17-KSR Deficiency

17-KSR deficiency or 17-beta Hydroxysteroid Dehydrogenase 3 Deficiency is an intersex variation that effects 1 in 147,000 newborn CTM or AMAB individuals (however those with this variation are also often incorrectly assigned female at birth as well.)

Most with this variation - despite their male chromosomes (XY) - have a vagina, ambiguous genitals, or a micropenis instead of a penis. Those who do have a penis usually have an oddly placed urethra. This means they often also have hypogonadism and aromatase excess syndrome.

Upon puberty, those with this variation usually gain muscle mass, have a deepening voice, facial and body hair, and possibly breasts as well. They usually are unable to produce fertile sperm, meaning reproduction is unlikely.

It is important to note that not all the symptoms listed above are guaranteed to occur in someone with this variation, as someone may only experience one or several of these symptoms, yet still hold the variation.

Causes
This variation is caused when the gene called HSD17B3 does not properly provide instructions to an enzyme that is active in testicle production. Because of this, one does not produce testosterone at the same level as males, and thus has more femininized traits outwardly.

17-KSR deficiency in Israel
In a specific area within Israel, incest and inbreeding is highly common, which causes the genetic development of many individuals to turn out in an unlikely manner. Because of this, 1 in every 100-150 individuals in this area were born with 17-KSR, which is a drastically high amount compared to the average rarity of the variation.

This does not mean that incestual relations is the reason for this variation, but rather means that it can intensify the likelihood of it in development.

Resources

 * https://medlineplus.gov/genetics/condition/17-beta-hydroxysteroid-dehydrogenase-3-deficiency/
 * https://pubmed.ncbi.nlm.nih.gov/17551466/
 * https://en.wikipedia.org/wiki/17%CE%B2-Hydroxysteroid_dehydrogenase_III_deficiency