Responsiveness to a physiological regimen of GnRH therapy and relation to genotype in women with isolated hypogonadotropic hypogonadism

Physiological and Pharmacological overview of the Gonadotropin Releasing Hormone

Gonadotropin-releasing Hormone (GnRH) is a decapeptide responsible for the control of the reproductive functions. It shows C- and N-terminal aminoacid modifications and two other distinct isoforms have been so far identified. The biological effects of GnRH are mediated by binding to high-affinity G-protein couple receptors (GnRHR), showing characteristic very short C tail. In mammals, including humans, GnRH-producing neurons originate in the embryonic nasal compartment and during early embryogenesis they undergo rapid migration towards the hypothalamus; the increasing knowledge of such mechanisms improved diagnostic and therapeutic approaches to infertility. The pharmacological use of GnRH, or its synthetic peptide and non-peptide agonists or antagonists, provides a valid tool for reproductive disorders and assisted reproduction technology (ART). The presence of GnRHR in several organs and tissues indicates additional functions of the peptide. The identification of a GnRH/GnRHR system in the human endometrium, ovary, and prostate has extended the functions of the peptide to the physiology and tumor transformation of such tissues. Likely, the activity of a GnRH/GnRHR system at the level of the hippocampus, as well as its decreased expression in mice brain aging, raised interest in its possible involvement in neurogenesis and neuronal functions. In conclusion, GnRH/GnRHR appears to be a fascinating biological system that exerts several possibly integrated pleiotropic actions in the complex control of reproductive functions, tumor growth, neurogenesis, and neuroprotection. This review aims to provide an overview of the physiology of GnRH and the pharmacological applications of its synthetic analogs in the management of reproductive and non-reproductive diseases.

[Molecular genetics and phenotypic features of congenital isolated hypogonadotropic hypogonadism]

Congenital isolated hypogonadotropic hypogonadism includes a group of diseases related to the defects of secretion and action of gonadotropin-releasing hormone (GNRH) and gonadotropins. In a half of cases congenital hypogonadism is associated with an impaired sense of smell. It's named Kallmann syndrome. Now 40 genes are known to be associated with function of hypothalamus pituitary gland and gonads. Phenotypic features of hypogonadism and therapy effectiveness are related to different molecular defects. However clinical signs may vary even within the same family with the same molecular genetic defect. Genotype phenotype correlation in patients with congenital malformations prioritizes the search for mutations in candidate genes. There are data of significant contribution of oligogenicity into the phenotype of the disease are presented in the review. Moreover, an issue of current isolated hypogonadotropic hypogonadism definition and classification revision is raised in the review due to hypogonadotropic hypogonadism development while there are mutations in genes not associated with GNRH neurons secretion and function.

Gonadotropin-releasing hormone analogs: Mechanisms of action and clinical applications in female reproduction

Extra-hypothalamic GnRH and extra-pituitary GnRH receptors exist in multiple human reproductive tissues, including the ovary, endometrium and myometrium. Recently, new analogs (agonists and antagonists) and modes of GnRH have been developed for clinical application during controlled ovarian hyperstimulation for assisted reproductive technology (ART). Additionally, the analogs and upstream regulators of GnRH suppress gonadotropin secretion and regulate the functions of the reproductive axis. GnRH signaling is primarily involved in the direct control of female reproduction. The cellular mechanisms and action of the GnRH/GnRH receptor system have been clinically applied for the treatment of reproductive disorders and have widely been introduced in ART. New GnRH analogs, such as long-acting GnRH analogs and oral nonpeptide GnRH antagonists, are being continuously developed for clinical application. The identification of the upstream regulators of GnRH, such as kisspeptin and neurokinin B, provides promising potential to develop these upstream regulator-related analogs to control the hypothalamus-pituitary-ovarian axis.

Predictive factors for pituitary response to pulsatile GnRH therapy in patients with congenital hypogonadotropic hypogonadism

Pulsatile gonadotropin-releasing hormone (GnRH) may induce spermatogenesis in most patients with congenital hypogonadotropic hypogonadism (CHH) by stimulating gonadotropin production, while the predictors for a pituitary response to pulsatile GnRH therapy were rarely investigated. Therefore, the aim of our study is to investigate predictors of the pituitary response to pulsatile GnRH therapy. This retrospective cohort study included 82 CHH patients who received subcutaneous pulsatile GnRH therapy for at least 1 month. Patients were categorized into poor or normal luteinizing hormone (LH) response subgroups according to their LH level (LH <2 IU l⁻¹ or LH ≥2 IU l⁻¹) 1 month into pulsatile GnRH therapy. Gonadotropin and testosterone levels, testicular size, and sperm count were compared between the two subgroups before and after GnRH therapy. Among all patients, LH increased from 0.4 ± 0.5 IU l⁻¹ to 7.5 ± 4.4 IU l⁻¹ and follicle-stimulating hormone (FSH) increased from 1.1 ± 0.9 IU l⁻¹ to 8.8 ± 5.3 IU l⁻¹. A Cox regression analysis showed that basal testosterone level (β = 0.252, P = 0.029) and triptorelin-stimulated FSH_60min (β = 0.518, P = 0.01) were two favorable predictors for pituitary response to GnRH therapy. Nine patients (9/82, 11.0%) with low LH response to GnRH therapy were classified into the poor LH response subgroup. After pulsatile GnRH therapy, total serum testosterone level was 39 ± 28 ng dl⁻¹ versus 248 ± 158 ng dl⁻¹ (P = 0.001), and testicular size was 4.0 ± 3.1 ml versus 7.9 ± 4.5 ml (P = 0.005) in the poor and normal LH response subgroups, respectively. It is concluded that higher levels of triptorelin-stimulated FSH_60minand basal total serum testosterone are favorable predictors of pituitary LH response to GnRH therapy.

Similarities and differences in the reproductive phenotypes of women with congenital hypogonadotrophic hypogonadism caused by GNRHR mutations and women with polycystic ovary syndrome

STUDY QUESTION

Does the phenotype of women with normosmic congenital hypogonadotrophic hypogonadism (nCHH) and pituitary resistance to GnRH caused by biallelic mutations in the GnRH receptor (GNRHR) (nCHH/bi-GNRHR) differ from that of women with polycystic ovary syndrome (PCOS)?

SUMMARY ANSWER

Women with nCHH/bi-GNRHR have variable pubertal development but nearly all have primary amenorrhea and an exaggerated LH response to GnRH stimulation, similar to that seen in women with PCOS.

WHAT IS KNOWN ALREADY

Women with nCHH/bi-GNRHR are very rare and their phenotype at diagnosis is not always adequately documented. The results of gonadotrophin stimulation by acute GnRH challenge test and ovarian features have not been directly compared between these patients and women with PCOS.

STUDY DESIGN, SIZE, DURATION

We describe the phenotypic spectrum at nCHH/bi-GNRHR diagnosis in a series of 12 women. Their reproductive characteristics and acute responses to GnRH were compared to those of 70 women with PCOS.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients and controls (healthy female volunteers aged over 18 years) were enrolled in a single French referral centre. Evaluation included clinical and hormonal studies, pelvic ultrasonography and GnRH challenge test. We also functionally characterized two missense GNRHR mutations found in two new consanguineous families.

MAIN RESULTS AND THE ROLE OF CHANCE

Breast development was highly variable at nCHH/bi-GNRHR diagnosis, but only one patient had undeveloped breasts. Primary amenorrhea was present in all but two cases. In untreated nCHH/bi-GNRHR patients, uterine height (UH) correlated (P = 0.01) with the circulating estradiol level and was shorter than in 23 nulliparous post-pubertal age-matched controls (P < 0.0001) and than in 15 teenagers with PCOS under 20-years-old (P < 0.0001) in which PCOS was revealed by primary amenorrhea or primary-secondary amenorrhea. Unexpectedly, the stimulated LH peak response in nCHH/bi-GNRHR patients was variable, and often normal or exaggerated. Interestingly, the LH peak response was similar to that seen in the PCOS patients, but the latter women had significantly larger mean ovarian volume (P < 0.001) and uterine length (P < 0.001) and higher mean estradiol (P < 0.001), anti-Müllerian hormone (AMH) (P = 0.02) and inhibin-B (P < 0.001) levels. In the two new consaguineous families, the affected nCHH/bi-GNRHR women carried the T269M or Y290F GNRHR missense mutation in the homozygous state. In vitro analysis of GnRHR showed complete or partial loss-of-function of the T269M and Y290F mutants compared to their wildtype counterpart.

LIMITATIONS, REASONS FOR CAUTION

The number of nCHH/bi-GNRHR patients reported here is small. As this disorder is very rare, an international study would be necessary to recruit a larger cohort and consolidate the phenotypic spectrum observed here.

WIDER IMPLICATIONS OF THE FINDINGS

In teenagers and young women with primary amenorrhea, significant breast and uterine development does not rule out CHH caused by biallelic GNRHR mutations. In rare patients with PCOS presenting with primary amenorrhea and a mild phenotype, the similar exaggerated pituitary LH responses to GnRH in PCOS and nCHH/bi-GNRHR patients could lead to diagnostic errors. This challenge test should therefore not be recommended. As indicated by consensus and guidelines, careful analysis of clinical presentation and measurements of testosterone circulating levels remain the basis of PCOS diagnosis. Also, analysis of ovarian volume, UH and of inhibin-B, AMH, estradiol and androgen circulating levels could help to distinguish between mild PCOS and nCHH/bi-GNRHR.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the French National Research Agency (ANR) grant ANR-09-GENO-017 KALGENOPATH, France; and by the Italian Ministry of Education, University and Research (MIUR) grant PRIN 2012227FLF_004, Italy. The authors declare no conflict of interest.

Clinical Management of Congenital Hypogonadotropic Hypogonadism

The initiation and maintenance of reproductive capacity in humans is dependent on pulsatile secretion of the hypothalamic hormone GnRH. Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder that results from the failure of the normal episodic GnRH secretion, leading to delayed puberty and infertility. CHH can be associated with an absent sense of smell, also termed Kallmann syndrome, or with other anomalies. CHH is characterized by rich genetic heterogeneity, with mutations in >30 genes identified to date acting either alone or in combination. CHH can be challenging to diagnose, particularly in early adolescence where the clinical picture mirrors that of constitutional delay of growth and puberty. Timely diagnosis and treatment will induce puberty, leading to improved sexual, bone, metabolic, and psychological health. In most cases, patients require lifelong treatment, yet a notable portion of male patients (∼10% to 20%) exhibit a spontaneous recovery of their reproductive function. Finally, fertility can be induced with pulsatile GnRH treatment or gonadotropin regimens in most patients. In summary, this review is a comprehensive synthesis of the current literature available regarding the diagnosis, patient management, and genetic foundations of CHH relative to normal reproductive development.

Association study of the three functional polymorphisms (TAS2R46G>A, OR4C16G>A, and OR4X1A>T) with recurrent pregnancy loss

This study was purposed to investigate whether genetic polymorphisms in the function of stop-gain are associated with a fetal or placental development play roles and a development of idiopathic recurrent pregnancy loss (RPL) in Korean females. Three stop-gain polymorphisms were selected using next-generation sequencing screening, which allows for the rigorous examination and discovery of previously uncharacterized stop-gain genes and stop-gain expression profiles. Accordingly, we investigated the association of stop-gain polymorphisms in Korean women with RPL. Three functional polymorphisms in the TAS2R46G>A (rs2708381), OR4C16G>A (rs1459101), and OR4X1A>T (rs10838851) genes were genotyped using polymerase chain reaction (PCR)-restriction fragment length polymorphism assays and real-time PCR analysis. We determined that the OR4C16G>A polymorphism was associated with idiopathic RPL in Korean women (Adjusted odds ratio [AOR] 1.782; 95% confidence interval [CI] 1.004-3.163; P = 0.048, and AOR 1.766; 95% CI 1.020-3.059; P = 0.042). In addition, the prevalence of RPL was increased in women with the OR4C16GA + AA genotype and blood coagulation measures of prothrombin time (PT) > 10.4 s (AOR 8.292; 95% CI 2.744-25.054). We suggest that the OR4C16G>A polymorphism might serve as a clinically useful biomarker for the development, prevention, and prognosis of RPL.

GENETICS IN ENDOCRINOLOGY: Genetic counseling for congenital hypogonadotropic hypogonadism and Kallmann syndrome: new challenges in the era of oligogenism and next-generation sequencing

Congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome (KS) are rare, related diseases that prevent normal pubertal development and cause infertility in affected men and women. However, the infertility carries a good prognosis as increasing numbers of patients with CHH/KS are now able to have children through medically assisted procreation. These are genetic diseases that can be transmitted to patients' offspring. Importantly, patients and their families should be informed of this risk and given genetic counseling. CHH and KS are phenotypically and genetically heterogeneous diseases in which the risk of transmission largely depends on the gene(s) responsible(s). Inheritance may be classically Mendelian yet more complex; oligogenic modes of transmission have also been described. The prevalence of oligogenicity has risen dramatically since the advent of massively parallel next-generation sequencing (NGS) in which tens, hundreds or thousands of genes are sequenced at the same time. NGS is medically and economically more efficient and more rapid than traditional Sanger sequencing and is increasingly being used in medical practice. Thus, it seems plausible that oligogenic forms of CHH/KS will be increasingly identified making genetic counseling even more complex. In this context, the main challenge will be to differentiate true oligogenism from situations when several rare variants that do not have a clear phenotypic effect are identified by chance. This review aims to summarize the genetics of CHH/KS and to discuss the challenges of oligogenic transmission and also its role in incomplete penetrance and variable expressivity in a perspective of genetic counseling.

GnRH in the Human Female Reproductive Axis

Gonadotropin-releasing hormone (GnRH) is recognized as the central regulator of the functions of the pituitary-gonadal axis. The increasing knowledge on the mechanisms controlling the development and the function of GnRH-producing neurons is leading to a better diagnostic and therapeutic approach for hypogonadotropic hypogonadisms and for alterations of the puberty onset. During female life span, the function of the GnRH pulse generator may be affected by a number of inputs from other neuronal systems, offering alternative strategies for diagnostic and therapeutic interventions. Moreover, the identification of a GnRH/GnRH receptor system in both human ovary and endometrium has widened the spectrum of action of the peptide outside its hypothalamic functions. The pharmacological use of GnRH itself or its synthetic analogs (agonists and antagonists) provides a valid tool to either stimulate or block gonadotropin secretion and to modulate the female fertility in several reproductive disorders and in assisted reproduction technology. The use of GnRH agonists in young female patients undergoing chemotherapy is also considered a promising therapeutic approach to counteract iatrogenic ovarian failure.

The Use of Variant Maps to Explore Domain-Specific Mutations of FGFR1

Here we describe the genotype-phenotype correlations of diseases caused by variants in Fibroblast Growth Factor Receptor 1 ( FGFR1) and report a novel, de novo variant in FGFR1 in an individual with multiple congenital anomalies. The proband presented with bilateral cleft lip and palate, malformed auricles, and bilateral ectrodactyly of his hands and feet at birth. He was later diagnosed with diabetes insipidus, spastic quadriplegia, developmental delay, agenesis of the corpus callosum, and enlargement of the third cerebral ventricle. We noted the substantial phenotypic overlap with individuals with Hartsfield syndrome, the rare combination of holoprosencephaly and ectrodactyly. Sequencing of FGFR1 identified a previously unreported de novo variant in exon 11 (p.Gly487Cys), which we modeled to determine its predicted effect on the protein structure. Although it was not predicted to significantly alter protein folding stability, it is possible this variant leads to the formation of nonnative intra- or intermolecular disulfide bonds. We then mapped this and other disease-associated variants to a 3-dimensional model of FGFR1 to assess which protein domains harbored the highest number of pathogenic changes. We observed the greatest number of variants within the domains involved in FGF binding and FGFR activation. To further explore the contribution of each variant to disease, we recorded the phenotype resulting from each FGFR1 variant to generate a series of phenotype-specific protein maps and compared our results to benign variants appearing in control databases. It is our hope that the use of phenotypic maps such as these will further the understanding of genetic disease in general and diseases caused by variation in FGFR1 specifically.

The induction of ovulation by pulsatile administration of GnRH: an appropriate method in hypothalamic amenorrhea

The induction of ovulation by the means of a pump which assures the pulsatile administration of GnRH is a well-known method that applies to women suffering from amenorrhea of hypothalamic origin. Although a simple and efficient method to establish fertility, it is underused. Twelve patients suffering from this condition, 1 Kallmann syndrome, 4 normosmic isolated hypogonadotropic hypogonadism, and 7 functional hypothalamic amenorrhea desiring pregnancy were treated. They underwent one or more cycles of pulsatile GnRH, at a frequency of 90 minutes, either by the intravenous or the subcutaneous route. An initial dose of 5 μg per pulse in the intravenous route was administered and of 15 μg per pulse in the subcutaneous route. The treatment was monitored by regular dosing of gonadotropins, estradiol and progesterone, and the development of follicles and ovulation was monitored by intra-vaginal ultrasonography. All the patients had documented ovulation, after a mean of 17 days on pump stimulation. Single ovulation occurred in 30 of 33 treatment cycles, irrespective of the route of administration. Ovulation resulted in 10 pregnancies over 7 patients (2 pregnancies in 3 of them), distributed in the 3 diagnostic categories. For comparison, a patient with PCOS treated similarly, disclosed premature LH surge without ovulation.

Pulsatile gonadotropin-releasing hormone therapy in persistent amenorrheic weight-recovered anorexia nervosa patients

OBJECTIVE

To compare hormonal and clinical responses to GnRH pulsatile treatment in weight-recovered anorexia nervosa patients (Rec-AN) with persistent functional hypothalamic amenorrhea (HA) vs. in patients with secondary and primary HA.

DESIGN

Retrospective, observational, ambulatory study.

SETTING

University hospital.

PATIENT(S)

Forty-one women: 19 Rec-AN (body mass index >18.5 kg/m² without menses recovery), 15 secondary HA without any eating disorders patients (SHA), and 7 primary HA patients (PHA).

INTERVENTION(S)

Gonadotropin-releasing hormone pulsatile therapy.

MAIN OUTCOME MEASURE(S)

Baseline E₂, LH, and P plasma levels and their changes during induction cycles; ovulation, follicular recruitment, and pregnancies.

RESULTS

The Rec-AN group displayed higher basal E₂ and LH plasma levels after GnRH injection compared with SHA and PHA. Higher E₂ and LH levels were observed during induction cycles in Rec-AN compared with SHA and PHA. Follicular recruitment was higher in Rec-AN. The ovulation rate was higher in Rec-AN compared with PHA but similar to SHA.

CONCLUSION(S)

This study showed increased gonadal status and higher E₂ response to pulsatile GnRH therapy in persistent amenorrheic weight-recovered AN compared with HA from other causes. It suggests that their individual set-point of body weight allowing a fully functional gonadal axis is not reached yet. Specific factors of gonadal inertia in Rec-AN still remain unclear.

Fertility Issues for Patients with Hypogonadotropic Causes of Delayed Puberty

Delayed puberty presenting with low gonadotropins has multiple causes. Self-limited delay (constitutional delay) is generally considered benign, but adult height and bone mineral density may be compromised, and fertility has not been studied. Functional hypogonadotropic hypogonadism due to a stressor is thought to resolve with removal of the stressor, but reproductive endocrine dysfunction can sometimes persist. Most but not all patients with idiopathic hypogonadotropic hypogonadism, a typically long-lasting condition, can achieve fertility with exogenous hormone therapy. Future studies are needed to determine fertility outcomes in self-limited delayed puberty and to more clearly define prognostic factors for fertility in functional and idiopathic hypogonadotropic hypogonadism.

Expert consensus document: European Consensus Statement on congenital hypogonadotropic hypogonadism--pathogenesis, diagnosis and treatment

Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder caused by the deficient production, secretion or action of gonadotropin-releasing hormone (GnRH), which is the master hormone regulating the reproductive axis. CHH is clinically and genetically heterogeneous, with >25 different causal genes identified to date. Clinically, the disorder is characterized by an absence of puberty and infertility. The association of CHH with a defective sense of smell (anosmia or hyposmia), which is found in ∼50% of patients with CHH is termed Kallmann syndrome and results from incomplete embryonic migration of GnRH-synthesizing neurons. CHH can be challenging to diagnose, particularly when attempting to differentiate it from constitutional delay of puberty. A timely diagnosis and treatment to induce puberty can be beneficial for sexual, bone and metabolic health, and might help minimize some of the psychological effects of CHH. In most cases, fertility can be induced using specialized treatment regimens and several predictors of outcome have been identified. Patients typically require lifelong treatment, yet ∼10-20% of patients exhibit a spontaneous recovery of reproductive function. This Consensus Statement summarizes approaches for the diagnosis and treatment of CHH and discusses important unanswered questions in the field.

[Congenital hypogonadotropic hypogonadism and Kallmann syndrome in males]

Congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome (KS) are a group of rare disorders responsible for complete or partial pubertal failure due to lack or insufficient secretion of the pituitary gonadotropins LH and FSH. The underlying neuroendocrine abnormalities are classically divided into two main groups: molecular defects of the gonadotrope cascade leading to isolated normosmic CHH (nCHH), and developmental abnormalities affecting the hypothalamic location of GnRH neurons, but also olfactory bulbs and tracts morphogenesis and responsible for KS. Identification of genetic abnormalities related to CHH/KS has provided major insights into the pathways critical for the development, maturation and function of the gonadotrope axis. In patients affected by nCHH, particularly in familial cases, genetic alterations affecting GnRH secretion (mutations in GNRH1, GPR54/KISS1R and TAC3 and TACR3) or the GnRH sensitivity of gonadotropic cells (GNRHR) have been found. Mutations in KAL1, FGFR1/FGF8/FGF17, PROK2/PROKR2, NELF, CHD7, HS6ST1, WDR11, SEMA3A, SOX10, IL17RD2, DUSP6, SPRY4, and FLRT3 have been associated with KS but sometimes also with its milder hyposmic/normosmic CHH clinical variant. A number of observations, particularly in sporadic cases, suggest that CHH/KS is not always a monogenic mendelian disease as previously thought but rather a digenic or potentially oligogenic condition. Before the age of 18 years, the main differential diagnosis of isolated nCHH is the relatively frequent constitutional delay of growth and puberty (CDGP). However, in male patients with pubertal delay and low gonadotropin levels, the presence of micropenis and/or cryptorchidism argues strongly in favor of CHH and against CDGP. CHH/KS are not always congenital life-long disorders as initially thought, because in nearly 10 % of patients the disease seems not permanent, as evidenced by partial recovery of the pulsatile activity of the hypothalamic-pituitary-gonadal axis after discontinuation of treatment in adulthood (the so-called reversible CHH/KS). The clinical and hormonal diagnosis and the therapeutic management as well as the genetic counseling of these patients will be discussed here based on the experience acquired in our department during the past 30 years, from monitoring more than 400 patients with these rare conditions.

Profiling, Bioinformatic, and Functional Data on the Developing Olfactory/GnRH System Reveal Cellular and Molecular Pathways Essential for This Process and Potentially Relevant for the Kallmann Syndrome

During embryonic development, immature neurons in the olfactory epithelium (OE) extend axons through the nasal mesenchyme, to contact projection neurons in the olfactory bulb. Axon navigation is accompanied by migration of the GnRH+ neurons, which enter the anterior forebrain and home in the septo-hypothalamic area. This process can be interrupted at various points and lead to the onset of the Kallmann syndrome (KS), a disorder characterized by anosmia and central hypogonadotropic hypogonadism. Several genes has been identified in human and mice that cause KS or a KS-like phenotype. In mice a set of transcription factors appears to be required for olfactory connectivity and GnRH neuron migration; thus we explored the transcriptional network underlying this developmental process by profiling the OE and the adjacent mesenchyme at three embryonic ages. We also profiled the OE from embryos null for Dlx5, a homeogene that causes a KS-like phenotype when deleted. We identified 20 interesting genes belonging to the following categories: (1) transmembrane adhesion/receptor, (2) axon-glia interaction, (3) scaffold/adapter for signaling, (4) synaptic proteins. We tested some of them in zebrafish embryos: the depletion of five (of six) Dlx5 targets affected axonal extension and targeting, while three (of three) affected GnRH neuron position and neurite organization. Thus, we confirmed the importance of cell-cell and cell-matrix interactions and identified new molecules needed for olfactory connection and GnRH neuron migration. Using available and newly generated data, we predicted/prioritized putative KS-disease genes, by building conserved co-expression networks with all known disease genes in human and mouse. The results show the overall validity of approaches based on high-throughput data and predictive bioinformatics to identify genes potentially relevant for the molecular pathogenesis of KS. A number of candidate will be discussed, that should be tested in future mutation screens.