Androgen Insensitivity Syndrome
Summary
Clinical characteristics.
Androgen insensitivity syndrome (AIS) is typically characterized by evidence of feminization (i.e., undermasculinization) of the external genitalia at birth, abnormal secondary sexual development in puberty, and infertility in individuals with a 46,XY karyotype. AIS represents a spectrum of defects in androgen action and can be subdivided into three broad phenotypes:
- Complete androgen insensitivity syndrome (CAIS), with typical female external genitalia
- Partial androgen insensitivity syndrome (PAIS) with predominantly female, predominantly male, or ambiguous external genitalia
- Mild androgen insensitivity syndrome (MAIS) with typical male external genitalia
Diagnosis/testing.
The diagnosis of AIS is established in an individual with a 46,XY karyotype who has: undermasculinization of the external genitalia, impaired spermatogenesis with otherwise normal testes, absent or rudimentary müllerian structures, evidence of normal or increased synthesis of testosterone and its normal conversion to dihydrotestosterone, and normal or increased luteinizing hormone (LH) production by the pituitary gland; AND/OR a hemizygous pathogenic variant in AR identified by molecular genetic testing.
Management.
Treatment of manifestations: To prevent testicular malignancy, treatment of CAIS may include either removal of the testes after puberty when feminization is complete or prepubertal gonadectomy accompanied by estrogen replacement therapy. Because the risk of malignancy is low, however, removal of gonads is increasingly controversial. Additional treatment for CAIS may include vaginal dilatation to avoid dyspareunia. Treatment of PAIS in individuals with predominantly female genitalia is similar to treatment of CAIS, but is more likely to include prepubertal gonadectomy to help avoid increasing clitoromegaly at the time of puberty. In individuals with PAIS and ambiguous or predominantly male genitalia, the tendency has been for parents and health care professionals to assign sex of rearing after an expert evaluation has been completed. Those individuals with PAIS who are raised as males may undergo urologic surgery such as orchiopexy and hypospadias repair. Those individuals with PAIS who are raised as females and who undergo gonadectomy after puberty may need combined estrogen and androgen replacement therapy. Males with MAIS may require mammoplasty for gynecomastia. A trial of androgen pharmacotherapy may help improve virilization in infancy. It is best if the diagnosis of AIS is explained to the affected individual and family in an empathic environment, with both professional and family support.
Prevention of secondary manifestations: Regular weight-bearing exercises and supplemental calcium and vitamin D are recommended to optimize bone health; bisphosphonate therapy may be indicated for those with evidence of decreased bone mineral density and/or multiple fractures.
Surveillance: Periodic reevaluation for gynecomastia during puberty in individuals assigned a male sex; monitoring of bone mineral density through DEXA scanning in adults.
Evaluation of relatives at risk: For an apparently asymptomatic older or younger sib who has normal external female genitalia and who has not yet undergone menarche, a karyotype can be done first. For those phenotypic females who have a 46,XY karyotype, molecular genetic testing for the known AR variant in the family can be pursued next. If the AR variant in the family is not known, androgen binding assays could be considered.
Genetic counseling.
AIS is inherited in an X-linked manner. Affected 46,XY individuals are almost always infertile. Each offspring of a female known to carry an AR pathogenic variant (heterozygote) is at a 25% risk for each of the following:
- Having a 46,XY karyotype and being affected
- Having a 46,XY karyotype and being unaffected
- Having a 46,XX karyotype and being a carrier
- Having a 46,XX karyotype and not being a carrier
Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if the pathogenic variant in the family is known.
Diagnosis
No formal diagnostic criteria for identifying AIS have as yet been published; large variance is seen at the molecular, biochemical, and morphologic levels due to the extreme variation in these characteristics with the various AIS phenotypes [Gottlieb et al 2012].
Suggestive Findings
Androgen insensitivity syndrome (AIS) should be suspected in an individual with the following clinical, family history, radiologic, and supportive laboratory findings.
Clinical features
- Absence of extragenital abnormalities
- Two nondysplastic testes
- Absent or rudimentary müllerian structures (i.e., fallopian tubes, uterus, and cervix) and the presence of a short vagina
- Undermasculinization of the external genitalia at birth
- Impaired spermatogenesis and/or somatic virilization (some degree of impaired virilization at puberty)
Family history of other affected individuals related to each other in a pattern consistent with X-linked inheritance. "Other affected family members" refers to:
- Affected 46,XY individuals;
- Manifesting heterozygous females (46,XX). About 10% of heterozygous females have asymmetric distribution and sparse or delayed growth of pubic and/or axillary hair.
Note: Absence of a family history of AIS or suggestive features of AIS does not preclude the diagnosis.
Radiology findings in the "predominantly male" phenotype (Table 2) including impaired development of the prostate and of the wolffian duct derivatives demonstrated by ultrasonography or genitourography
Supportive laboratory findings
- Normal 46,XY karyotype
- Evidence of normal or increased synthesis of testosterone (T) by the testes
- Evidence of normal conversion of testosterone to dihydrotestosterone (DHT)
- Evidence of normal or increased luteinizing hormone (LH) production by the pituitary gland
- In CAIS, but not in PAIS: possible reduction in postnatal (0-3 months) surge in serum LH and serum T concentrations [Bouvattier et al 2002]
- In the "predominantly male" phenotype (Table 2):
- Less than normal decline of sex hormone-binding globulin in response to a standard dose of the anabolic androgen, stanozolol [Sinnecker et al 1997]
- Higher than normal levels of anti-müllerian hormone during the first year of life or after puberty has begun
Establishing the Diagnosis
The diagnosis of AIS is established in a 46,XY proband with:
- Undermasculinization of the external genitalia, impaired spermatogenesis with otherwise normal testes, absent or rudimentary müllerian structures, evidence of normal or increased synthesis of testosterone and its normal conversion to dihydrotestosterone, and normal or increased LH production by the pituitary gland; AND/OR
- A hemizygous pathogenic variant in AR identified by molecular genetic testing (see Table 1).
Molecular genetic testing approaches can include single-gene testing, use of a multigene panel, and more comprehensive genomic testing:
- Single-gene testing. Sequence analysis of AR is performed first. Gene targeted deletion/duplication analysis to detect multiexon or whole-gene deletions or duplications may be considered if a pathogenic variant in AR is not identified by sequence analysis.
- A multigene panel that includes AR and other genes of interest (see Differential Diagnosis) may also be considered. Note: (1) The genes included in the panel and the diagnostic sensitivity of the testing used for each gene vary by laboratory and are likely to change over time. (2) Some multigene panels may include genes not associated with the condition discussed in this GeneReview; thus, clinicians need to determine which multigene panel is most likely to identify the genetic cause of the condition at the most reasonable cost while limiting identification of variants of uncertain significance and pathogenic variants in genes that do not explain the underlying phenotype. (3) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focused exome analysis that includes genes specified by the clinician. (4) Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests.For an introduction to multigene panels click here. More detailed information for clinicians ordering genetic tests can be found here.
- More comprehensive genomic testing (when available) including exome sequencing and genome sequencing may be considered if single-gene testing (and/or use of a multigene panel that includes AR) fails to confirm a diagnosis in an individual with features of AIS. Such testing may provide or suggest a diagnosis not previously considered (e.g., mutation of a different gene or genes that results in a similar clinical presentation). For an introduction to comprehensive genomic testing click here. More detailed information for clinicians ordering genomic testing can be found here.
Table 1.
Molecular Genetic Testing Used in Androgen Insensitivity Syndrome
| Gene 1 | Method | Proportion of 46,XY Probands w/a Pathogenic Variant 2 Detectable by Method |
|---|---|---|
| AR | Sequence analysis 3, 4 | ~95%-97% 5 |
| Gene-targeted deletion/ duplication analysis 6 | ~3%-5% 5 | |
Unknown 7
| See footnotes 6, 7, and 8 | |
CAIS = complete androgen insensitivity syndrome
PAIS = partial androgen insensitivity syndrome
MAIS = mild androgen insensitivity syndrome
- 1.
See Table A. Genes and Databases for chromosome locus and protein.
- 2.
See Molecular Genetics for information on allelic variants detected in this gene.
- 3.
Sequence analysis detects variants that are benign, likely benign, of uncertain significance, likely pathogenic, or pathogenic. Pathogenic variants may include small intragenic deletions/insertions and missense, nonsense, and splice site variants; typically, exon or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.
- 4.
Lack of amplification by PCR prior to sequence analysis can suggest a putative (multi)exon or whole-gene deletion on the X chromosome in affected males; confirmation requires additional testing by gene-targeted deletion/duplication analysis.
- 5.
androgendb
.mcgill.ca; www .hgmd.cf.ac.uk - 6.
Gene-targeted deletion/duplication analysis detects intragenic deletions or duplications. Methods used may include quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and a gene-targeted microarray designed to detect single-exon deletions or duplications.
- 7.
AR pathogenic variant detection frequency in individuals with MAIS is more difficult to assess because of the assumption that MAIS diagnoses are often missed: (1) In the presence of deficient or defective androgen binding activity in genital skin fibroblasts in an XY individual with clinical findings of CAIS and PAIS, the likelihood of finding a pathogenic variant in the androgen binding domain of AR approached 40% [Weidemann et al 1996]. (2) In the presence of normal androgen binding in genital skin fibroblasts in an XY individual with clinical findings of PAIS, the likelihood of finding an AIS-causing AR variant is 10% or less, even when exon 1 is screened and/or sequenced in its entirety [Author, personal observation]. (3) Because the presence of an AR pathogenic variant, not abnormal androgen binding, is now the primary diagnostic criterion for AIS, defective androgen binding activity in an XY individual with clinical findings of CAIS, PAIS, or MAIS who does not have an AR pathogenic variant may be inappropriately precluded from the above diagnostic categories [Gottlieb et al 2012, Lek et al 2014, Mongan et al 2015]. Indeed, it has now been suggested that a new category of 46,XY disorder of sex development be established, in which no AR variant is found, although AR binding may be impaired [Lek et al 2014]. However, this would appear to be premature in light of the discovery of a number of cases of somatic mosaicism and intra-tissue genetic heterogeneity [Gottlieb et al 2012].
- 8.
An informal survey of AIS databases in Canada, United States, and Great Britain showed that AR pathogenic variant detection frequency ranged from 65% to 95% in individuals with CAIS and from 40% to 45% in those with PAIS. The AIS database at the Lady Davis Institute for Medical Research (Montreal, Canada), which includes 138 individuals with CAIS or PAIS, reflects this variable detection rate [Gottlieb et al 2012]. Indeed, two additional reports have revealed a substantial percentage of individuals with putative PAIS in whom no AR variant has been found [Veiga-Junior et al 2012, Lek et al 2014].
Androgen binding assay. If molecular genetic testing fails to identify a pathogenic variant that can explain the affected individual’s phenotype, testing of a biopsy of genital skin for defective androgen binding may be considered. As a result of the increasing number of individuals with features of PAIS in whom no pathogenic AR variant is able to be identified, there has been an increase in demand for androgen binding assays to confirm the diagnosis of AIS.
Clinical Characteristics
Clinical Description
Androgen insensitivity syndrome (AIS) can be subdivided into three phenotypes: complete androgen insensitivity syndrome (CAIS), partial androgen insensitivity syndrome (PAIS), and mild androgen insensitivity syndrome (MAIS) (Table 2).
Table 2.
Classification of AIS Phenotypes
| Type | External Genitalia (Synonyms) | Findings |
|---|---|---|
| CAIS | Female ("testicular feminization") |
|
| PAIS | Predominantly female ("incomplete AIS") |
|
| Ambiguous |
| |
| Predominantly male |
| |
| MAIS | Male ("undervirilized male syndrome") |
|
Adapted from Sinnecker et al [1997]
Complete androgen insensitivity syndrome (CAIS). Individuals with CAIS have normal female external genitalia with absence of female internal genitalia. They typically present either before puberty with masses in the inguinal canal that are subsequently identified as testes or at puberty with primary amenorrhea and sparse to absent pubic or axillary hair. Breasts and female adiposity develop normally. Sexual identity and orientation are typically female and heterosexual.
CAIS almost always runs true in families; that is, affected XY relatives usually have normal female external genitalia and seldom have any sign of external genital masculinization, such as clitoromegaly or posterior labial fusion [Boehmer et al 2001]. On occasion, wolffian duct development is observed [Hannema et al 2004].
Partial AIS (PAIS) with predominantly female external genitalia presents in a manner similar to CAIS; however, affected individuals have signs of external genital masculinization including clitoromegaly or posterior labial fusion.
Partial AIS with ambiguous genitalia or predominantly male genitalia (PAIS, Reifenstein syndrome). Determining the sex of rearing may be an issue for children with frank genital ambiguity. In families with PAIS, phenotypic disparity may warrant male sex of rearing in one affected sib and female sex of rearing in another affected sib [Boehmer et al 2001, Chen et al 2015]. Individuals with PAIS and predominantly male genitalia are raised as males. Gynecomastia at puberty and impaired spermatogenesis occur in all individuals with PAIS. Pubic hair is usually moderate; facial, body, and axillary hair are often reduced.
Mild AIS (MAIS, undervirilized male syndrome). The external genitalia of affected individuals are unambiguously male. They usually present with gynecomastia at puberty. They may have undermasculinization that includes sparse facial and body hair and small penis. Impotence may be a complaint. Spermatogenesis may or may not be impaired. In some instances, the only observed abnormality appears to be male infertility [Gottlieb et al 2005]; therefore, MAIS could explain some cases of idiopathic male infertility [Goglia et al 2011].
MAIS almost always runs true in families.
Genotype-Phenotype Correlations
A correlation does exist among certain missense AR variants, their functional consequences, and external genital development, particularly in the case of CAIS (see the Androgen Receptor Gene Mutations Database).
The correlation is much less clear in PAIS, in which interfamilial phenotypic variation is observed [Brinkmann & Trapman 2000, Boehmer et al 2001, Deeb et al 2005, Gottlieb et al 2012, Lek et al 2014].
The Androgen Receptor Gene Mutations Database includes 45 instances in which identical AR variants produce different AIS phenotypes [Gottlieb et al 2001a, Gottlieb et al 2012].
In some instances, the variable expressivity associated with a number of single-nucleotide variants may be attributed to somatic mosaicism rather than to the modifying influence of "background" genetic factors [Boehmer et al 1997, Holterhus et al 1997, Holterhus et al 2001, Köhler et al 2005]. See Gottlieb et al [2001b] for a detailed discussion of the possible role of somatic mosaicism as a cause of variable expressivity.
It remains to be determined whether specific missense variants can be correlated with normal or impaired spermatogenesis and with absence or presence of localized expressions of undervirilization (e.g., gynecomastia, high-pitched voice, impotence). Although specific variants associated with azoospermia have been reported [Zuccarello et al 2008, Mirfakhraie et al 2011], only a more extensive analysis of more cases of idiopathic male infertility is likely to identify definitive correlations. Melo et al [2010] noted that infertile males who do not produce sperm have a higher number of AR variants than do males with impaired sperm production. Idiopathic infertility cases were found in both oligospermic and azoospermic men who had AR-CAG repeat lengths that were either significantly shorter (15-18 CAG repeat lengths) or significantly longer (22-28) than normal (i.e., 19-21); see Gottlieb et al [2012] and Giagulli et al [2014].
Penetrance
No definitive data regarding penetrance exist, possibly because of under-ascertainment of affected individuals, particularly phenotypic but infertile males in whom AR molecular genetic testing may not be performed [Gottlieb et al 2005]. The problem is compounded by situations where there is a genotype-phenotype disconnect and when individuals with features of AIS are not found to have an identifiable AR pathogenic variant.
Nomenclature
The terms "testicular feminization" and androgen resistance syndrome are outdated and thus rarely used now.
Prevalence
Standard references quote a prevalence of 2:100,000 to 5:100,000 for complete AIS (CAIS) based on estimates derived from otherwise healthy phenotypic females found to have histologically normal inguinal or abdominal testes. A survey in the Netherlands over a ten-year period based on reported cases of AIS concluded that the minimal incidence was 1:99,000 [Boehmer et al 2001].
Partial AIS (PAIS) is at least as common as CAIS.
The prevalence of mild AIS (MAIS) has not yet been determined. However, it is much less frequently reported than CAIS and PAIS [Hughes et al 2012].
Differential Diagnosis
Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome (OMIM 277000) is diagnosed in phenotypic females who exhibit amenorrhea and have a partial or complete absence of the cervix, uterus, and vagina. Individuals with MRKH can be distinguished from those with CAIS by confirmation of a 46,XX karyotype [Sultan et al 2009].
Hypospadias resulting from an AR pathogenic variant (and thus a part of the spectrum of PAIS) cannot be distinguished from hypospadias resulting from other (largely undefined) causes by the examination of the genitalia alone. AR variants associated with hypospadias are likely rare.
MAIS caused by single-nucleotide variants of AR [Wang et al 1998] may be clinically indistinguishable from MAIS caused by expansion of the polymorphic CAG repeat in AR [Tut et al 1997]. Pathogenic expansion of this triplet repeat is the cause of spinal and bulbar muscular atrophy (SBMA), also known as Kennedy disease (see Genetically Related Disorders).
Undermasculinization of the external genitalia and pubertal undervirilization are components of many different syndromes that have no etiologic relation to AR. They may or may not have a pathogenic relation to the androgen receptor protein. The one exception is a contiguous gene deletion syndrome that includes the AR locus and results in intellectual disability and genital abnormalities [Davies et al 1997].
46,XY infants born small for gestational age may have clinical features of PAIS with no identifiable AR pathogenic variant. It has been suggested that this association be termed "XY DSD with fetal growth restriction, as yet unexplained" [Lek et al 2014].
A survey of the Androgen Receptor Gene Mutations Database suggests that AIS may be attributable to factors other than the presence of AR variants. Findings that suggest the presence of other identifiable diagnoses in 46,XY individuals with predominantly female, ambiguous, or predominantly male genitalia include the following:
- Elevated levels of testosterone precursors caused by a partial testosterone biosynthetic defect in which compensatory serum LH concentrations stimulate a normal plasma testosterone concentration
- The presence of müllerian duct derivatives as a result of a testicular organogenesis defect with impaired Sertoli cell production of anti-müllerian hormone
- The presence of wolffian duct-derived internal male reproductive structures that differentiate in response to testosterone, suggesting 5-α-reductase deficiency, a partial testosterone biosynthetic defect, or PAIS. 5-α-reductase deficiency (OMIM 264600) is the result of biallelic pathogenic variants in SRD5A2. The enzyme converts testosterone to dihydrotestosterone (DHT), which is primarily responsible for the development of the external genitalia before birth.
- A recent study has reported that some individuals with features of PAIS have been found to have biallelic pathogenic variants in HSD17B3, which causes 17-beta hydroxysteroid dehydrogenase III deficiency (OMIM 264300) [Phelan et al 2015].
Issues to consider in individuals with some, but not all, of the clinical features of AIS:
- Normal serum concentrations of T, DHT, and LH after birth do not prove that the concentration was normal during the critical period of fetal genital masculinization.
- Normal responsiveness to androgen after birth does not prove that it was normal before birth. That is, in utero delay in the acquisition of normal androgen biosynthesis or normal androgen sensitivity may lead to features consistent with androgen insensitivity.
- Subnormal sensitivity to androgen after birth may involve components of the overall androgen response system (AR-interacting proteins) beyond the androgen receptor itself.
Management
Evaluations Following Initial Diagnosis
To establish the extent of disease and the needs of an individual diagnosed with androgen insensitivity syndrome, a complete evaluation by specialists in disorders of sex development (DSDs), which can include specialists in endocrinology, urology, gynecology, clinical genetics, psychology, and psychiatry [Hughes et al 2006, Parisi et al 2007, Douglas et al 2010], is ideal.
Treatment of Manifestations
A number of clinicians have sought to establish a consensus statement on management of DSD including AIS [Hughes & Deeb 2006]. A number of publications have subsequently discussed best management of these disorders. See Diamond & Beh [2008] (full text), Douglas et al [2010] (full text), Pasterski et al [2010] (full text), Wiesemann et al [2010] (full text), and Hughes et al [2012] (full text).
Assignment of sex of rearing. The issue of sex assignment in infancy when the child is being evaluated for ambiguous genitalia is paramount. It requires informed decision making by parents and health care personnel and should be resolved as early as possible, after a multidisciplinary evaluation has been completed.
- Even in CAIS this may not always be easy. Cheikhelard et al [2008] evaluated 29 individuals with CAIS; it was recommended that gonads be retained at least until the completion of spontaneous puberty and the possibility of virilization be evaluated before management decisions are made.
- Psychological counseling and use of support groups can be of benefit [Cull & Simmonds 2010, Hughes et al 2012].
- Gender identity has become a topic of increasing importance due to the possibility of changes in sex assignment over time [Kolesinska et al 2014].
- Issues of sexual orientation regardless of gender phenotype have also become increasingly important to explore and discuss [Brunner et al 2016].
CAIS
A critical consideration of any surgical intervention is the nature and timing of such intervention; thus, surgeons need to be involved with the affected individuals and pediatrician in any such decisions [Purves et al 2008, Munoz & Swan 2010]. Vidal et al [2010] reviewed the evolution of surgical techniques for "feminization" and "masculinization" and their possible outcomes.
A common practice is to remove the testes after puberty when feminization of the affected individual is complete, since feminization occurs partly by testicular estrogen and partly by peripheral conversion of androgen to estrogen.
The rationale for postpubertal gonadectomy is that testicular malignancy, which develops at the usual rate for cryptorchid testes, seldom occurs before puberty [Hannema et al 2006]. Prepubertal gonadectomy is now only considered if inguinal testes are physically or esthetically uncomfortable, and if inguinal herniorrhaphy is necessary. In this event, estrogen replacement therapy is necessary to initiate puberty, maintain feminization, and avoid osteoporosis.
However, the issue of gonadectomy is controversial. Some have argued that the true risk for malignant transformation of the gonads is small and have suggested postpubertal gonad biopsy as opposed to removal [Hughes et al 2006, Parisi et al 2007, Patel et al 2016], which would allow affected individuals to retain a natural source of androgen production and avoid exogenous hormone replacement.
In one study of 48 individuals diagnosed with either CAIS or PAIS, gonadoblastomas were observed in 9/30 (30%) of individuals with CAIS and 3/18 (16%) of individuals with PAIS, suggesting that the risk of gonadal malignancy may be greater than previously reported; the authors suggest earlier rather than later prophylactic gonadectomy [Liu et al 2014]. Another study found the frequency of gonadal tumor in individuals with CAIS was 13/48 (27%) and in those with PAIS was 2/21 (9%), with similar conclusions regarding the time of gonadectomy [Jiang et al 2016].
Vaginal dilatation to augment vaginal length and to avoid dyspareunia is typically the treatment of choice for those with short vaginal length. If this method fails, new treatments of blind vagina have been proposed, including autologous buccal mucosal graft vaginoplasty and enhanced balloon vaginoplasty [Zhao et al 2009, El Saman et al 2011]. Recent studies that examined the long-term outcomes of vaginoplasty with autologous buccal micromucosa indicated a high degree of satisfaction [Li et al 2014]. In addition, a study reported that peritoneal vaginoplasty appeared to be superior to ileal vaginoplasty [Huang et al 2014]. However, surgical reconstruction frequently requires maintenance vaginal dilatation to decrease the likelihood of future stricture.
The question of how much and when to disclose the diagnosis of CAIS to an affected individual has not been resolved uniformly; however, it has become obvious that explanation of the diagnosis in an empathic setting is much preferable to systematic concealment or self-discovery of the diagnosis in an environment devoid of support from family, professionals, and other affected individuals [Conn et al 2005].
PAIS with Predominantly Female Genitalia (Incomplete AIS)
The issues are similar to those discussed under CAIS, except prepubertal gonadectomy helps avoid the emotional discomfort of increasing clitoromegaly at the time of puberty.
In instances in which the diagnosis of PAIS is difficult to establish because of the presence of somatic mosaicism, a change of sex assignment can result in concomitant problems [Köhler et al 2005].
PAIS with Ambiguous Genitalia or Predominantly Male Genitalia
The assignment of sex in an infant with ambiguous genitalia is a complex process that requires timely assessment by a multidisciplinary team in consultation with the family and should be resolved as early as possible. Aside from purely anatomic and surgical considerations, the choice of a male sex-of-rearing demands a therapeutic trial with pharmacologic doses of androgen to try to predict potential androgen responsiveness at puberty. Furthermore, appreciable phallic growth in response to administered androgen facilitates reconstructive surgery.
In instances in which maximum information is being gathered on an infant with no family history of AIS before sex is assigned, sequence analysis of AR may be considered; however, the lower probability of detecting an AR variant in individuals with the PAIS phenotype and the poor positive predictive value of any given variant regarding AIS phenotype need to be considered when making decisions about sex assignment.
It has also been reported that the length of the AR exon 1 CAG repeat can influence the efficacy of testosterone treatments: individuals with shorter repeat lengths are more likely to respond to hormonal treatments [Zitzmann 2009]. However, the efficacy of CAG repeat length as a possible marker to assess hormonal treatment must await further studies.
Based on experience with a small number of individuals, the role of long-term androgen pharmacotherapy in individuals with PAIS who are raised as males remains unclear. Response to androgen treatment may be substantial in individuals with certain missense variants in the DNA-binding domain of the androgen receptor [Weidemann et al 1998], and a recent study confirmed the difficulty of accurately predicting the efficacy of androgen treatment [Becker et al 2016]. Thus, considerable caution should be exercised with regard to androgen treatment [Werner et al 2010], in particular because special hormonal profiles to androgen insensitivity have often not been acknowledged in replacement strategies. It has been proposed that an external masculinization score in neonates could be a reasonable predictor of virilization at puberty in individuals with PAIS who have been assigned a male sex of rearing [Hughes et al 2012].
Gynecomastia that develops in puberty eventually requires reduction mammoplasty. It has been reported that tamoxifen has been used for treating pubertal gynecomastia in two sibs with PAIS [Saito et al 2014].
Those individuals with PAIS who are raised as females and who have gonadectomy after puberty may need combined estrogen and androgen replacement therapy, the latter to maintain libido.
MAIS
Men with MAIS often require reduction mammoplasty for treatment of gynecomastia.
A trial of androgen pharmacotherapy is recommended to attempt to improve virilization [Loy & Yong 2001].
Prevention of Primary Manifestations
The efficacy of androgen therapy in preventing manifestations such as gynecomastia is not clear.
Prevention of Secondary Manifestations
Women with CAIS have decreased bone mineral density, regardless of timing of gonadectomy [Oakes et al 2008]. However, women with PAIS who choose not to undergo gonadectomy do not appear to be at high risk for decreased bone mineral density [Bertelloni et al 2010].
- In addition to estrogen replacement therapy, supplemental calcium and vitamin D are recommended.
- Regular weight-bearing exercises are encouraged to maintain bone health.
- Bisphosphonate therapy may be indicated for those individuals with evidence of decreased bone mineral density and/or multiple fractures.
Surveillance
Appropriate measures include the following:
- Monitoring of postnatal development of genitalia that were ambiguous at birth for changes that could lead to reconsideration of the assigned sex
- For individuals assigned a male sex, evaluation during puberty for signs of gynecomastia
- In adults, monitoring of bone mineral density through DEXA (dual-emission x-ray absorptiometry) scanning [Oakes et al 2008]
Evaluation of Relatives at Risk
It is appropriate to evaluate the apparently asymptomatic older and younger sibs of a proband in order to identify as early as possible those who would benefit from institution of treatment and preventive measures.
- Evaluations can include karyotype in sibs who have normal external female genitalia but have not yet undergone menarche.
- Molecular genetic testing can be pursued next if a phenotypic female is found to have a 46,XY karyotype and if the AR variant in the family is known.
- Androgen binding assays may be considered if an AR variant has not been identified in the family.
See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.
Therapies Under Investigation
Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.
Other
Chen et al [2010] noted that Fkbp52 regulates AR transactivation activity and male urethra morphogenesis, suggesting that AR variants may require other genetic factors to produce hypospadias.
Apolipoprotein D (APOD) is a possible biomarker of AR function in AIS [Appari et al 2009].