Generality
Polydactyly is a congenital physical anomaly, characterized by the presence, in the hands or feet (or both), of a number of fingers greater than 5.
There are at least 3 types of polydactyly:
- the preassial polydactyly, in which the supernumerary finger (s) sprout from the side of the thumb / big toe;
- post-axial polydactyly, in which the supernumerary finger (s) sprout from the side of the little finger / fifth toe;
- finally, the central polydactyly, in which the supernumerary fingers or fingers sprout from the central fingers of the hand or foot.
Various treatments exist: the choice of the most appropriate depends on the characteristics of the additional fingers and the doctor's evaluations in the diagnostic field.
Recalls of genetics
Before proceeding with the description of polydactyly, it is useful to review some fundamental concepts of genetics.
What are chromosomes? According to the definition, chromosomes are the structural units in which DNA is organized. The human cells contain, in their nucleus, 23 pairs of homologous chromosomes (22 of an autosomal non-sexual type and a couple of sexual type); each pair is different from another, as it contains a specific gene sequence.
What are genes? They are short stretches, or sequences, of DNA with a fundamental biological meaning: from them, in fact, proteins are derived, that is, fundamental biological molecules for life. In genes, there is "written" part of what we are and what we will become.
Each gene is present in two versions, the alleles: an allele is of maternal origin, then transmitted by the mother; the other allele is of paternal origin, therefore transmitted by the father.
What is polydactyly?
Polydactyly is the medical term that refers to a congenital physical anomaly, characterized by the presence, in the hands, feet or both, of a number of fingers greater than 5.
Thus, an individual with polydactyly is a person who owns, in the hands and / or feet, 6 or more fingers.
The doctors refer to the "extra fingers" using the terms: extra finger (or fingers), supernumerary finger (or fingers) or supernumerary finger (or fingers).
ORIGIN OF THE NAME
The word polydactyly derives from the union of two terms of Greek origin: "polys" (πολύς), which means "many" "many", and "daxtylos" (δάκτυλος), which means "finger".
Thus, the literal meaning of polydactyly is "many fingers".
SYNONYMS OF POLYDACTYLIA
Two synonyms of polydactyly, very little used, are: hyperdattilia (" iper- " is a prefix indicating overabundance) and polydactylism.
IT IS THE CONTRARY OF OLIGODACTYLIA
Polydactyly is the condition contrary to oligodactyly, which consists in the presence of a number of fingers, in hands and / or feet, less than 5.
The prefix "oligo-" derives from the Greek word "oligos" (ὀλίγος ‚), which means" little ".
TYPES OF POLYDACTYLIA
Doctors have deemed it appropriate to classify polydactyly into three different types, depending on where the finger or supernumerary fingers reside.
These three types are called:
- Preassed polydactyly . It occurs when the extra finger or fingers sprout from the side of the thumb (in the hand) or the big toe (in the foot).
In this case, the preassial polydactyly that affects the hand is called radial preassial polydactyly (or more simply radial polydactyly); while the preassial polydactyly concerning the foot is known as tibial preassial polydactyly (or more briefly polydactyly tibial).
- Post-axial polydactyly . It is when the extra finger or fingers sprout from the side of the little finger of the hand or the smallest finger of the foot.
As in the previous case, there are two specific terms that refer to the post-axial polydactyly of the hand and foot; these are, respectively: post-axial ulnar polydactyly (or ulnar polydactyly) and fibular post-axial polydactyly (or fibular polydactyly).
- Central polydactyly . It is when the extra finger or fingers sprout between the central fingers of the hand (index, middle or ring finger) and of the feet (second finger, third finger or fourth finger).
Causes
To learn more: Polydactyly - Causes and Symptoms
Polydactyly is the result of mutations in the genes that control the correct development of the fingers and toes. Based on their experimental findings, the researchers believe that these genes are a fair number and that, among these, there are some that - if mutated - cause preassial polydactyly, others that cause post-axial polydactyly and others that determine central polydactyly.
According to the latest genetic studies, polydactyly would be associated with about 39 genetic mutations .
ISOLATED PHENOMENON OR SYNDROMIC PHENOMENON?
Polydactyly may be an isolated anomaly - where by isolation we mean that it is not associated with any particular morbid state - or it may be a clinical sign of a particular disease (usually a syndrome) of a genetic nature.
In the first case, it is a phenomenon that is not particularly relevant from the clinical point of view, as it is to be considered as having no dangerous consequences for the patient's health; in the second case, on the other hand, it is a phenomenon that is generally associated with other symptoms, some of which are also very serious.
In medical language, the isolated polydactyly takes the name of non-syndromic polydactyly, while the one associated with a particular morbid condition assumes the wording of syndromic polydactyla .
In these cases, the adjective "syndromic" means "which is part of a syndrome" or "which is related to a syndrome".
According to the most recent scientific researches, there would be at least 97 genetic-type syndromes characterized by one of the three types of polydactyly, described in the previous chapter.
Note: by syndrome we mean a complex of symptoms and signs, which characterize a specific clinical picture.
POLYDACTYLILY AS A FAMILY CONDITION
Polydactyly can be a recurring condition within the same family.
Faced with such cases, doctors speak of family polydactyly .
In general, family polydactyly is an isolated phenomenon, therefore a form of non-syndromic polydactyly.
Genetic characteristics of non-syndromic polydactyly and syndromic polydactyly
In general, non-syndromic polydactyly behaves like an autosomal dominant disease, while syndromic polydactyly is an autosomal recessive disease.
An autosomal dominant disease is a genetic condition in which, due to the realization of a specific clinical picture, the mutation of only one of the two alleles of the gene responsible for the pathology is sufficient; an autosomal recessive disease, on the other hand, is a genetic condition, in which, to observe a certain symptomatology, the mutation of both alleles of the gene guilty of the disease is necessary.
Symptoms and Complications
Syndromes that can cause polydactyly
Preassed polydactyly- Fanconi anemia
- Greig's Cephalopolisindactyly
- Townes-Brocks syndrome
- Holt-Oram syndrome
- Greig's Cephalopolisindactyly
- Down syndrome
- Meckel syndrome
- Bardet-Biedl syndrome
- Bardet-Biedl syndrome
- Meckel syndrome
- Pallister-Hall syndrome
- Holt-Oram syndrome
An individual with polydactyly can present abnormalities to one or both hands, as well as to one or both feet.
Generally, the extra finger or fingers are deprived of bones, tendons and joints; in other words, they only present the skin covering and the attached nail.
If they have bones and joints, they function like normal fingers; otherwise, they have no functional role.
POSTASSIAL POLYDACTYLLIA
Postaxial polydactyly is the most common type.
In most cases, the supernumerary finger or fingers are rudimentary, and therefore lacking in bony, tendinous and articular elements and provided only with the nail.
In general, post-axial polydactyly is a clinical sign of a syndrome sustained by genetic alterations of DNA.
Epidemiological data
Post-axial polydactyly is particularly widespread in the population of African origin.
In this regard, some statistical studies have shown that the incidence in Africans and African-Americans is equal to one case per 143 newborns, exactly 10 times higher than the incidence in individuals of Caucasian origin (one case every 1, 339 newborns) .
PREASSIAL POLIDACTYLIA
Preassial polydactyly is less common than postaxial type.
As in the previous case, the extra finger or fingers are generally devoid of bony, joint and tendon structures within them.
The preassial polydactyly is, very often, of syndromic character.
Epidemiological data
Preassial polydactyly affects one newborn every 3, 000 or so.
It is very common in the Indian population, so much so that, in this ethnic group, it represents the second most widespread anomaly in the hands.
CENTRAL POLIDATTILIA
Of the three types of polydactyly, the central one is the least common.
The supernumerary finger or fingers can tick:
- In the hand, between index and middle or between middle and ring finger.
- In the foot, between the second finger and the third finger or between the third finger and the fourth finger.
In general, central polydactyly is associated with syndactyly (ie when the fingers are joined together) and represents the clinical sign of a genetic syndrome.
In some cases, the extra finger or fingers sprout from the central fingers: in these situations, the usually most affected central finger is, in the hand, the index and, in the foot, the second finger.
Note: the second toe is the finger that follows the big toe. The third, fourth and fifth fingers are, of course, the successive ends on the second finger.
WHEN TO REFER TO THE DOCTOR?
Since polydactyly is often a clinical sign of a genetic disease, doctors advise parents of a child with this abnormality to consult a genetics expert for a specialist examination.
COMPLICATIONS
Polydactyly can represent an unsightly problem very much felt by carriers, so as to create serious problems and influence social relations.
Moreover, if it is particularly serious (the surplus fingers are at least two or are in particularly uncomfortable locations), patients may experience great difficulty in grasping the objects with their hands (if the anomaly were located here) or in finding shoes suitable for them (if the anomaly was borne by the feet).
Diagnosis
Physical examination is sufficient to diagnose polydactyly and its main characteristics.
In medicine, by physical examination we mean the evaluation by the doctor of the symptoms and signs present and / or reported by the patient.
To clarify whether the extra finger or fingers contain within them elements of a bony nature, the doctors resort to an X-ray examination .
As will be seen in the next chapter, clarifying the internal structure of supernumerary fingers is important for therapeutic purposes.
The physical examination also includes the evaluation of family history
In general, during the physical examination, the doctor asks the parents if any of their relatives are or were carriers of polydactyly. This investigation is important to understand whether the anomaly can be familiar or not.
GENETIC CONSULTING TO UNDERSTAND THE CAUSES
The polydactyly pruning people are generally subjected to a genetic test, aimed at the search for genetic mutations and chromosomal alterations.
Thanks to this test, doctors can determine the precise cause of polydactyly and whether it is syndromic or non-syndromic.
Treatment
If polydactyly is an aesthetic or functional problem (for example, it creates problems in grasping objects or finding a suitable pair of shoes), doctors can remove the finger or fingers in excess, using at least two different types of treatment :
- The binding of the extra finger e
- Surgical intervention.
Before describing what these two methods consist of, it should be pointed out that the choice of treatment to be adopted depends on the characteristics of polydactyly: the presence of bone, joint and tendon structures requires surgery; the absence of the aforementioned elements, on the other hand, means that a non-surgical remedy is sufficient.
EXTRA FINGER LIGATION
The ligation of supernumerary fingers consists in the application, by the doctor, of a sort of clip (or a lace) in the point of origin of the fingers themselves. This prevents the blood from reaching and keeping alive the skin tissue that constitutes the extra finger. Once the skin tissue is dead, its removal is simple and generally free of complications.So, in fact, with the technique of ligating extra fingers, doctors induce a process of dry gangrene .
Usually, for necrosis (ie death) of skin tissue, two weeks are required. During this time, the patient must wear a protective bandage.
The best age to carry out finger ligation is within the first 20 months of life.
Advantages: it is a minimally invasive technique, as it is not a surgical procedure.
Disadvantages: it is only applicable to patients with extra toes that do not have bony, joint or tendon elements.
SURGICAL REMOVAL
The surgery consists of: skin incisions, removal of the finger or supernumerary fingers (NB: removal includes the removal of bone, joint and tendon structures), possible reconstruction of part of the hand or foot (for example ligaments), closure of skin incisions and, finally, application of stitches and bandages.
There are several surgical approaches, each suitable for a specific type of polydactyly.
Furthermore, the severity of the anomaly also affects the choice of the most appropriate surgical technique.
As far as anesthesia is concerned, this can also be local; while as regards hospital stay, hospitalization is usually one day.
The best age to resort to surgery is around the year of life.
Advantages: surgery allows the removal of extra fingers made up of bones, joints and tendons, therefore fingers with a functional role.
Disadvantages: it is an invasive solution and, like any surgery, presents risks.
Prognosis
The treatments available at the present time make it possible to treat polydactyly with more than satisfactory results. The prognosis, therefore, is generally positive.
However, we must not forget that polydactyly is often a clinical sign of serious and untreatable conditions.
