Androgen insensitivity syndrome (AIS) is a clinical disease characterized by genotypic male person (with XY sex chromosomes) which becomes insensitive to androgens (male testosterone) and shows phenotypic traits of a female. AIS is formerly referred to as testicular feminization which is identified as an X-linked recessive condition that hampers normal physical masculinization among male patients.
The insensitivity of the subject to the virilizing hormone could either be complete or partial depending on the number of residual receptor function (androgen receptors). Patients suffering from complete androgen insensitivity syndrome (CAIS) will have a complete female external genitalia . Majority of these male patients will become infertile and develop gynecomastia, although, in rare cases of AIS loaded with substantial amounts of exogenous testosterone can becomes fertile again . Although complete cases of AIS may present with female external genitalia, the internal gonads like the testes are present in both complete and partial cases producing physiologically active amounts of testosterone in the serum.
Androgen insensitive syndrome is a genetic disease dispersed in the family tree in an X-linked recessive pattern of gene transmission. The mutated chromosome has been found in loci of the X sex chromosome in all cases of AIS. Because males have only one X chromosome, they are more prone to express the AIS traits compared to the female counterpart that has two X sex chromosomes. Although three fourths of the AIS carriers are females that is why genetic counselling with carrier mothers is a prudent preventive practice in its management.
There are no exact clinical data on the incidence AIS internationally. A Danish cohort study on hospitalized cases of AIS reveals an incidence rate of 1 case per 20,040 male live births. The complete form of AIS or CAIS appears to be more frequent than the partial AIS (PAIS) forms worldwide. An international study of sex development disorder registered an 11% incidence of AIS with genital anomalies and 5.2% has a confirmed androgen receptor mutation problem .
The basic pathogenesis in the development of AIS is on the mutation of the androgen receptor gene that results in a non-functional receptor for the androgen hormones. This androgen receptor gene has been localized in the X chromosome in the short arms of q11 to 13.
A complete gene deletion will eventually result in a complete AIS and an incomplete deletion will result in a partial AIS defect. Late onset AIS may occur in Kennedy disease where a bulbar atrophy results in androgen insensitivity presenting as postpubertal gynecomastia .
The general prognosis for complete AIS is practically good especially if the testicular tissue is removed in the right time and exogenous testosterone is adequately supplied. Patients with CAIS can live a normal life without any observable decrease in life expectancy. In partial AIS, prognosis depends on the appearance of the external and internal genitals.
The following clinical disorders are known complications of Androgen insensitivity syndrome:
The following symptomatology are found in complete and partial androgen insensitivity syndrome:
The following laboratories and test are routinely used in patients suspected of having androgen insensitivity syndrome:
The medical care of a patient suffering from androgen insensitive syndrome is conveniently divided into hormone replacement therapy (HRT) and psychological support . The common HRT agents used in AIS are testosterone and dihydrotestosterone (DHT), where DHT is noted to be more stable because it could not be aromatized to estrogen hormone in the serum.
Psychological support is the most important form of medical therapy for AIS to assist patients in coping with the social stigmata and psychological stresses brought about by the disorder . A pediatric psychologist is often times sought for to help the child overcome the age appropriate manner and cognitive functions.
The standard surgical care for patients with AIS is orchiectomy to prevent the malignant degeneration of the testes intraabdominally . By convention, orchiectomy is usually performed early in childhood to abate any psychological issues linked to gender identity and confusion with the child. Although the exact age where orchiectomy should be performed remains debatable at this point.
Androgen insensitive dyndrome among the neonates is not preventable; thus, there are no modifiable precautions that may be resorted to avert its expression. Given the dire complications like testicular cancers, the early diagnosis and removal of the testes from the abdomen is an imperative move in the prevention of AIS complications.
Genetic counselling for parents and carriers may reduce its incidence among offspring given that there is a 25% chance of AIS penetrance in the succeeding siblings from the same mother.
Androgen insensitivity syndrome (AIS) is a clinical disease characterized by genotypic male showing feminine physical traits due to androgen insensitivity.
The cause of androgen insensitivity syndrome is a mutation in the androgen receptor gene which is localized on the X chromosome.
Undescended testes, gynecomastia, absence of axillary and pubic hairs, and variable genital appearances are the symptoms of AIS.
Genetic karyotyping, testosterone assays, ultrasound imaging, and diagnostic laparotomy are done to diagnose AIS.
Treatment and follow-up
Hormonal replacement therapy, psychological support, and surgical orchiectomy are usually necessary to treat AIS and its possible complications.