Madelung: It was Otto Madelung who first described fork-shaped bowing the wrists. That’s why this fork-shape in the wrists is called Madelung Deformity or Madelung for short
You can have only Madelung, however most of the times this won’t be hereditary and will occur only in one of the wrists. If you have Madelung in both wrists the chance that you have Leri Weill or another disorder (like Turner for example) is high
The deformity in the wrists with Madelung works in the same way as the disturbed growth in the legs in Leri Weill patients so I will try to explain both at the same time.
Leri Weill or Dyschondrosteosis:
The scientists Leri and Weill have first described the bone dysplasia (or growth disorder) Dyschondrosteosis. The word Dyschondrosteosis seems a difficult word or name, however it is Latin for bad cartilage.
This name fits perfectly, because it is the cartilage within the patients that causes the problems. What happens exactly?? It all happens in the growth plates. Growth plates ensure growth during your youth. In case of Leri Weill (and Madelung) there is something wrong in the growth plates of the stretched bones.
What are stretched bones?: the bones in your arms and legs. So these are you femur (in your upperleg), your tibia & fibula (in your lowerleg), your humerus (in your upperarm) and your ulna and radius (in your lowerarm).
What is wrong with these growth plates? In your growth plates there are bone cells (chrondrocytes) that enable growth in length. These chrondrocytes are neatly arranged in rows, all rows next to each other. In Leri Weill and/or Madelung patients a certain part of these chrondrocytes are NOT neatly arranged in rows, instead they are not arranged at all! (chaos!) The chaotic growing chrondrocytes do not result in length-growth and therefore the bone will not get the length it was suppose to get.
That in itself is not the biggest problem. For example, most patients will not have any problems with there upper arms and upper legs. In those limbs there is only one bone and if it’s somewhat smaller or larger is not dependent on its function. The only thing you’ll notice is shorter/longer limbs compared to the rest of your body. This will not cause too much problems, except for remarks or difficulties in buying clothes. However, it will not cause any pain.
The real problem is caused by the fact that each growth plate has a different amount of chaotic chrondrocytes (bone cells). For example, one growth plate has 10% chaotic bone cells, the next has 25% and the one after that has 33%. Of course you can get an arm or leg length difference. However, most people have a length difference between arms and/or between legs. This will only cause problems when the difference is too large. The biggest affect of these length differences can be seen within your lower arms and lower legs.
What happens in your lower arms and lower legs? Like I said, you have two bones in your lower arms and lower legs. These two bones have to fit neatly on to each other to make a good connection with (in case of your lower arms) your hand and elbow (and in case of your lower leg: foot and knee). Your ulna and radius have to form some kind of plateau (supporting line) at the site of your hand. On this, your wrist bones rest and are able to form your wrist.
You can imagine that when the two bones do not grow side by side (to reach the same length at the wrist-side) than this will cause a bone disorder. This disorder in the wrists is called Madelung and there are three kinds of Madelung. I will put them here in science language. I have tried to contact the scientist, but still no answer. If someone really understands the definitions below, please contact me.
- Classic Madelung deformity. Dorsal subluxation of the distal ulna resulting in a "dinner fork" deformity of the wrist
- Reverse Madelung deformity. Volar subluxation of the distal ulna
- Chevron carpus. Maintenance of the alignment of the wrist, resulting in impingement of the lunate bone on the distal radius, the most painful variant
In a later stadium I will try to post some pictures beside this text.
Cause: SHOX!
In about 70% of the patients DNA tests will find a mutation in the SHOX gene. SHOX stands for Short Stature Homeobox. This is a big word, but all it says is that the SHOX gene is some kind of manager of other genes in order to form a symmetric skeleton. It is especially important in growth and in the maturation (sort of becoming an adult) of the bones in arms and legs.
The SHOX gene is on the X-chromosome and on the Y-chromosome. Okay, so what are chromosomes?? A human being has 46 chromosomes (unless they have a chromosome disorder, but that’s a different story), which consists of 23 sets of 2 chromosomes. From each set one is obtained from your dad and one came from your mom. 44 Chromosomes (so 22 pairs) are called autosomes and one pair either consists of 2 X chromosomes (when you’re a female) of an X and a Y (when you’re a male).
The Y chromosome differs a lot from the X chromosome, e.g. it is much smaller. However there are some parts on the Y chromosome that are also on the X chromosome. These parts are called Pseudoautosomal Regions. In other words, parts that behave like autosomes (so no difference between male and female). Because the SHOX gene is in such a region, there should be no difference between males and females with for example Leri Weill. However, there is a difference between male and female patients with Leri Weill. They do not know the exact cause yet, but for example female hormones might play a role. On the other hand testosterone (male hormone) might counteract with Leri Weill and therefore Leri Weill might be less severe in males. We'll have to wait what science will teach us on this.
SHOX is not only active in the bones, but also in the muscles. That’s why scientists (and also myself) are very interested to hear if some of you are having yet unexplainable muscle problems. For example, some patients have really massive muscles (without training them a lot), or suffer from muscles that show spasms after surgery (and the time after).
Okay, let me know if I have to explain more or differently.
Best Wishes, Paula
