Identification of a novel partial deletion of STS associated with pre-Descemet corneal dystrophy and X-linked ichthyosis.

Purpose: Pre-Descemet corneal dystrophy (PDCD) with X-linked ichthyosis (XLI) is associated with mutations in or deletions of the steroid sulfatase gene (STS). As only three cases of genetically confirmed PDCD associated with XLI have been reported, we sought to expand our understanding of the genetic basis of PDCD by screening STS in two previously unreported families. Materials and Methods: The affected individuals underwent cutaneous and slit-lamp examinations. Saliva samples collected from each affected individual served as a source of DNA for the amplification of the 10 coding exons of STS and flanking DNA markers. Results: The slit-lamp examination of three affected men (two of whom were brothers) from two families revealed bilateral punctate posterior corneal stromal opacities anterior to the Descemet membrane. Cutaneous examination demonstrated dry, coarse, scaly ichthyotic changes characteristic of XLI in all individuals. Genetic examination of the STS locus on the X chromosome in Case 1 revealed a deletion that spanned across DNA markers DXS1130-DXS237, which includes all the coding exons (exons 1-10) of STS. Genetic screening of Cases 2 and 3 revealed a partial deletion of the STS locus involving exons 1-7 and flanking DNA marker DXS1130 on the X chromosome. Conclusions: PDCD with XLI may be associated with either partial or complete deletion of STS. Despite the identification of point mutations, partial deletion, and complete deletion of STS in different affected families reported to date, there was no apparent difference in the affected phenotype between the families, suggesting that the identified variants likely all resulted in loss of function of steroid sulfatase.

Genetic Heterogeneity of X-Linked Ichthyosis in the Republic of North Ossetia-Alania, Case Series Report.

North Caucasus has always been a residence of a lot of different authentic ethnic groups speaking different languages and still living their traditional lifestyle. The diversity appeared to be reflected in the accumulation of different mutations causing common inherited disorders. X-linked ichthyosis represents the second most common form of genodermatoses after ichthyosis vulgaris. Eight patients from three unrelated families of different ethnic origin, Kumyk, Turkish Meskhetians, and Ossetian, with X-linked ichthyosis from the North Caucasian Republic of North Ossetia-Alania were examined. NGS technology was implied for searching for disease-causing variants in one of the index patients. Known pathogenic hemizygous deletion in the short arm of chromosome X encompassing the STS gene was defined in the Kumyk family. A further analysis allowed us to establish that likely the same deletion was a cause of ichthyosis in a family belonging to the Turkish Meskhetians ethnic group. In the Ossetian family, a likely pathogenic nucleotide substitution in the STS gene was defined; it segregated with the disease in the family. We molecularly confirmed XLI in eight patients from three examined families. Though in two families, Kumyk and Turkish Meskhetian, we revealed similar hemizygous deletions in the short arm of chromosome X, but their common origin was not likely. Forensic STR markers of the alleles carrying the deletion were defined to be different. However, here, common alleles haplotype is hard to track for a high local recombination rate. We supposed the deletion could arise as a de novo event in a recombination hot spot in the described and in other populations with a recurrent character. Defined here are the different molecular genetic causes of X-linked ichthyosis in families of different ethnic origins sharing the same residence place in the Republic of North Ossetia-Alania which could point to the existing reproductive barriers even inside close neighborhoods.

Medical and neurobehavioural phenotypes in male and female carriers of Xp22.31 duplications in the UK Biobank.

Deletions spanning the STS (steroid sulfatase) gene at Xp22.31 are associated with X-linked ichthyosis, corneal opacities, testicular maldescent, cardiac arrhythmia, and higher rates of developmental and mood disorders/traits, possibly related to the smaller volume of some basal ganglia structures. The consequences of duplication of the same genomic region have not been systematically assessed in large or adult samples, although evidence from case reports/series has indicated high rates of developmental phenotypes. We compared multiple measures of physical and mental health, cognition and neuroanatomy in male (n = 414) and female (n = 938) carriers of 0.8-2.5 Mb duplications spanning STS, and non-carrier male (n = 192, 826) and female (n = 227, 235) controls from the UK Biobank (recruited aged 40-69 from the UK general population). Clinical and self-reported diagnoses indicated a higher prevalence of inguinal hernia and mania/bipolar disorder respectively in male duplication carriers, and a higher prevalence of gastro-oesophageal reflux disease and blistering/desquamating skin disorder respectively in female duplication carriers; duplication carriers also exhibited reductions in several depression-related measures, and greater happiness. Cognitive function and academic achievement did not differ between comparison groups. Neuroanatomical analysis suggested greater lateral ventricle and putamen volume in duplication carriers. In conclusion, Xp22.31 duplications appear largely benign, but could slightly increase the likelihood of specific phenotypes (although results were only nominally-significant). In contrast to deletions, duplications might protect against depressive symptoms, possibly via higher STS expression/activity (resulting in elevated endogenous free steroid levels), and through contributing towards an enlarged putamen volume. These results should enable better genetic counselling of individuals with Xp22.31 microduplications.

Mood symptoms, neurodevelopmental traits, and their contributory factors in X-linked ichthyosis, ichthyosis vulgaris and psoriasis.

BACKGROUND: High rates of adverse mood/neurodevelopmental traits are seen in multiple dermatological conditions, and can significantly affect patient quality of life. Understanding the sex-specific nature, magnitude, impact and basis of such traits in lesser-studied conditions like ichthyosis, is important for developing effective interventions. AIM: To quantify and compare relevant psychological traits in men with X-linked ichthyosis (XLI, n = 54) or in XLI carrier women (n = 83) and in patients with ichthyosis vulgaris (IV, men n = 23, women n = 59) or psoriasis (men n = 30, women n = 122), and to identify factors self-reported to contribute most towards depressive, anxious and irritable phenotypes. METHODS: Participants recruited via relevant charities or social media completed an online survey of established questionnaires. Data were analysed by sex and skin condition, and compared with general population data. RESULTS: Compared with the general population, there was a higher rate of lifetime prevalence of mood disorder diagnoses across all groups and of neurodevelopmental disorder diagnoses in the XLI groups. The groups exhibited similarly significant elevations in recent mood symptoms (Cohen d statistic 0.95-1.28, P < 0.001) and neurodevelopmental traits (d = 0.31-0.91, P < 0.05) compared with general population controls, and self-reported moderate effects on quality of life and stigmatization. There were strong positive associations between neurodevelopmental traits and recent mood symptoms (r > 0.47, P < 0.01), and between feelings of stigmatization and quality of life, particularly in men. Numerous factors were identified as contributing significantly to mood symptoms in a condition or sex-specific, or condition or sex-independent, manner. CONCLUSION: We found that individuals with XLI, IV or psoriasis show higher levels of mood disorder diagnoses and symptoms than matched general population controls, and that the prevalence and severity of these is similar across conditions. We also identified a number of factors potentially conferring either general or condition-specific risk of adverse mood symptoms in the three skin conditions, which could be targeted clinically and/or through education programmes. In clinical practice, recognizing mood/neurodevelopmental problems in ichthyosis and psoriasis, and addressing the predisposing factors identified by this study should benefit the mental health of affected individuals.

Medical and neurobehavioural phenotypes in carriers of X-linked ichthyosis-associated genetic deletions in the UK Biobank.

BACKGROUND: X-linked ichthyosis (XLI) is an uncommon dermatological condition resulting from a deficiency of the enzyme steroid sulfatase (STS), often caused by X-linked deletions spanning STS. Some medical comorbidities have been identified in XLI cases, but small samples of relatively young patients has limited this. STS is highly expressed in subcortical brain structures, and males with XLI and female deletion carriers appear at increased risk of developmental/mood disorders and associated traits; the neurocognitive basis of these findings has not been examined. METHODS: Using the UK Biobank resource, comprising participants aged 40-69 years recruited from the general UK population, we compared multiple medical/neurobehavioural phenotypes in males (n=86) and females (n=312) carrying genetic deletions spanning STS (0.8-2.5 Mb) (cases) to male (n=190 577) and female (n=227 862) non-carrier controls. RESULTS: We identified an elevated rate of atrial fibrillation/flutter in male deletion carriers (10.5% vs 2.7% in male controls, Benjamini-Hochberg corrected p=0.009), and increased rates of mental distress (p=0.003), irritability (p<0.001) and depressive-anxiety traits (p<0.05) in male deletion carriers relative to male controls completing the Mental Health Questionnaire. While academic attainment was unaffected, male and female deletion carriers exhibited impaired performance on the Fluid Intelligence Test (Cohen's d≤0.05, corrected p<0.1). Neuroanatomical analysis in female deletion carriers indicated reduced right putamen and left nucleus accumbens volumes (Cohen's d≤0.26, corrected p<0.1). CONCLUSION: Adult males with XLI disease-causing deletions are apparently at increased risk of cardiac arrhythmias and self-reported mood problems; altered basal ganglia structure may underlie altered function and XLI-associated psychiatric/behavioural phenotypes. These results provide information for genetic counselling of deletion-carrying individuals and reinforce the need for multidisciplinary medical care.

A novel nonsense mutation in the STS gene in a Pakistani family with X-linked recessive ichthyosis: including a very rare case of two homozygous female patients.

BACKGROUND: X-linked ichthyosis (XLI; OMIM# 308100) is a recessive keratinization disorder characterized by the presence of dark brown, polygonal, adherent scales on different parts of the body surface. It almost exclusively affects males and the estimated prevalence ranges from 1:2000-6000 in males worldwide. Extracutaneous manifestations are frequent including corneal opacities, cryptorchidism, neuropsychiatric symptoms or others. Up to 90% of XLI cases are caused by recurrent hemizygous microdeletion encompassing entire STS gene on chromosome Xp22.3, while only a minority of patients shows partial deletions or loss of function point mutations in STS. Larger deletions also involving contiguous genes are identified in syndromic patients. METHODS: Here, we report clinical and genetic findings of a large Pakistani family having 16 affected individuals including 2 females with XLI. Molecular karyotyping and direct DNA sequencing of coding region of the STS gene was performed. RESULTS: The clinical manifestations in affected individuals involved generalized dryness and scaling of the skin with polygonal, dark scales of the skin on scalp, trunk, limbs, and neck while sparing face, palms and soles. There were no associated extra-cutaneous features such as short stature, cryptorchidism, photophobia, corneal opacities, male baldness, and behavioral, cognitive, or neurological phenotypes including intellectual disability, autism or attention deficit hyperactivity disorder. Molecular karyotyping was normal and no copy number variation was found. Sanger sequencing identified a novel hemizygous nonsense mutation (c.287G > A; p.W96*), in exon 4 of STS gene in all affected male individuals. In addition, two XLI affected females in the family were found to be homozygous for the identified variant. CONCLUSIONS: This study is useful for understanding the genetic basis of XLI in the patients studied, for extending the known mutational spectrum of STS, diagnosis of female carriers and for further application of mutation screening in the genetic counseling of this family.

Genetics of Inherited Ichthyoses and Related Diseases.

Inherited ichthyoses are classified as Mendelian disorders of cornification (MEDOC), which are defined on the basis of clinical and genetic features and are mainly divided into non-syndromic and syndromic ichthyoses. Numerous genes, which encode for corresponding proteins, are involved in the normal differentiation of keratinocytes (cornification) and participate in the formation of a functional epidermal barrier. To date, mutations in more than 50 genes are known to result in various types of ichthyoses. Thanks to modern genetic diagnostic methods based on targeted next generation sequencing (NGS), approximately 80-90% of cases can be resolved at present. Further sequencing methods covering the whole exome (WES) or whole genome (WGS) will obviously elucidate another portion of the remaining unknown ichthyoses in the future.

X-linked ichthyosis: Molecular findings in four pedigrees with inconspicuous clinical manifestations.

BACKGROUND: X-linked ichthyosis (XLI) is the second most common type of ichthyosis, which is characterized by wide and symmetric distribution of adherent, dry, and polygonal scales on the skin. Steroid sulfatase (STS) gene, which is located at chromosome Xp22.31, has been identified as the pathogenic gene of XLI. METHODS: In this study, chromosome karyotype analysis, bacterial artificial chromosomes-on-Beads™ (BoBs) assay, fluorescence in situ hybridization (FISH), and single nucleotide polymorphism array (SNP-array) were employed for the prenatal diagnoses in three pregnant women with high-risk serological screening results and a pregnant woman with mental retardation. RESULTS: STS deletion was identified at chromosome Xp22.31 in all four fetuses. Postnatal follow-up confirmed the diagnosis of ichthyosis in two male fetuses and revealed normal dermatological manifestations in other two female fetuses carrying ichthyosis. CONCLUSION: The results of the present study demonstrate that a combination of karyotypying, prenatal BoBs, FISH, and SNP-array may avoid the missed detection of common microdeletions and ensure the accuracy of the detection results, which provides a feasible tool for the reliable etiological diagnosis and better genetic counseling of XLI.

Long and very long lamellar phases in model stratum corneum lipid membranes.

Membrane models of the stratum corneum (SC) lipid barrier, either healthy or affected by recessive X-linked ichthyosis, constructed from ceramide [Cer; nonhydroxyacyl sphingosine N-tetracosanoyl-d-erythro-sphingosine (CerNS24) alone or with omega-O-acylceramide N-(32-linoleyloxy)dotriacontanoyl-d-erythro-sphingosine (CerEOS)], FFAs(C16-24), cholesterol (Chol), and sodium cholesteryl sulfate (CholS) were investigated. X-ray diffraction (XRD) revealed a previously unreported polymorphism of the membranes. In the absence of CerEOS, the membranes formed a short lamellar phase (SLP; the repeat distance d = 5.3 nm), a medium lamellar phase (MLP; d = 10.6 nm), or very long lamellar phases (VLLP; d = 15.9 and 21.2 nm). An increased CholS-to-Chol ratio modulated the membrane polymorphism, although the CholS phase separated at ≥ 7 weight% (of total lipids). The presence of CerEOS led to the stable long lamellar phase (LLP) with d = 12.2 nm and prevented VLLP formation. Our XRD results agree well with recently published cryo-electron microscopy data for vitreous skin sections, while also revealing new structures. Thus, lamellar phases with long repeat distances (MLP and VLLP) may be formed in the absence of omega-O-acylceramide, whereas these ultralong Cer species likely stabilize the final SC lipid architecture of LLP by riveting the adjacent lipid layers.

X-linked ichthyosis: Clinical and molecular findings in 35 Italian patients.

Recessive X-linked ichthyosis (XLI), the second most common ichthyosis, is caused by mutations in the STS gene encoding the steroid sulfatase enzyme. A complete deletion of the STS gene is found in 85%-90% of cases. Rarely, larger deletions involving contiguous genes are detected in syndromic patients. We report the clinical and molecular genetic findings in a series of 35 consecutive Italian male patients. All patients underwent molecular testing by MLPA or aCGH, followed, in case of negative results, by next-generation sequencing analysis. Neuropsychiatric, ophthalmological and paediatric evaluations were also performed. Our survey showed a frequent presence of disease manifestations at birth (42.8%). Fold and palmoplantar surfaces were involved in 18 (51%) and 7 (20%) patients, respectively. Fourteen patients (42%) presented neuropsychiatric symptoms, including attention-deficit hyperactivity disorder and motor disabilities. In addition, two patients with mental retardation were shown to be affected by a contiguous gene syndrome. Twenty-seven patients had a complete STS deletion, one a partial deletion and 7 carried missense mutations, two of which previously unreported. In addition, a de novo STS deletion was identified in a sporadic case. The frequent presence of palmoplantar and fold involvement in XLI should be taken into account when considering the differential diagnosis with ichthyosis vulgaris. Our findings also underline the relevance of involving the neuropsychiatrist in the multidisciplinary management of XLI. Finally, we report for the first time a de novo mutation which shows that STS deletion can also occur in oogenesis.

Evidence of the high prevalence of neurological disorders in nonsyndromic X-linked recessive ichthyosis: a retrospective case series.

BACKGROUND: X-linked recessive ichthyosis (XLI) is a relatively common type of ichthyosis caused by a deficiency in the steroid sulfatase (STS) enzyme. It is the only type of ichthyosis that can be both syndromic and nonsyndromic. Typical clinical features include dark-brown scale of variable size favouring the extensor surfaces of the extremities. OBJECTIVES: To characterize clinically nonsyndromic XLI, with a particular focus on extracutaneous manifestations. METHODS: This was a multicentre retrospective review of clinical findings from a case series of patients with a clinical and genetic diagnosis of XLI. RESULTS: We identified 30 patients with XLI belonging to 25 different families carrying a deletion in the STS locus. All patients had dark scales of variable size on the extensor surfaces of the extremities. Lack of flexural involvement and pruritus were common but inconsistent findings, whereas palmoplantar hyperlinearity was absent in all but one patient. A history of orchiopexy was present in 10% and thus was more common than expected vs. the general population (3%). Neurological disorders including epilepsy (13%) and attention deficit hyperactivity disorder (ADHD; 30%) were over-represented in patients with XLI. CONCLUSIONS: This was a retrospective study with a limited number of patients. In the absence of confirmatory genetic testing and family history of the disease, dark-brown scale of the extensor surfaces and the absence of palmoplantar hyperlinearity appear to be the most reliable clinical findings supporting a diagnosis of XLI. Dermatologists should be aware of the high prevalence of ADHD and epilepsy in patients with nonsyndromic XLI.

The Belgian MicroArray Prenatal (BEMAPRE) database: A systematic nationwide repository of fetal genomic aberrations.

OBJECTIVE: With the replacement of karyotyping by chromosomal microarray (CMA) in invasive prenatal diagnosis, new challenges have arisen. By building a national database, we standardize the classification and reporting of prenatally detected copy number variants (CNVs) across Belgian genetic centers. This database, which will link genetic and ultrasound findings with postnatal development, forms a unique resource to investigate the pathogenicity of variants of uncertain significance and to refine the phenotypic spectrum of pathogenic and susceptibility CNVs. METHODS: The Belgian MicroArray Prenatal (BEMAPRE) consortium is a collaboration of all genetic centers in Belgium. We collected data from all invasive prenatal procedures performed between May 2013 and July 2016. RESULTS: In this three-year period, 13 266 prenatal CMAs were performed. By national agreement, a limited number of susceptibility CNVs and no variants of uncertain significance were reported. Added values for using CMA versus conventional karyotyping were 1.8% in the general invasive population and 2.7% in cases with an ultrasound anomaly. Of the reported CNVs, 31.5% would have remained undetected with non-invasive prenatal test as the first-tier test. CONCLUSION: The establishment of a national database for prenatal CNV data allows for a uniform reporting policy and the investigation of the prenatal and postnatal genotype-phenotype correlation.

CO-OCCURRENCE OF PRIMARY MICROCEPHALY CAUSED BY A NOVEL HOMOZYGOUS ASPM MUTATION ALONG WITH X-LINKED ICHTHYOSIS IN THE SAME PATIENT.

Autosomal recessive primary microcephaly is a heterogeneous genetic disorder caused by genes that affect neurogenesis. This form of microcephaly has not been associated with other congenital anomalies. ASPM mutations have been identified as the major cause implicated in autosomal recessive primary microcephaly. X-linked recessive ichthyosis, is an inborn error of steroid sulfatase metabolism characterized by dark and adhesive scaly skin. Here, we examined an Egyptian boy presenting with microcephaly and simplified gyral pattern. Additionally, he had ichthyosis that goes with the X-linked type. Mutation analyses of the ASPM gene for autosomal recessive primary microcephaly and STS gene of X-linked recessive ichthyosis were conducted revealing a co-occurrence of a novel homozygous splice site mutation of ASPM gene (c.2936+1G>A) and a partial deletion of STS spanning from exon 7-10. We propose that the phenotype of our patient results from the combined effects of mutations in both ASPM and STS that account for the neurological signs and skin manifestations, respectively. The association of isolated X-linked recessive ichthyosis and autosomal recessive primary microcephaly has never been reported in the literature. Careful clinical and genetic assessment of patients with atypical clinical phenotypes is crucial for detecting such rare double mutations and thus proper genetic counseling.

[Genetic analysis of a rare case with Kallman syndrome and steroid sulfatase deficiency].

OBJECTIVE: To explore the pathogenesis of a patient featuring azoospermia and steroid sulfatase deficiency. METHODS: Polymerase chain reaction (PCR), G-banded karyotyping and Illumina Human CytoSNP-12 Beadchip analysis were conducted. RESULTS: STS sites PCR showed that there was no deletion in the AZF zone. G-banding analysis indicated an unknown structural change in chromosome X, which was verified by single nucleotide polymorphism array (SNP array) as a 5.4 Mb deletion in Xp22.31-p22.33. CONCLUSION: The Xp22.31-p22.33 deletion probably underlies the Kallman syndrome and steroid sulfatase defect in the patient.

[Identification of gene mutation and prenatal diagnosis in a family with X-linked ichthyosis].

X-linked ichthyosis (XLI) is a metabolic disease with steroid sulfatase deficiency and often occurs at birth or shortly after birth. The encoding gene of steroid sulfatase, STS, is located on the short arm of the X chromosome, and STS deletion or mutation can lead to the development of this disease. This study collected the data on the clinical phenotype from a family, and the proband, a boy aged 11 years with full-term vaginal delivery, had dry and rough skin and black-brown scaly patches, mainly in the abdomen and extensor aspect of extremities. Peripheral blood samples were collected from each family member and DNA was extracted. Multiplex ligation-dependent probe amplification (MLPA) was used to measure the copy number of STS on the X chromosome. Whole-genome microarray was used to determine the size of the segment with microdeletion in the X chromosome. MLPA was then used for prenatal diagnosis for the mother of the proband. The results revealed that the proband and another two male patients had hemizygotes in STS deletion. Gene microarray identified a rare deletion with a size of 1.6 Mb at Xp22.31 (chrX: 6,516,735-8,131,442). Two female family members were found to be carriers. Prenatal diagnosis showed that the fetus carried by the proband's mother was a carrier of this microdeletion. This study showed STS gene deletion in this family of XLI, which causes the unique skin lesions of XLI. MLPA is a convenient and reliable technique for the molecular and prenatal diagnosis of XLI.

Role of cholesterol sulfate in epidermal structure and function: lessons from X-linked ichthyosis.

X-linked ichthyosis is a relatively common syndromic form of ichthyosis most often due to deletions in the gene encoding the microsomal enzyme, steroid sulfatase, located on the short area of the X chromosome. Syndromic features are mild or unapparent unless contiguous genes are affected. In normal epidermis, cholesterol sulfate is generated by cholesterol sulfotransferase (SULT2B1b), but desulfated in the outer epidermis, together forming a 'cholesterol sulfate cycle' that potently regulates epidermal differentiation, barrier function and desquamation. In XLI, cholesterol sulfate levels my exceed 10% of total lipid mass (≈1% of total weight). Multiple cellular and biochemical processes contribute to the pathogenesis of the barrier abnormality and scaling phenotype in XLI. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.

The phenotype spectrum of X-linked ichthyosis identified by chromosomal microarray.

BACKGROUND: Steroid sulfatase (STS) gene disruption causes X-linked ichthyosis (XLI). Interrogating the entire genome through chromosomal microarray (CMA), a test primarily used to screen patients with noncutaneous congenital anomalies, may detect STS deletions incidentally. OBJECTIVE: We sought to determine the variability of skin features associated with STS deletions diagnosed through CMA and to compare these findings with XLI cases reported in the literature and recognized in a dermatology clinic. METHODS: Male patients with an STS deletion were identified from 23,172 consecutive postnatal blood samples tested with CMA at Mayo Clinic. A comparison group of male patients with biochemically confirmed XLI was ascertained in the dermatology clinic. The available patient medical records, skin histopathology, and photographs were evaluated and a literature search of patients with XLI was conducted. RESULTS: Children whose diagnosis was made incidentally through CMA had milder skin phenotypes, including dryness or eczema, or both, and did not manifest the polygonal or "dirty" scale described as typical of XLI in the literature. LIMITATIONS: The small sample size, limited clinical information, and assessment by nondermatologists in a subset of cases may have influenced the results. CONCLUSION: STS deletions may cause a milder skin phenotype than the typical presentation of XLI.

Novel homozygous deletion of segmental KAL1 and entire STS cause Kallmann syndrome and X-linked ichthyosis in a Chinese family.

Kallmann syndrome (KS) is a genetically heterogeneous disease characterised by hypogonadotrophic hypogonadism in association with anosmia or hyposmia. This condition affects 1 in 10 000 men and 1 in 50,000 women. Defects in seventeen genes including KAL1 gene contribute to the molecular basis of KS. We report the clinical characteristics, molecular causes and treatment outcome of two Chinese brothers with KS and X-linked ichthyosis. The phenotypes of the patients were characterised by bilateral cryptorchidism, unilateral renal agenesis in one patient but normal kidney development in another. The patients had low serum testosterone, follicle-stimulating hormone and luteinising hormone levels and a blunt response to the gonadotrophin-releasing hormone stimulation test. After human chorionic gonadotrophin treatment, the serum testosterone levels were normalized, and the pubic hair, penis length and testicular volumes were greatly improved in both of the patients. The two affected siblings had the same novel deletion at Xp22.3 including exons 9-14 of KAL1 gene and entire STS gene. Our study broadens the mutation spectrum in the KAL1 gene associated with KS and facilitates the genetic diagnosis and counselling for KS.