Thursday, March 15, 2007
Well since we got started on this, might as well go all the way. Recently while researching a topic for a grant that I need to write for my class, I was looking for genetic diseases that affect brain development. I came across the "cat eye syndrome" which is of particular interest to me since it is a chromatin remodeling defect. This is when I discovered the concept of "ectopic" anus. Of course I held on to that knowledge waiting for the opportune moment during lunch. Another anal phenotype associated with the disease is imperforate anus, which is when the rectum finishes in a dead end, which thankfully can be corrected by surgery. Ectopic or malformed anuses can be a cause of constipation in neonates and this group devised a method to find and calculate the anal position index (API). Surprisingly out of 200 neonates 6 females and 5 males had abnormal scores on the API. There are also extremely rare cases of ectopic bowel segment in a boy with diphallus, or in a girl with rectovestibular fistula associated with occult distal vaginal atresia, or even vaginal anus. It turns out there is a whole spectrum of urino-genital ectopism which can cause all kinds of fertility problems, including ectopic pregnancy in the rectum à la "Twins", or ectopic testicles à la "South Park". Some of these genetic diseases that cause malformations can tell us a lot about the development of the uro-genital tract, and not surprisingly, HOX genes seem to be involved.