FGFR1 missense variants across protein domains used to strengthen ACMG/AMP evidence and reclassify 37% of FGFR1 missense VUS (Oct 2023) (xu2023howhumangenetic pages 1-2).
3. Clinical course/reversal predictors: multicenter study standardizing reversal definitions and identifying predictors (cryptorchidism negative; baseline testicular volume positive; oligogenicity associated with non-reversal), while reaffirming fertility success estimates and reversal frequency (Apr 2024) (dwyer2024classesandpredictors pages 3-4, dwyer2024classesandpredictors pages 9-11).

Key abstract quotes (for knowledge-base evidence items)

• Dodé et al. (2003): “Loss-of-function mutations in FGFR1 cause autosomal dominant Kallmann syndrome.” (dode2003lossoffunctionmutationsin pages 1-2)
• Chu et al. (2023): KS prevalence and phenotype spectrum statements; KS described as IHH subtype with anosmia/hyposmia and multiple associated anomalies (chu2023mutationspectrumof pages 1-2).
• Xia et al. (2021): “Magnetic resonance imaging showed dysplastic or absent olfactory bulbs and tracts.” and recommendation that WES “should be a priority” in primary amenorrhea without secondary sex characteristics (xia2021twofemalespresenting pages 1-2).

Data gaps and limitations of this tool-run

• ICD-10/ICD-11, MeSH, Orphanet IDs were not present in the retrieved full-text corpus for FGFR1-related CHH/KS and therefore are not provided here.
• FGFR1-specific penetrance estimates (numerical) and variant allele frequencies in gnomAD were not retrievable with the current evidence set.
• FGFR1-specific genotype–treatment response statistics are limited; most treatment outcomes are reported at CHH syndrome level rather than gene-stratified.

References

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