Uneven Thumbs: All You Need to Know

What has actually happened to your thumb?

Why do you have uneven thumbs?

Did you smash it to the door or something?

Well, these will be the most common questions you may hear in your everyday life if you are a person with uneven thumbs. Why or how did you get these uneven thumbs?

Now, you can just tell everyone who asks about your uneven thumbs by sharing this piece of article which has everything people need to know about it.

It is often and most commonly called toe thumbs, clubbed thumbs, or short thumbs. It is type D brachydactyly which is an inherent condition in which all the fingers are normal but the end bones of the thumbs are shortened.

Let’s get into the details about uneven thumbs (Brachydactyly Type D) and get you familiar with all its aspects, some of which you knew already and some of which you had absolutely no idea about.

What is Brachydactyly?

Brachydactyly or uneven thumbs is a medical term which, in simple terms means, short finger(s). It is inherited mainly because of a dominant trait. The shortness of a finger is mainly relative to that of the length of the bones. It occurs as anomalies as a part of congenital syndromes. This can either be a genetic disorder or general symptoms.

But mainly it occurs due to isolated dysmelia (a disorder of limb). There are different types of brachydactyly depending on which bones are shortened. There is, however, no treatment needed for brachydactyly unless an accompanying disorder which uses hands and feet or produces symptoms.

In this article, you will learn everything in detail about uneven thumbs or Brachydactyly type D.

Types of Uneven Thumbs

There are several types of uneven thumbs, and it is categorized on the basis of which bones get affected. The types of brachydactyly are classified on the basis of anatomic grounds.

Type A-

Type A of brachydactyly (BDA) is the condition in which your middle phalanges are shortened. By middle phalanges, we mean the fingers that are second from the end of each digit. Type A of brachydactyly (BDA) is further classified by finger types, they are as follows-

1. Brachydactyly type A1 (BDA1)- In this type of brachydactyly, the middle phalanges of all digits are short and are often fused with terminal phalanges where the thumbs and toes are short of the proximal phalanges.

• It is a rare hand malformation that has no epidemiological studies reported yet.
• Type A1 of brachydactyly may be diagnosed with an anthropometric, clinical, and radiological evaluation of both your hands.
• The first human trait with the interpretation of Mendelian dominant inheritance was the hand deformity condition in type A1.
• This can be caused because of mutations in the Indian Hedgehog gene (IHH).

2. Brachydactyly Type A2- In Type A2 of brachydactyly, your index finger and sometimes your little finger is shortened. Individuals affected with this condition have triangular-shaped middle phalanx in the index fingers and the second toe.

• No epidemiology studies were conducted or reported and are a rare digital malformation.
• Clinical evaluation of hands and the index finger can be seen in X-rays.
• Research demonstrates autosomal dominant inheritance.

3. Brachydactyly Type A3- In Type A3 of brachydactyly, the middle phalanx of the little finger is shortened. Slanting of the distal articular surface of the middle phalanx leads to radial deflection of the distal phalanx, and the little finger is shortened.

• Brachydactyly type A3 condition is very common with a frequency of 21% among Japanese school children.
• This type A3 is autosomal dominant with reduced penetrance.
• No gene or locus for Brachydactyly Type D (BDA3) has yet been identified.

Type B

Type B of brachydactyly (BDB) is when there is an absence of the terminal parts of the index with a complete absence of fingernails. The thumbs are always intact but they frequently show flattening, splitting, or duplication of the distal phalanges.

• This is a rare hand malformation with only a few published reports.
• Clinical and radiological examinations are conducted.
• It is autosomal dominant inheritance and variable expressivity.

Type C

Type C of brachydactyly (BDC) is very rare with affecting the index, middle, and little fingers. The middle phalanges are shortened but the ring finger is the longest of all.

• This type is rare with only a few reported pedigrees.
• Clinical evaluation and X-rays of hands pattern profile analysis are done.
• Many studies support an autosomal dominant trait.

Type D of brachydactyly is talked about in detail below.

What is Brachydactyly Type D (uneven thumbs)?

Brachydactyly Type D is a clinical condition recognized by a thumb being comparatively round and short with accompanying a wide nail bed. It is a human autosomal dominant condition associated with the HOXD13 gene, in which the thumbs are short.

Homeobox protein Hox-D13 is a protein encoded by the HOXD13 gene that is present in humans, and belongs to the homeobox family of genes.

Some other names of brachydactyly are uneven thumb, hammer thumb, stubbed thumb, short thumb, potter’s thumb, clubbed thumb, royal thumb, club thumb, murderer’s thumb, toe thumb, and stub thumb.

Causes of Brachydactyly

“Why do I have uneven thumbs or toes?” – ever wondered this? Well, let us tell you the actual causes of why do you have brachydactyly.

Brachydactyly can be caused mainly because of few reasons which are mentioned below:-

• This condition is inherited which makes genetics the main cause. If you have uneven or shortened thumbs, then it is very much likely that one of your family members also has/had the same condition.
• There is a misconception among people that, two different mutations in a gene contribute to this condition. But in reality, you can inherit this condition if only one of your parents possesses the gene of brachydactyly type D. This condition is known as an autosomal dominant condition.
• In very rare cases, it is possible that you can get affected with brachydactyly if you were exposed to medications that a mother might took during pregnancy.
• It can also be caused because of the blood flow problems to your feet or hands, specifically in growing babies.
• It is also possible that your brachydactyly of any type is symptomatic of a genetic syndrome. This case is much rarer. If so, you will have other symptoms besides uneven thumbs or toes.
• Brachydactyly might be caused to someone who is already going through Cushing’s syndrome or Down syndrome.

Symptoms of Brachydactyly Type D

The symptoms may vary from person to person. The signs of having the condition of uneven thumbs or type D brachydactyly is usually during birth but with passing years, there is a possibility that the shortened thumbs become obvious.

• The most common symptoms of brachydactyly are shorter fingers, thumbs, or toes than normal.
• The main symptom of type D brachydactyly is uneven thumbs which are usually shorter than the usual size. With shortened and uneven thumbs, you may face difficulty with taking a grip (especially if you play any musical instrument).
• The medical phrase of the symptom of uneven thumbs is “short distal phalanx of the thumb” and in simple terms, it’s called short outermost bone of the thumb. This information is taken from Human Phenotype Ontology (HPO) which collects data on symptoms of medical resources from its description.

Clinical description of uneven thumbs (Brachydactyly type D)

The distal phalanx of the thumb(s) alone is shortened. The two degrees of thumb shortening are either unilaterally or bilaterally. It is to be taken into consideration that the base of the distal phalanx is much broader than the surface of the proximal phalanx from where it articulates. The distal end of the bone shows hyperplasia. Other research and studies established that the shortened distal phalanx is a result of the early closure of epiphyses.

Physiology of Uneven Thumbs

Brachydactyly Type D is a premature or partial fusion closing of the rounded end of a long bone at the adjacent joints of the thumb. This condition may be unilateral or bilateral. It means either affecting both the thumbs or affecting only one thumb.

In 1923, J.K. Breithenbecher found that the distal phalanges (digital bones) of uneven or stubbed thumbs were one-half the length of full-length thumbs, while in 1957, R.M. Stecher claimed that it is approximately two-thirds of the full-length thumb.

Genetics of Uneven Thumbs

A study of genetics trait exhibits that uneven thumbs or brachydactyly type D is autosomal recessive in the phenomenon of one variant of a gene. This condition is usually associated with the HOXD13 gene which as a result is central in the formation and growth of toes and fingers present in many vertebrates. It is also independent of the commonly inherited hereditary trait. No specific gene for uneven thumbs or brachydactyly type D has been identified yet.

The hereditary trait of Uneven Thumbs

A scientific study conducted in Israel in the year 1965 found that 3.05% of the Palestinians living in Israel had unilateral or bilateral thumbs. Uneven thumbs or stubbed thumbs are relatively common in Japan. Eastern Nepal has also found cases of uneven thumbs in Jirel ethnic individuals from participation in several epidemiologic research and studies.

Several studies were also conducted which included taking radiographs of wrists and hands to study and examine their skeletal structure. Of the researched and studied sample, 3.55% individuals of 2130 participants were found to have uneven thumbs (brachydactyly type D).

Terminology of Uneven Thumbs

Brachydactyly Type D is unknown under numerous names. The most commonly used names are uneven thumbs or clubbed thumbs.

R.A. Hefner, an American researcher termed it as “short thumb” in the year 1924 and it continued to be used in further studies and researches.

However, people today often tend to use the term “uneven thumbs” which is a clinical condition associated with several diseases.

Diagnosis of Uneven Thumbs

Radiographs, clinical evaluation, and anthropometric are the diagnosis of uneven thumbs. It shows a broad, short, or uneven distal phalanx of thumbs which can either be unilateral or bilateral.

The nature of genetic counseling depends both on the pattern of inheritance of the type of brachydactyly present in the family and on the presence or absence of accompanying symptoms.

Prenatal diagnosis is usually not indicated for isolated forms of brachydactyly, but it may be appropriate in some syndromic forms.

Inheritance of Uneven Thumbs

Uneven thumbs or the shortness of thumbs is described as a trait that is autosomal recessive. Other research and studies also confirmed the autosomal recessive pattern with reduced penetrance.

Epidemiology of Uneven Thumbs

Type D of brachydactyly or uneven thumbs is common. The prevalence of this often varies from 0.41% to 4.0%. Its high prevalence is found in the Japanese and Israeli Arabs population.

According to Online Mendelian Inheritance in Man 232 entries were provided after using the term brachydactyly. The various types of isolated brachydactyly are very rare, except for types D and A3, which are most common, prevailing with 2%.

Treatment of Uneven Thumbs

There is no specific treatment or management that applies to all types of brachydactyly. The prognosis for the brachydactyly is mainly dependent on the nature of the brachydactyly, or it may vary from good to severely influencing hand function. If brachydactyly forms part of a syndromic entity, prognosis often depends on the nature of the associated anomalies.

If the brachydactyly type D or uneven thumbs condition has hand functions or any cosmetic reasons, then plastic surgery is indicated but that may not be typically needed.

In very rare or severe cases, surgery can be used to treat your uneven thumbs condition.

Surgery may include cutting your bone (osteotomy) which leads to gradual lengthening of your shortened fingers (thumbs).

Typically, no treatment is required unless your condition is a part of another syndrome. You should have no medical concerns as such related to your thumbs or feet.

Risks of uneven thumbs

Brachydactyly or you can call it ‘uneven thumbs’ in simpler terms, is an inherited condition. If one of your family members is suffering from this condition, then the chances of you having it are much higher. There are some people who may have a higher risk to get brachydactyly.

• Women are more likely to have brachydactyly type D than men. This is because partially women have more chances to experience the full expression of a trait than men and it is also more noticeable.
• If your family has someone with type D brachydactyly (uneven thumbs) then, the chances of you getting it too is higher.
• The chances of brachydactyly type D are higher if a child is born with Down syndrome.

Complications

• There are no significant complications for most people who have this condition of uneven thumbs, that hinder their daily lives.
• But in some cases, if the condition is severe enough then the person faces some difficulty in walking or a limit to the functioning of their hand. You do not need to stress out, physical therapy and surgery can be used to improve the condition.

Impact of Brachydactyly on Your Health

Brachydactyly rarely has any effect on your overall health. In only extreme cases, brachydactyly makes it difficult for you to perform certain tasks. If you face any health impacts it is only because brachydactyly is combined with another health condition. Healthcare professionals can examine and identify the cause of why brachydactyly is connected to any other syndrome. If young children have brachydactyly condition then doctors can identify it with Cushing’s syndrome, and it does not affect your child’s health but is only a symptom of another condition.

How to Prevent Brachydactyly from Affecting your Health

You can prevent brachydactyly from affecting your health by taking into consideration, some effective measures. In severe cases of brachydactyly, the doctor can recommend you to take physical therapy. This case is, however, rare but it will improve the range of strength, motion, and functionality in your affected areas if your ability to hold objects or walk is disturbed.

Most of the people with brachydactyly (uneven thumbs) condition live completely normal lives and they do not feel self-conscious about it.

But there are some people who may feel self-conscious or doubt themselves about the appearance of their hands, thumbs or feet, but are otherwise, healthy.

And, if you are one of them, then you need to understand that you should accept yourself as who you are because every human has some flaws or the other but that does not mean they are imperfect. If Brachydactyly of any type (A, B, C, D, etc) is somehow connected to another syndrome, then the outlook will vary depending on the situation of the individual.

By now, you must have got a lot of knowledge about uneven thumbs which is a type D of Brachydactyly which is a very common condition. I hope you have found the article helpful enough!