Polydactyly

Bechorot 45b ~ Syndactyly, and Talmudology Keeps a Promise

Remember Polydactyly?

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:

בכורות לה,ב

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:

Palm view of classic simple syndactyly of left long and ring fingers. Over 50% of all webbed fingers occur like this.From  here .

Palm view of classic simple syndactyly of left long and ring fingers. Over 50% of all webbed fingers occur like this.From here.

maydeletesmaller.jpg

Or in extreme cases like this:

The hand of the patient with syndactyly of several digits. From Biesecker L.G. The Greig cephalopolysyndactyly syndrome.  Orphanet Journal of Rare Diseases 2008, 3:10

The hand of the patient with syndactyly of several digits. From Biesecker L.G.The Greig cephalopolysyndactyly syndrome. Orphanet Journal of Rare Diseases 2008, 3:10

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.

Schematic diagrams of syndactyly types (I-a–III). Shaded digits depict cutaneous fusion only, while bony synostosis is represented by black digital elements within the shaded area. The grey digital elements show hypoplastic phalanges or clinodactyly/brachydactyly. The digital elements with amorphous borders symbolize dysplastic bones. From Malik S. Syndactyly: phenotypes, genetics and current classification.  European Journal of Human Genetics  (2012) 20, 817–824;

Schematic diagrams of syndactyly types (I-a–III). Shaded digits depict cutaneous fusion only, while bony synostosis is represented by black digital elements within the shaded area. The grey digital elements show hypoplastic phalanges or clinodactyly/brachydactyly. The digital elements with amorphous borders symbolize dysplastic bones. From Malik S. Syndactyly: phenotypes, genetics and current classification. European Journal of Human Genetics (2012) 20, 817–824;

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.

A family with three generations of ring and small finger involvement, none of which was ever surgically corrected. From Flatt A. Webbed Fingers. In The Care of Congenital Hand Anomalies, 2nd ed. St. Louis: Quality Medical Publishing, Inc., 1994:228–275.

A family with three generations of ring and small finger involvement, none of which was ever surgically corrected. From Flatt A. Webbed Fingers. In The Care of Congenital Hand Anomalies, 2nd ed. St. Louis: Quality Medical Publishing, Inc., 1994:228–275.

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.]

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Kiddushin 25a ~ Polydactyly

קידושין כה, א–ב

 א"ר חייא בר אשי אמר רב היתה לו יתרת וחתכה עבד יוצא בהן לחירות, אמר רב הונא והוא שנספרת על גב היד

Rav Hiyyah bar Ashi said in the name of Rav: if a slave had an extra finger and his master cut it off, the slave is freed on account of this act. Rav Huna said this only applies if the extra finger is in line with the others [lit. counted alongside the hand].  

Polydactyly (from the Greek daktylos, meaning finger), is a developmental abnormality in which there are more than the customary five fingers or toes at the end of the arms and legs. It has long been recorded in ancient civilizations - and is even mentioned in our own Hebrew Bible. Do you know who is described there as having a total of twenty four fingers and toes? (Click here to find out.)

Polydactyly is classified by the location of the extra digit: If it is found on the thumb or big toe, it is called preaxial polydactyly. If it is found on the the little (fifth) finger or toe it is called postaxial polydactyly.  Accessory digits in-between are classified according to their location and where they join the hand or finger. Syndactyly, on the other hand (!) occurs when there are fewer than five fingers or toes on each limb. (We will discuss syndactyly when we study tractate Bechorot, (daf 45a), on June 1st, 2019,  הבעל"ט.)

Rav Huna's Classification, and Swanson's classification

There are many different ways to classify polydactyly - although the most commonly used is the 1964 Swanson classification system, a modified version of which was adopted by the American Society for Surgery of the Hand and the International Federation of Societies for Surgery of the Hand in 1976. 

But Rav Huna, who died in Babylon around the year 296 CE, developed his own classification system long before Swanson, and it is based on simple observation: does the extra digit seem to begin in line with the other fingers, or does its origin seem to lie above them?  For Rav Huna, an extra digit that originated beyond the metacarpal-phalyngeal joint (the knuckle for our non-medical reader) in the hand, or beyond the metatarsal-phalageal joint in the foot did not have the legal status of a normal digit.  So an act of assault by the owner of a slave in which this kind of digit was amputated would not legally count as sufficient cause to allow the slave to gain his freedom.  With this information, look at the drawings below and decide in which case the loss of the extra digit would be sufficient cause for the slave to be freed.

Various forms of postaxial (ie. not on the big toe) Type A polydactyly of the foot, ranging from a partially duplicated fifth intermediate phalanx (top left) to a fully developed sixth digit, including the metatarsal (bottom right). From Case DT. Hill RJ. Merbs CF. Fong M. Polydactyly in the Prehistoric American Southwest.    Journal of Osteoarchaeology   2006: 6: 221–235.

Various forms of postaxial (ie. not on the big toe) Type A polydactyly of the foot, ranging from a partially duplicated fifth intermediate phalanx (top left) to a fully developed sixth digit, including the metatarsal (bottom right). From Case DT. Hill RJ. Merbs CF. Fong M. Polydactyly in the Prehistoric American Southwest.  Journal of Osteoarchaeology 2006: 6: 221–235.

If the slave had an extra fifth toe outlined in Figures 2-6, its loss would result in the slave going free. In all these cases, the extra digit arises in line with the base the the other toes (and in Figure 6, the extra toe is joined to an extra metatarsal). But in Figure 1, the extra fifth digit arises from the distal end of the fifth distal phalange (or, for our non-medical reader, the tip of the pinky); in this case its traumatic amputation by the slave's owner would not result in the slave gaining his freedom. 

This categorization appears to be another previously unrecognized medical first in the Talmud: Rav Huna's classification of polydactyly.   

היתה לו אצבע יתירה וחתכה, אם עומדת בסדר האצבעות יוצא לחירות
— שולחן ערוך יורה דעה הלכות עבדים סימן רסז סעיף כט
Polydactylous feet from Newspaper Rock in Indian Creek State Park, Utah. These carvings in rock are called petroglyphs, and were made by native Americans as long as  1,500  years ago .

Polydactylous feet from Newspaper Rock in Indian Creek State Park, Utah. These carvings in rock are called petroglyphs, and were made by native Americans as long as 1,500  years ago.

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