A rare and preventable aetiology of neurodevelopmental delay and epilepsy: familial glucocorticoid deficiency.

OBJECTIVES: Familial glucocorticoid deficiency (FGD) is a rare autosomal recessive disorder characterised by isolated glucocorticoid deficiency. Melanocortin receptor 2 (MC2R) mediates the functions of adrenocorticotropic hormone (ACTH) in the adrenal cortex. MC2R accessory protein (MRAP) is a transmembrane protein involved in the trafficking of MC2R to the cell surface. Mutations in MC2R and MRAP genes cause FGD type 1 and 2. In the present case series, we evaluate the clinical characteristics and long-term follow-up of six cases with FGD due to mutations in MC2R and MRAP. CASE PRESENTATION: Data of six cases with FGD (five with mutations in MC2R and one with a mutation in MRAP) who were being followed at our paediatric endocrine centre was evaluated. Diagnosis of FGD was considered in case of elevated ACTH and inappropriately low cortisol level, and exclusion of other aetiologies. The main presenting complaints were hyperpigmentation and hypoglycaemic convulsion in all cases. During a follow-up period of 26-115 months, one patient with homozygous 560delT mutation in MC2R, one female with G226R mutation in MC2R and one female with IVS3ds+1delG mutation in MRAP had a neurodevelopmental delay (NDD), while the other three patients had normal neurodevelopment. CONCLUSIONS: FGD patients due to MC2R and MRAP mutations with early diagnosis and compliance to the hydrocortisone therapy had normal neurodevelopment, while delay in diagnosis and poor compliance was associated with severe hypoglycaemic convulsions and subsequent complications NDD.

Emerging roles of melanocortin receptor accessory proteins (MRAP and MRAP2) in physiology and pathophysiology.

Melanocortin-2 receptor accessory protein (MRAP) has an unusual dual topology and influences the expression, localisation, signalling and internalisation of the melanocortin receptor 2 (MC2); the adrenocorticotropic hormone (ACTH) receptor. Mutations in MRAP are associated with familial glucocorticoid deficiency type-2 and evidence is emerging of the importance of MRAP in adrenal development and ACTH signalling. Human MRAP has two functional splice variants: MRAP-α and MRAP-ß, unlike MRAP-ß, MRAP-α has little expression in brain but is highly expressed in ovary. MRAP2, identified through whole human genome sequence analysis, has approximately 40% sequence homology to MRAP. MRAP2 facilitates MC2 localisation to the cell surface but not ACTH signalling. MRAP and MRAP2 have been found to regulate the surface expression and signalling of all melanocortin receptors (MC1-5). Additionally, MRAP2 moderates the signalling of the G-protein coupled receptors (GCPRs): orexin, prokineticin and GHSR1a; the ghrelin receptor. Whilst MRAP appears to be mainly involved in glucocorticoid synthesis, an important role is emerging for MRAP2 in regulating appetite and energy homeostasis. Transgenic models indicate the importance of MRAP in adrenal gland formation. Like MC3R and MC4R knockout mice, MRAP2 knockout mice have an obese phenotype. In vitro studies indicate that MRAP2 enhances the MC3 and MC4 response to the agonist αMSH, which, like ACTH, is produced through precursor polypeptide proopiomelanocortin (POMC) cleavage. Analysis of cohorts of individuals with obesity have revealed several MRAP2 genetic variants with loss of function mutations which are causative of monogenic hyperphagic obesity with hyperglycaemia and hypertension. MRAP2 may also be associated with female infertility. This review summarises current knowledge of MRAP and MRAP2, their influence on GPCR signalling, and focusses on pathophysiology, particularly familial glucocorticoid deficiency type-2 and obesity.

Genetic Analysis of 25 Patients with 5α-Reductase Deficiency in Chinese Population.

BACKGROUND: A deficiency in steroid 5α-reductase type 2 is an autosomal recessive disorder. Affected individuals manifested ambiguous genitalia, which is caused by decreased dihydrotestosterone (DHT) synthesis in the fetus. METHODS: We analyzed 25 patients with 5α-reductase deficiency in China. Seventeen of the 25 patients (68%) were initially raised as females. Sixteen patients changed their social gender from female to male after puberty. RESULTS: Eighteen mutations were identified in these patients. p.Gly203Ser and p.Gln6∗ were found to be the most prevalent mutations. On the basis of the genotype of these patients, we divided them into different groups. There was no significant difference in hormone levels and external masculinization score (EMS) in patients with or without these prevalent mutations. Twelve common single-nucleotide polymorphisms (SNPs) near the p.Gln6∗ mutation were chosen for haplotype analysis. Three haplotypes were observed in 6 patients who had the p.Gln6∗ mutation (12 alleles). CONCLUSION: We analyzed mutations of the SRD5A2 gene in Chinese patients with 5α-reductase deficiency. Although hotspot mutations exist, no founder effect of prevalent mutations in the SRD5A2 gene was detected in the Chinese population.

New tight junction protein 2 variant causing progressive familial intrahepatic cholestasis type 4 in adults: A case report.

BACKGROUND: Progressive familial intrahepatic cholestasis (PFIC) encompasses a group of autosomal recessive disorders with high morbidity and mortality. Variants in the gene encoding tight junction protein-2 (TJP2) have been linked to PFIC type 4 (PFIC4), which predominantly presents in childhood. However, there are only limited data from adults with TJP2-related PFIC4. We report a family with an autosomal recessive disorder with a novel variant in the TJP2 gene in adults with very variable expression of PFIC4. CASE SUMMARY: The index patient presented at 19 years old with liver cirrhosis and variceal bleeding and was treated with endoscopic banding and beta-blockers. In 2018, he developed primary liver cancer that was treated with radiofrequency ablation followed by liver transplantation in 2019. Genetic testing revealed a novel homozygous TJP2 variant causing PFIC4 (TJP2([NM_004817.3]:c.[3334C>T]; [3334C>T])). The consanguineous family consists of the father and mother (both heterozygous) and their 12 children, of which five carry the variant in a homozygous state; however, these five siblings have highly variable expression of PFIC4. Two homozygous brothers had cirrhosis and portal hypertension at diagnosis at the ages of 19 and 36. Two other homozygous brothers, age 23 and 19, and the homozygous sister, age 21, have elevated liver enzymes but presently no cirrhosis, which may suggest an age-dependent penetrance. In addition, five sisters had severe and mild intrahepatic cholestasis of pregnancy and carry the TJP2 variant in a homozygous and heterozygous state, respectively. CONCLUSION: This novel TJP2 variant is associated with PFIC4 causing severe liver disease with cirrhosis and primary liver cancer in adolescents/adults.

New insights into 5α-reductase type 2 deficiency based on a multi-centre study: regional distribution and genotype-phenotype profiling of SRD5A2 in 190 Chinese patients.

BACKGROUND: The 5α-reductase type 2 (5α-RD2) deficiency caused by mutations in the steroid 5α-reductase 2 (SRD5A2) gene results in variable degrees of undervirilisation in patients with 46,XY disorders of sex development. This study aims to profile the regional distribution and phenotype-genotype characteristics of SRD5A2 in a large Chinese 5α-RD2 deficiency cohort through multi-centre analysis. METHODS: 190 subjects diagnosed with 5α-RD2 deficiency were consecutively enrolled from eight medical centres in China. Their clinical manifestations and genetic variants were analysed. RESULTS: Hypospadias (isolated or combined with microphallus and/or cryptorchidism) was fairly common in the enrolled subjects (66.32%). 42 variants, including 13 novel variants, were identified in SRD5A2. Homozygous and compound heterozygous mutations presented in 38.42% and 61.58% of subjects, respectively, and predominated in exons 1, 4 and 5. The most prevalent variant was c.680G > A (52.37%), followed by c.16C > T, (10.79%), c.607G > A, (9.21%) and c.737G > A, (8.95%). However, their distributions were different: c.680G > A was more common in South China than in North China (62.62% vs 39.16%, p < 0.001), whereas the regional prevalence of c.16C > T was reversed (6.07% vs 16.87%, p = 0.001). Furthermore, c.680G > A prevailed in cases with normal meatus (68.75%) or distal hypospadias (66.28%), compared with those with proximal hypospadias (35.54%, p < 0.001). However, cases with proximal hypospadias showed a higher frequency of c.16C > T (20.48%) than those with normal meatus (3.13%) or distal hypospadias (3.49%, p < 0.001). CONCLUSIONS: This study profiled variable phenotypic presentation and wide mutational spectrum of SRD5A2, revealing its distinctive regional distribution in Chinese patients and further shaping the founder effect and genotype-phenotype correlation of SRD5A2.

Effects of pre- and post-pubertal dihydrotestosterone treatment on penile length in 5α-reductase type 2 deficiency.

Steroid 5α-reductase type 2 deficiency (5αRD2) is a congenital disorder of sex development caused by impairment of conversion from testosterone (T) to 5α-dihydrotestosterone (DHT). DHT deficiency leads to various degrees of undervirilized external genitalia including micropenis, primarily correlated with mutations of the SRD5A2 gene that encodes 5α-reductase type 2. Four Japanese boys with isolated micropenis were diagnosed as 5αRD2 by elevated ratios of serum T/DHT, and decreased ratios of urinary 5α/5ß-reduced steroid metabolites. Genetic analyses for SRD5A2 identified that the four patients shared a hypomorphic mutation R227Q that has a residual activity related to the mild-form of 5αRD2. For prepubertal micropenis, DHT was transdermally applied to the four patients at the ages of 4-11 year, increasing a median of stretched penile lengths (SPLs) from 2.6 cm (-2.5 SD) to 4.4 cm (-0.2 SD). Nevertheless, the post-pubertal penile growth was apparently retarded, despite normal levels of T secreted from well-developed testes. The second course of DHT treatment underwent at ages of 12-18 year, but unable to normalize SPLs at a range of 6.0 to 7.0 cm (-3.4 to -2.4 SD). The prostate volumes of two patients were variable at 8.1 and 21 cm3, and a sperm cell count of one patient was normal as young adult. DHT treatment contributes to development of the penis and prostate, which are favorable for the potential fertility of 5αRD2 adults. Meanwhile, the retarded penile growth and a risk of prostate overgrowth may complicate the post-pubertal management with DHT for 5αRD2 males.

Identification of three novel SRD5A2 mutations in Chinese patients with 5α-reductase 2 deficiency.

In this study, we investigated the genetics, clinical features, and therapeutic approach of 14 patients with 5α-reductase deficiency in China. Genotyping analysis was performed by direct sequencing of PCR products of the steroid 5α-reductase type 2 gene (SRD5A2). The 5α-reductase activities of three novel mutations were investigated by mutagenesis and an in vitro transfection assay. Most patients presented with a microphallus, variable degrees of hypospadias, and cryptorchidism. Eight of 14 patients (57.1%) were initially reared as females and changed their social gender from female to male after puberty. Nine mutations were identified in the 14 patients. p.G203S, p.Q6X, and p.R227Q were the most prevalent mutations. Three mutations (p.K35N, p.H162P, and p.Y136X) have not been reported previously. The nonsense mutation p.Y136X abolished enzymatic activity, whereas p.K35N and p.H162P retained partial enzymatic activity. Topical administration of dihydrotestosterone during infancy or early childhood combined with hypospadia repair surgery had good therapeutic results. In conclusion, we expand the mutation profile of SRD5A2 in the Chinese population. A rational clinical approach to this disorder requires early and accurate diagnosis, especially genetic diagnosis.

Isolated glucocorticoid deficiency: Genetic causes and animal models.

Hereditary adrenocorticotropin (ACTH) resistance syndromes encompass the genetically heterogeneous isolated or Familial Glucocorticoid Deficiency (FGD) and the distinct clinical entity known as Triple A syndrome. The molecular basis of adrenal resistance to ACTH includes defects in ligand binding, MC2R/MRAP receptor trafficking, cellular redox balance, cholesterol synthesis and sphingolipid metabolism. Biochemically, this manifests as ACTH excess in the setting of hypocortisolaemia. Triple A syndrome is an inherited condition involving a tetrad of adrenal insufficiency, achalasia, alacrima and neuropathy. FGD is an autosomal recessive condition characterized by the presence of isolated glucocorticoid deficiency, classically in the setting of preserved mineralocorticoid secretion. Primarily there are three established subtypes of the disease: FGD 1, FGD2 and FGD3 corresponding to mutations in the Melanocortin 2 receptor MC2R (25%), Melanocortin 2 receptor accessory protein MRAP (20%), and Steroidogenic acute regulatory protein STAR (5-10%) respectively. Together, mutations in these 3 genes account for approximately half of cases. Whole exome sequencing in patients negative for MC2R, MRAP and STAR mutations, identified mutations in minichromosome maintenance 4 MCM4, nicotinamide nucleotide transhydrogenase NNT, thioredoxin reductase 2 TXNRD2, cytochrome p450scc CYP11A1, and sphingosine 1-phosphate lyase SGPL1 accounting for a further 10% of FGD. These novel genes have linked replicative and oxidative stress and altered redox potential as a mechanism of adrenocortical damage. However, a genetic diagnosis is still unclear in about 40% of cases. We describe here an updated list of FGD genes and provide a description of relevant mouse models that, despite some being flawed, have been precious allies in the understanding of FGD pathobiology.

Molecular genetics and phenotype/genotype correlation of 5-α reductase deficiency in a highly consanguineous population.

CONTEXT AND OBJECTIVES: 5-α reductase deficiency is a rare 46,XY disorder of sex development. We present detailed phenotypic and genotypic features of a cohort of 24 subjects from a highly consanguineous population of Saudi Arabia SUBJECTS AND METHODS: We studied the clinical presentation and hormonal profiles of 24 subjects diagnosed with 5-α reductase deficiency and performed genetic testing on DNA isolated from their peripheral blood using polymerase chain reaction and direct sequencing of the SRD5A2. RESULTS: All subjects had 46,XY karyotype and presented with atypical appearance of external genitalia ranging from clitoromegaly, micophallus with hypospadias, undescended testes to completely normally looking female genitalia. Thirteen (54%) of them had severe under virilization and were assigned female sex at birth. The other 11 subjects were raised as males. Stimulated Testosterone:Dihydrotestosterone ratio was high in all 16 subjects in whom it was measured. The genetic testing revealed 2 nonsense mutations (p.R103X and p.R227X) in 2 unrelated subjects, 3 missense mutations (p.P181L, p.A228T, p.R246Q) in 11 subjects and a splice site mutation (IVS1-2A > G) in 11 other subjects. There was significant phenotypic variability even in subjects with the same mutation and also within the same family. CONCLUSION: This is the first and largest report of the clinical and molecular genetics of 5-α reductase deficiency from the Middle East. It shows weak genotype/phenotype correlation and significant phenotypic heterogeneity. IVS1-2A > G mutation is the most common mutation and is likely to be a founder mutation in this part of the world.

Identification of three novel SRD5A2 mutations in Chinese patients with 5α-reductase 2 deficiency / 亚洲男科学杂志(英文版)

In this study, we investigated the genetics, clinical features, and therapeutic approach of 14 patients with 5α-reductase deficiency in China. Genotyping analysis was performed by direct sequencing of PCR products of the steroid 5α-reductase type 2 gene (SRD5A2). The 5α-reductase activities of three novel mutations were investigated by mutagenesis and an in vitro transfection assay. Most patients presented with a microphallus, variable degrees of hypospadias, and cryptorchidism. Eight of 14 patients (57.1%) were initially reared as females and changed their social gender from female to male after puberty. Nine mutations were identified in the 14 patients. p.G203S, p.Q6X, and p.R227Q were the most prevalent mutations. Three mutations (p.K35N, p.H162P, and p.Y136X) have not been reported previously. The nonsense mutation p.Y136X abolished enzymatic activity, whereas p.K35N and p.H162P retained partial enzymatic activity. Topical administration of dihydrotestosterone during infancy or early childhood combined with hypospadia repair surgery had good therapeutic results. In conclusion, we expand the mutation profile of SRD5A2 in the Chinese population. A rational clinical approach to this disorder requires early and accurate diagnosis, especially genetic diagnosis.

Infant cholestasis patient with a novel missense mutation in the AKR1D1 gene successfully treated by early adequate supplementation with chenodeoxycholic acid: A case report and review of the literature.

Steroid 5ß-reductase [aldo-keto reductase family 1 member D1 (AKR1D1)] is essential for bile acid biosynthesis. Bile acid deficiency caused by genetic defects in AKR1D1 leads to life-threatening neonatal hepatitis and cholestasis. There is still limited experience regarding the treatment of this disease. We describe an infant who presented with hyperbilirubinemia and coagulopathy but normal bile acid and γ-glutamyltransferase. Gene analysis was performed using genomic DNA from peripheral lymphocytes from the patient, his parents, and his elder brother. The patient was compound heterozygous for c.919C>T in exon 8 and exhibited a loss of heterozygosity of the AKR1D1 gene, which led to an amino acid substitution of arginine by cysteine at amino acid position 307 (p.R307C). Based on these mutations, the patient was confirmed to have primary 5ß-reductase deficiency. Ursodeoxycholic acid (UDCA) treatment did not have any effect on the patient. However, when we changed to chenodeoxycholic acid (CDCA) treatment, his symptoms and laboratory tests gradually improved. It is therefore crucial to supplement with an adequate dose of CDCA early to improve clinical symptoms and to normalize laboratory tests.

Childhood Sex-Typed Behavior and Gender Change in Individuals with 46,XY and 46,XX Disorders of Sex Development: An Iranian Multicenter Study.

Disorders of sex development (DSD) are congenital conditions in which the typical genetic and hormonal profiles are affected and thereby the usual process of sexual differentiation. Most of these studies, however, have been conducted in Western countries. In the present study, preschool sex-typed activities of Iranian individuals with DSD and their age-matched non-affected male and female relatives were assessed using the Pre-School Activities Inventory (PSAI) modified for retrospective self-report. A total of 192 individuals participated in our study, including 33 46,XX individuals with congenital adrenal hyperplasia (CAH; M age = 10.36, SD = 5.52), 15 46,XY individuals with complete androgen insensitivity syndrome (CAIS; M age = 19.8, SD = 7.14), and 16 46,XY individuals with 5-alpha reductase deficiency type-2 (5α-RD-2; M age = 17.31, SD = 7.28), as well as one age-matched non-affected male and female relative for each patient. With regard to PSAI scores, male-identifying participants with 5α-RD-2 and male controls reported similar levels of male-typical childhood play. Female-identifying participants with 5α-RD-2 and CAH showed comparable scores: significantly less masculine and more feminine than male controls, but significantly more masculine and less feminine than females with CAIS and female controls. These findings support the role of androgens in the development of sex-typical childhood play behavior, with those being exposed to higher levels of fetal functional androgens expressing more masculine behavior at preschool ages.

Genetic testing for familial hypercholesterolemia among survivors of acute coronary syndrome.

BACKGROUND: Familial hypercholesterolemia could be prevalent among patients with acute coronary syndrome. OBJECTIVE: To investigate both the frequency of causative mutations for familial hypercholesterolemia (FH) and the optimal selection of patients for genetic testing among patients with an acute coronary syndrome (ACS). METHODS: One hundred and sixteen patients with an ACS during 2009-2015 were identified through the SWEDEHEART registry. Patients who had either a high total cholesterol level ≥7 mmol L-1 combined with a triglyceride level ≤2.6 mmol L-1 , or were treated with lipid-lowering medication and had a total cholesterol level >4.9 mmol L-1 and a triglyceride level ≤2.6 mmol L-1 were included. Genetic testing was performed first with a regionally designed FH mutation panel (118 mutations), followed by testing with a commercially available FH genetic analysis (Progenika Biopharma). RESULTS: A total of 6.9% (8/116) patients had a FH-causative mutation, all in the LDL-receptor. Five patients were detected on the panel, and further testing of the remaining 111 patients detected an additional 3 FH-causative mutations. Baseline characteristics were similar in FH-positive and FH-negative patients with respect to age, gender, prior ACS and diabetes. Patients with a FH-causative mutation had higher Dutch Lipid Clinical Network (DLCN) score (5.5 (5.0-6.5) vs 3.0 (2.0-5.0), P < 0.001) and a higher low-density lipoprotein level (5.7 (4.7-6.5) vs 4.9 (3.5-5.4), P = 0.030). The Dutch Lipid Clinical Network (DLCN) score had a good discrimination with an area under the curve of 0.856 (95% CI 0.763-0.949). CONCLUSION: Genetic testing for FH should be considered in patients with ACS and high DLCN score.

5-α-Reductase type 2 deficiency: is there a genotype-phenotype correlation? A review.

5-α-Reductase type 2 enzyme catalyzes the conversion of testosterone into dihydrotestosterone, a potent androgen responsible for male sexual development during the fetal period and later during puberty. Its deficiency causes an autosomal recessive disorder of sex development characterized by a wide range of under-virilization of external genitalia in patients with a 46,XY karyotype. Mutations in the SRD5A2 gene cause 5-α-Reductase deficiency; although it is an infrequent disorder, it has been reported worldwide, with mutational heterogeneity. Furthermore, it has been proposed that there is no genotype-phenotype correlation, even in patients carrying the same mutation. The aim of this review was to perform an extensive search in various databases and to select those articles with a comprehensive genotype and phenotype description of the patients, classifying their phenotypes using the external masculinization score (EMS). Thus, it was possible to objectively compare the eventual genotype-phenotype correlation between them. The analysis showed that for most of the studied mutations no correlation can be established, although the specific location of the mutation in the protein has an effect on the severity of the phenotype. Nevertheless, even in patients carrying the same homozygous mutation, a variable phenotype was observed, suggesting that additional genetic factors might be influencing it. Due to the clinical variability of the disorder, an accurate diagnosis and adequate medical management might be difficult to carry out, as is highlighted in the review.

Clinical and molecular characterization of 5α-reductase type 2 deficiency due to mutations (p.Q6X, p.R246Q) in SRD5A2 gene.

Early diagnosis and optimal management for steroid 5α-reductase type 2 deficiency (5α-RD2) patients are major challenges for clinicians and mutation analysis for the 5α-reductase type 2 (SRD5A2) gene is the golden standard for the diagnosis of the disease. In silico analysis of this enzyme has not been reported due to the lack of appropriate model. Moreover, the histological and pathological changes of the gonads are largely unknown. In the present study, a 5α-RD2 patient born with abnormal external genitalia was studied and mutation analysis for SRD5A2 gene was conducted. Moreover, we constructed the homology modeling of 5α-reductase using SWISS-MODEL, followed by the molecular docking study. Furthermore, immunohistochemical staining of Ki67 for the testes tissue was conducted to investigate the potential pathological characteristics. The patient had male (46, XY) chromosomes but presented female characteristics, and the mutation analysis identified a heterozygotes mutation (p.Q6X, p.R246Q) in SRD5A2 gene. In silico analysis elucidated the potential effect of the mutation on enzyme activity. Immunohistochemical staining for the excised testes showed that 30%-50% of the germ cells were Ki67 positive, which indicated the early neoplastic potential. In conclusion, we analyzed the genotype-phenotype correlations of 5α-RD2 caused by a heterozygotes mutation (p.Q6X, p.R246Q). Importantly, we conducted the homology modeling and molecular docking for the first time, which provided a homology model for further investigations. Immunohistochemical results suggested gonadectomy or testis descent should be performed early for 5α-RD2 patient, as delayed treatment would have maintained the testes in a tumorigenic condition.

Comparison between two inhibin B ELISA assays in 46,XY testicular disorders of sex development (DSD) with normal testosterone secretion.

BACKGROUND: Inhibin B is a hormone produced by the Sertoli cells that can provide important information for the investigation of disorders of sex development (DSD) with 46,XY karyotype. The aim of this study is to compare two enzyme-linked immunosorbent assay (ELISA) assays for dosage of serum inhibin B in patients with 46,XY DSD with normal testosterone secretion. METHODS: Twenty-nine patients with 46,XY DSD and normal testosterone secretion (partial androgen insensitivity syndrome [PAIS] [n=8]; 5α-reductase deficiency [n=7] and idiopathic 46,XY DSD [n=14]) were included. Molecular analysis of the AR and SRD5A2 genes were performed in all patients and the NR5A1 gene analysis in the idiopathic group. Measurements of inhibin B were performed by two second-generation ELISA assays (Beckman-Coulter and AnshLabs). Assays were compared using the interclass correlation coefficient (ICC) and the Bland-Altman method. RESULTS: ICC was 0.915 [95% confidence interval (CI): 0.828-0.959], however, a discrepancy was observed between trials, which is more evident among higher values when analyzed by the Bland-Altman method. CONCLUSIONS: It is recommended to perform the inhibin B measurement always using the same ELISA kit when several evaluations are required for a specific patient.

Cryptogenic cholestasis in young and adults: ATP8B1, ABCB11, ABCB4, and TJP2 gene variants analysis by high-throughput sequencing.

BACKGROUND: Mutations in ATP-transporters ATPB81, ABCB11, and ABCB4 are responsible for progressive familial intrahepatic cholestasis (PFIC) 1, 2 and 3, and recently the gene for tight junction protein-2 (TJP2) has been linked to PFIC4. AIM: As these four genes have been poorly studied in young people and adults, we investigated them in this context here. METHODS: In patients with cryptogenic cholestasis, we analyzed the presence of mutations by high-throughput sequencing. Bioinformatics analyses were performed for mechanistic and functional predictions of their consequences on biomolecular interaction interfaces. RESULTS: Of 108 patients, 48 whose cause of cholestasis was not established were submitted to molecular analysis. Pathogenic/likely pathogenic mutations were found in ten (21%) probands for 13 mutations: two in ATP8B 1, six in ABCB11, two in ABCB4, three in TJP2. We also identified seven variants of uncertain significance: two in ATP8B1, one in ABCB11, two in ABCB4 and two in TJP2. Finally, we identified 11 benign/likely benign variants. Patients with pathogenic/likely pathogenic mutations had higher levels of liver stiffness (measured by FibroScan®) and bile acids, as well as higher rates of cholestatic histological features, compared to the patients without at least likely pathogenic mutations. The multivariate analysis showed that itching was the only independent factor associated with disease-causing mutations (OR 5.801, 95% CI 1.244-27.060, p = 0.025). CONCLUSIONS: Mutations in the genes responsible for PFIC may be involved in both young and adults with cryptogenic cholestasis in a considerable number of cases, including in heterozygous status. Diagnosis should always be suspected, particularly in the presence of itching.