Generality
Polydactyly is a "congenital physical anomaly, characterized by the presence, in the hands or feet (or both), of more than 5 fingers.
There are at least 3 types of polydactyly:
- preaxial polydactyly, in which the supernumerary toe (s) emerge from the part of the thumb / big toe;
- postaxial polydactyly, in which the supernumerary toe (s) emerge from the part of the little finger / fifth toe;
- finally, the central polydactyly, in which the supernumerary finger or fingers emerge from the central fingers of the hand or foot.
There are various treatments: the choice of the most suitable one depends on the characteristics of the additional fingers and on the evaluations of the doctor in the diagnostic field.
Review 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. Human cells contain, in their nucleus, 23 pairs of homologous chromosomes (22 of the autosomal non-sexual type and one pair of the 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, or biological molecules fundamental for life, derive. In the genes, there is "written" part of who we are and who we will become.
Each gene is present in two versions, the alleles: one allele is of maternal origin, therefore 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 more than 5 fingers.
Thus, an individual with polydactyly is a person who has 6 or more fingers in their hands and / or feet.
Doctors refer to "extra fingers" using the terms: extra finger (or fingers), supernumerary (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 ".
Hence, the literal meaning of polydactyly is "many fingers".
SYNONYMS OF POLYDACTILY
Two synonyms of polydactyly, very little used, are: hyperdactyly ("hyper-" is a prefix that indicates overabundance) and polydactyly.
IT IS THE CONTRARY OF OLIGODATTILIA
Polydactyly is the condition contrary to oligodactyly, which consists in the presence of fewer than 5 fingers and / or feet.
The prefix "oligo-" comes from the Greek word "oligos" (ὀλίγος ‚), which means" little ".
TYPES OF POLYDACTYLY
Doctors considered it appropriate to classify polydactyly into three different types, depending on where the surplus finger or fingers reside.
These three types are called:
- Preaxial polydactyly. It occurs when the extra finger or toes protrude from the thumb (in the hand) or the big toe (in the foot).
In this case, the preaxial polydactyly affecting the hand takes the name of radial preaxial polydactyly (or more simply radial polydactyly); while the preaxial polydactyly concerning the foot is known as tibial preaxial polydactyly (or more briefly tibial polydactyly). - Postaxial polydactyly. It is when the extra finger or toes poke out of the little toe part of the hand or the smallest toe 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: ulnar postaxial polydactyly (or ulnar polydactyly) and fibular postaxial polydactyly (or fibular polydactyly). - Central polydactyly. It is when the extra finger or fingers sprout between the middle fingers of the hand (index, middle or ring finger) and toes (second finger, third finger or fourth finger).
Causes
For further information: Polydactyly - Causes and Symptoms
Polydactyly is the result of mutations in the genes that control the proper development of the fingers and toes. Based on their experimental findings, the researchers believe that the aforementioned genes are a fair number and that, among them, there are some that - if mutated - cause preaxial polydactyly, others that cause postexial polydactyly and still others that cause central polydactyly.
According to the latest genetic studies, polydactyly is associated with about 39 genetic mutations.
ISOLATED PHENOMENON OR SYNDROMIC PHENOMENON?
Polydactyly can be an "isolated anomaly - where isolated s" means that it is not associated with any particular disease state - or it can 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 a clinical point of view, as it is to be considered without dangerous consequences for the patient's health; in the second case, however, it is a phenomenon that tends to be associated with other symptoms, some of which are also very serious.
In medical language, isolated polydactyly is called non-syndromic polydactyly, while that associated with a particular morbid condition takes the name of syndromic polydactyly.
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 research, there are at least 97 genetic syndromes characterized by one of the three types of polydactyly, described in the previous chapter.
Please note: by syndrome s "means a complex of symptoms and signs, which characterize a specific clinical picture.
POLYDACTILY AS A FAMILY CONDITION
Polydactyly can be a recurring condition within the same family.
Faced with such cases, doctors speak of familial polydactyly.
Generally, familial polydactyly is an isolated phenomenon, hence a non-syndromic form of polydactyly.
Genetic characteristics of non-syndromic polydactyly and syndromic polydactyly
Generally speaking, non-syndromic polydactyly behaves like an autosomal dominant disease, while syndromic polydactyly behaves like an autosomal recessive disease.
An autosomal dominant disease is a genetic condition in which, for a specific clinical picture to materialize, the mutation of only one of the two alleles of the gene responsible for the disease is sufficient; an autosomal recessive disease, on the other hand, is a genetic condition in which, in order to observe a certain symptomatology, it is necessary to mutate both alleles of the gene responsible for the disease.
Symptoms and Complications
Syndromes that can cause polydactyly
Preaxial polydactyly- Fanconi anemia
- Greig's cephalopolysyndactyly
- Townes-Brocks syndrome
- Holt-Oram syndrome
- Greig's cephalopolysyndactyly
- Down syndrome
- Meckel's syndrome
- Bardet-Biedl syndrome
- Bardet-Biedl syndrome
- Meckel's syndrome
- Pallister-Hall syndrome
- Holt-Oram syndrome
An individual with polydactyly may have abnormalities in one or both hands, as well as in one or both feet.
Typically, the extra finger or fingers have no bones, tendons, and joints on the inside; in other words, they have only the skin covering and the attached nail.
If they have bones and joints, they function like normal fingers; otherwise, they have no functional role.
POSTAXIAL POLYDACTYLY
Postaxial polydactyly is the most common type.
In most cases, the supernumerary finger or fingers are rudimentary, therefore without bone, tendon and joint elements inside and provided only with the nail.
Generally, postexial polydactyly is a clinical sign of a syndrome sustained by genetic DNA alterations.
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 Afro-Americans is equal to one case every 143 new borns, exactly 10 times higher than the incidence in individuals of Caucasian origin (one case every 1,339 new borns). .
PREAXIAL POLYDACTYLY
Preaxial polydactyly is less common than the postaxial type.
As in the previous case, the extra finger or fingers generally lack bone, joint and tendon structures within them.
Preaxial polydactyly is very often syndromic.
Epidemiological data
Preaxial polydactyly affects approximately one in 3,000 newborns.
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 POLYDACTILY
Of the three types of polydactyly, the central one is the least common.
The extra finger or fingers may stick out:
- In the hand, between index and middle finger or between middle and ring finger.
- In the foot, between the second and third toes or between the third and fourth toes.
Typically, central polydactyly is associated with syndactyly (i.e. when the fingers are joined together) and is the clinical sign of a genetic syndrome.
In some cases, the extra finger or toes protrude from the middle fingers: in these situations, the middle finger usually most affected is the index finger in the hand and the second finger in the foot.
Please note: the second toe is the toe that follows the big toe. The third, fourth and fifth toes are, of course, the extremities following the second toe.
WHEN TO SEE THE DOCTOR?
Since polydactyly is often a clinical sign of a genetic disease, doctors recommend that parents of a child with the aforementioned abnormality consult a genetic expert for a specialist examination.
COMPLICATIONS
Polydactyly can represent an unsightly problem much felt by carriers, so much so as to create serious inconvenience and influence social relationships.
Furthermore, if it is particularly serious (the extra fingers are at least two or are in particularly uncomfortable locations), patients may have great difficulty in grasping objects with their hands (if the anomaly was located here) or in finding shoes. suitable for them (if the anomaly is in the feet).
Diagnosis
To diagnose polydactyly and its main features, a physical examination is sufficient.
In medicine, physical examination means the physician's evaluation of the symptoms and signs present and / or reported by the patient.
To clarify whether the extra finger or fingers contain elements of a bony nature within them, 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.
Physical examination also includes assessment of family history
Generally, during the physical examination, the doctor asks the parents if any of their relatives is or was a carrier of polydactyly. This investigation is important to understand if the anomaly may be familial or not.
GENETIC CONSULTING TO UNDERSTAND THE CAUSES
People pruners of polydactyly are usually subjected to a genetic test, aimed at looking for genetic mutations and chromosomal alterations.
With this test, doctors can determine the precise cause of polydactyly and whether it is syndromic or non-syndromic.
Treatment
If polydactyly represents an aesthetic or functional problem (for example, it creates problems in "grasping objects or finding a suitable pair of shoes), doctors can remove the extra finger or toes, using at least two different types of treatment. :
- The extra finger ligation e
- The surgery.
Before describing what these two methods consist of, it should be noted that the choice of treatment to be adopted depends on the characteristics of the polydactyly: the presence of bone, joint and tendon structures requires surgery; the absence of the aforesaid elements, on the other hand, means that a non-surgical remedy is sufficient.
EXTRA FINGER BINDING
The tying of the surplus fingers consists in the application, by the doctor, of a sort of clip (or a lace) at the point of origin of the fingers themselves. This prevents blood from reaching and keeping alive the skin tissue that makes up the extra finger. Once the skin tissue has died, its removal is simple and generally uncomplicated.So, in fact, with the extra finger ligation technique, doctors induce a dry gangrene process.
Usually, two weeks are required for necrosis (i.e. death) of the skin tissue. Throughout this time, the patient must wear a protective bandage.
The best age for finger tying is within the first 20 months of life.
Benefits: it is a minimally invasive technique, as it is not a surgical procedure.
Disadvantages: it is applicable only to patients with extra fingers without bone elements, joints and tendons inside them.
SURGICAL REMOVAL
The surgery consists of: skin incisions, removal of the finger or supernumerary fingers (NB: the removal includes the removal of bone, joint and tendon structures), possible reconstruction of part of the hand or foot (for example the ligaments) , closing of skin incisions and, finally, applying sutures and bandaging.
There are several surgical approaches, each suitable for a certain 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 of a local type, while as regards the stay in hospital, hospitalization is usually one day.
The best age to have surgery is around the year of life.
Benefits: 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, it presents risks.
Prognosis
The treatments available at the present time allow you to cure polydactyly with more than satisfactory results. The prognosis, therefore, is generally positive.
However, it should not be forgotten that polydactyly is often a clinical sign of serious and untreatable conditions.
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