In April 2016, which is to say over three years ago, Talmudology wrote about polydactyly, when the Daf Yomi cycle studied Kiddushin 25. There we wrote: “We will discuss syndactyly when we study tractate Bechorot, (daf 45a), on June 1st, 2019, הבעל"ט” And here we are. Tomorrow, June 1st 2019 (which is Shabbat) we will learn Bechorot 45, and we are therefore delighted to keep our promise and explain syndactyly, which is the condition in which one or more adjacent digits are fused together. But first, have a quick re-read of that earlier post; it will help put this medical condition into perspective…….Done? OK then, here we go.
The Cohen with fused digits
Tomorrow we continue the discussion of physical abnormalities which would prohibit a Cohen from serving in the Temple. The Mishnah reads as follow:
אצבעותיו מורכבות זו על זו או קלוטות למעלה עד הפרק כשר למטה מן הפרק וחתכה כשר
A priest whose fingers or toes are configured one upon the other, or one whose fingers or toes are attached, is likewise disqualified. But if they were attached from above the palm of the hand or the bottom of the foot only until the middle joint, he is fit. If they were attached below the joint, higher up on the finger or toe, and he cut to separate them, he is fit.
The case here is a Cohen with, say two fingers or two toes that are fused together, so that it appears that there is a digit missing. The hand may look like this:
Or in extreme cases like this:
These photos are all obviously from young children, which is good news. Surgeons are able to separate the fused fingers or toes, generally when the infant is 1-2 years old, and so there are now few adults around in whom the condition went uncorrected.
The Classification of Syndactyly
Syndactyly (from the Greek syn = together; dactylos=digit) occurs in about 2-3 per 10,000 live births In 10-40% there is a family history of the condition and is twice as common among males (remember these facts for later). In about half of all cases there are bilateral and symmetrical fusions, and while it may be an isolated finding, in many cases it is part of a genetic disorder like Apert’s or Poland’s syndrome.
There are several different types and subtypes, depending on whether the condition is classified based on an anatomical approach, a genetic or molecular approach, a descriptive approach or an embryological classification. One classification, from a 2012 review of the topic published in The European Journal of Human Genetics, is shown below.
What Causes Syndactyly? It’s often the genes
Syndactyly sometimes runs in families, so in these cases a genetic cause was long suspected. For example, fusion of the fourth and fifth metacarpals (an uncommon type of syndactyly) was first described 1928 and was initially thought to have an X-linked recessive trait. It was later classified as an autosomal dominant inheritance, found in some families with male-male transmission as well as females affected. But we are now able to exactly pinpoint some of the genetic causes. Type I, Apert syndrome, is associated with the FGFR2 gene (to be exact the the loci 10q26). Type II, (Carpenter syndrome) is linked to RAB23 gene, and Type V, also known as Pfeiffer syndrome is been linked to the FGFR 1 and 2 genes.
Why did the Mishnah Discuss Syndactyly in Cohanim?
At first, the discussion of syndactyly as a disqualification for a Cohen seems rather odd. I mean really, how many cases could there have been? But the reason that the Mishnah spent time on this is now obvious. In many cases it is a genetic disorder, mostly affecting men. To be a Cohen you must be the child of a father who is a Cohen. As we have already learned, there are several “Cohen related genes,” and now we can add to the list the possibility that one of the many genetic causes of syndactyly was linked to those who were Cohanim, and who might pass the gene to their male children.
As we saw in an earlier post, the rabbis of the Mishnah and Talmud described different medical observations without realising that they originated from a single cause (like alcoholic liver disease) or had a genetic component. How lucky we are to have this knowledge at our fingertips (sorry). The rabbis would have wanted no less.
[Extra credit: The Wiki page on Syndactyly notes that “The earliest appreciation of syndactyly as a birth anomaly…can be traced back to the Andalusian Muslim surgeon Al-Zahrawi (d. 1013 CE).” This should obviously be corrected, since it was mentioned as a birth defect in the Mishnah, edited c. 200 CE, some eight hundred years earlier. Can someone please edit the page so that it is accurate? Thanks.]