The AMHR2 gene encodes the anti-Müllerian hormone (AMH) receptor type 2 that is involved in male sex differentiation. The AMH receptor type 2 is found on the surface of Müllerian duct cells. These cells are found in both male and female fetuses, and they are the precursor to the female reproductive organs. AMHR2 is an essential factor for the regression of the Müllerian duct in males. During development of male fetuses, AMH and testosterone are produced in the testes by different cells and have different effects. Testosterone promotes the development of male genitalia while the AMH protein binds to the AMH receptor type 2, which signals apoptosis of the Müllerian duct cells. As a result, the Müllerian duct regresses in males. Defects in the AMH receptor type 2 lead to the persistent Müllerian duct syndrome, a rare form of male pseudohermaphroditism characterized by a failure of Muellerian duct regression and becomes a uterus and fallopian tubes in otherwise normal males.
The AMHR2 gene is located in chromosome 12q13. AMHR2 contains 11 exons spanning approximately 8 kb within the genomic DNA. The encoded protein comprises 573 amino acids with a molecular mass of 63 kDa. More than 27 mutations have been described in this gene in patients with persistent Muellerian duct syndrome type 2. The most common mutation that occurs in about half the patients is a deletion of 27 nucleotides.
See: [Saudi Arabia> Abduljabbar et al. (2012)]
Abduljabbar et al. (2012) described two extended Saudi and Jordanian families affected with persistent Müllerian duct syndrome due to mutations in the AMH receptor type II. The parents of the Saudi family were first cousins. They had 6 sons and 2 daughters; 4 of the boys and one girl were homozygous for a stop codon mutation (c.6053C>T) in exon 9. The proband presented with bilateral undescended testes at birth and developed left inguinal hernia at the age of 1 year. Four months later, he underwent orchiopexy and hernia repair. Both testes with a uterus, cervix, and fallopian tubes could be pulled into the left scrotum through a left inguinal incision. His three older brothers had undergone prior surgery. His remaining two brothers and both sisters were clinically normal. The parents of the Jordanian family were not related; they had 4 girls and 2 boys. One boy and one girl were homozygous for a transversion mutation (c.1973 C>G) in exon 6. The proband was a 2 day-old boy presented with impalpable testes. At the age of 9 months, laparoscopy showed a left inguinal hernia containing both testes with a uterus and cervix. They were returned to the abdominal cavity and the uterus was dissected and removed, then the testes were fixed intro the scrotum. His 4 sisters and brother were clinically normal.
Al-Faris et al., (2016) described a 14-month-old Saudi boy with Persistent Müllerian duct syndrome. He presented at 27 days of age with swelling in the right groin area, which was irreducible to the inguinal canal. Also redness on the skin of the right groin area was observed that extended to the right scrotum. He underwent a surgery wherethe testis was pulled down to the scrotum in the normal anatomical position. His left testis was not palpable in the scrotum or in the groin area. After a year, he underwent right orchidopexy and left testis exploration that revealed small left intra-abdominal gonads in a position similar to ovary, a small uterus and vagina in the midline. The biopsy and histology of tissue revealed immature testicular tissues. MRI of the pelvis showed normal male urethra with the presence of a small uterus and vagina but no definite testicle or ovaries. Genetic testing revealed a homozygous c.994C>T mutation in the AMHR2 gene.
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