What is Hypoplastic Thumb or Thumb Hypoplasia and What are its Classifications?

Hypoplastic Thumb which also is commonly called as Thumb Hypoplasia is a medical condition in which there is abnormal shortening or even in some cases total absence of the thumb when a child is born. This condition is usually present in one hand but in some cases both hands are equally affected. Hypoplastic Thumb or Thumb Hypoplasia has been classified into five categories based on the severity and abnormality of the thumb. These types are:

Hypoplastic Thumb or Thumb Hypoplasia

Type 1 Hypoplastic Thumb or Thumb Hypoplasia: In this type, the size of the thumb is just a little bit smaller than normal but this does not cause any dysfunction of the hand and the child is able to use the hand in a normal way without any difficulties.

Type 2 Hypoplastic Thumb or Thumb Hypoplasia: In this type, the thumb is much smaller in size. The muscles of the thumb are mildly underdeveloped and the joint is a little unstable. There is also tightness of the skin in the webspace between the index finger and the thumb. It may cause mild dysfunction of the hand and the child may have just a little bit of difficulty using the hand.

Type 3: In this type of Hypoplastic Thumb or Thumb Hypoplasia, the thumb is much smaller in size. There is significant underdevelopment of the muscles of the thumb and the thumb joints are very unstable. This makes it quite difficult for the child to use them normally.

Type 4: In this type of Hypoplastic Thumb or Thumb Hypoplasia, there is severe deformity in which the thumb is extremely small. There is almost no muscle present. The joints may also be absent and the thumb present virtually has no function and causes a lot of problem for the child in using the hand effectively in gripping or grasping objects. When you look at the thumb it looks as if there is a piece of skin hanging out from the hand near the index finger.

Type 5: This is the most severe type of Hypoplastic Thumb or Thumb Hypoplasia in which there is complete absence of the thumb. In such cases, the child finds it almost impossible to grip or grasp any object.

When it comes to the occurrence of Hypoplastic Thumb or Thumb Hypoplasia, it occurs in about 5% of children across the globe.

What is the Cause of Hypoplastic Thumb or Thumb Hypoplasia?

As of now, there is no known cause for Hypoplastic Thumb or Thumb Hypoplasia identified, although research is still ongoing as to find a cause for this condition. Some studies suggest that Hypoplastic Thumb or Thumb Hypoplasia occurs in the presence of certain other congenital conditions in which there is underdevelopment of the hands or forearm. Hypoplastic Thumb or Thumb Hypoplasia is seen mostly in children suffering from conditions like Holt-Oram syndrome or the Fanconi Syndrome.

What Happens to Children with Hypoplastic Thumb or Thumb Hypoplasia?

Hypoplastic Thumb or Thumb Hypoplasia is a visible deformity and based on the severity of the condition the child may find it difficult to use the hand normally. Some children learn to adapt to the missing finger and use the long and index finger for gripping objects even though they will have obvious problems with grasping objects.

How is Hypoplastic Thumb or Thumb Hypoplasia Diagnosed?

Hypoplastic Thumb or Thumb Hypoplasia is a visible deformity and is immediately observed as soon as the baby is born. Once Hypoplastic Thumb or Thumb Hypoplasia is observed, the physician will then conduct a detailed inspection to look for any other deformities that may be present along with Hypoplastic Thumb or Thumb Hypoplasia. The physician will also take an x-ray of the affected region to look at the internal structures of the hand.

How is Hypoplastic Thumb or Thumb Hypoplasia Treated?

Depending on the severity of the condition, children with hypoplastic thumb or thumb hypoplasia find it difficult with using the hands normally. Children with mild form usually Type 1 or Type 2 tend to be able to use their hands normally without any problems. One point here to note is that the ability of the child to hold or grab an object depends on the oppositional movement of the thumb. In milder forms of Hypoplastic Thumb or Thumb Hypoplasia, there is almost normal oppositional movement and hence the child does not have any problems with gripping or grasping. Children with the severe type of Hypoplastic Thumb or Thumb Hypoplasia which is the Type 3, 4, or complete absence of the thumb find it extremely tough to maneuver objects. In such cases, surgery is the treatment of choice to stabilize the joint such that some sort of oppositional movement can be created. In cases where there is complete absence of the thumb then surgery will be done to move the index finger to where the thumb should be so that the child is able to somewhat hold on to objects. This procedure is termed as pollicization. After this surgery, there is significant improvement in the child's ability to hold and maneuver objects in almost a normal fashion. A consultation with a plastic surgeon is the best way to go to find the best way to go about in extreme cases of Hypoplastic Thumb or Thumb Hypoplasia.

Written, Edited or Reviewed By:

, MD, FFARCSI

Last Modified On: May 3, 2016

Pain Assist Inc.

Pramod Kerkar
  Note: Information provided is not a substitute for physician, hospital or any form of medical care. Examination and Investigation is necessary for correct diagnosis.

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