What is Mesomelic Dysplasia?
Dysplasia is often referred to as abnormal growth, differentiation, and maturation. Mesomelic Dysplasia which is also known as Langer Mesomelic dysplasia is a disorder related to Bone growth. The individuals suffering from Mesomelic dysplasia suffers from shortening of the limb bones from the middle disproportionately. So usually, the patients are Short (Dwarf). Two bones of the body named as Ulna of forearm and Fibula of the Lower leg are not efficiently developed or absent, while other bones like radius(forearm) and tibia(lower leg) are generally short, curved and unusually thick. An impairment of forearm and wrist bones which is referred to as Madelung deformity (Rare Hereditary Disorder) usually cause pain and restricts the wrist actions. Also, people often have underdeveloped Mandible (Lower Jaw Bone). It is a rare disorder.
Causes of Mesomelic Dysplasia
Changes associated with Shox gene which is also known as Transcription Factor is responsible for Mesomelic Dysplasia. Shox gene is involved in instructing other genes to regulate certain functions. The particular type of protein synthesized by the Shox gene is responsible for the growth and development of bones. The general cause of Mesomelic Dysplasia is the deletion of the whole gene. Other change that contributes to the disorder is mutations in a gene. Changes due to all these factors greatly affect the synthesis of a particular protein. Deficiency of protein obstructs the usual growth and developments of bones. Later, patients also suffer from various skeletal disorders.
Shox Gene (Major Gene) of Mesomelic Dysplasia
The Shox gene is a part of the Home box genes (Large Family). It acts during early rudimentary development to support the growth of body parts. Shox gene is commonly involved in the development of the skeleton and performs a key role in growth, differentiation, and bone maturation.
Copy of Shox gene is located on each chromosome (X and Y chromosomes). So, each individual whether it is a man or women has two of the Shox gene. Shox gene can be known by several names like PHOG, Growth control factor, X-linked.
Types of Mesomelic Dysplasia
Mesomelic Dysplasia can be categorized into 6 categories:
Langer Kind is marked by mental impairment, underdeveloped growth of the mandible, the bones of the forearm and lower leg. It is an Autosomal recessive disorder type.
Nievergelt Kind is the most severe type among all. Thickening of radius and ulna is some of the characteristics. A most common symptom is Club Foot. It is an Autosomal dominant disorder.
- Reinhardt Kind is commonly marked by dwarfism, pain and restricted movements of the wrist. It is an Autosomal dominant type.
- Robinow kind is more associated with problems of spine and ribs. Osteosclerosis is also commonly found. The span and symptoms vary from person to person. It is also associated with genital infections and is an Autosomal dominant type.
- Werner kind in which absence of thumb is generally seen. Congenital heart disease is also commonly seen in Werner kind. It is an Autosomal dominant type.
- Lamy-Bienenfeld kind is generally marked by the absence of radius, ulna and Humerus bones, Fingers and toes are found to be abnormal. It is an Autosomal dominant type.
- Autosomal Dominant Inheritance Pattern of Mesomelic Dysplasia
- Mesomelic Dysplasia is marked in a male or female when the alleles are present in heterozygous condition. It is not restricted to sex only. It also means that some people have more severe symptoms than others.
- Attribute of Inheritance Pattern of Mesomelic Dysplasia
- Generation after generation is affected.
During conception, each child has 50% probability to inherit the condition. Gender of the children is purely not associated with the inheritance pattern.
Diseases Associated with Mesomelic Dysplasia
- Madelung deformity
- Skeletal Dysplasia
Clinical Signs and Symptoms of Mesomelic Dysplasia
Few symptoms are very frequent in Mesomelic Dysplasia.
- Deformity of the Ulna.
- Madelung Deformity.
- Shortening of the limb.
- Restrict movements in the wrists and severe pain.
Diagnosis of Mesomelic Dysplasia
Test to collect all the information regarding changes in genes, proteins or chromosomes patterns. Results of genetic testing confirm all the possibilities of disorder to happen. It gives a clear picture of the genetic condition of the entire body.
Methods Used in Genetic Testing:
- Gene tests which are also known as Molecular genetic tests is the study of a specific gene or the mutations occur in DNA fragments that lead to disability in a genes pattern.
- Chromosomal genetic tests which are done for confirming other disorder like aneuploidy or polyploidy.
- Biochemical genetic tests account for the study of proteins.
- Genetic testing is useful and has side effects at the same time. With the help of a counselor, one can decide to have genetic testing discussing all the aspects.
Some of the Diagnostic Therapies:
- Molecular Diagnosis of Mesomeric Dysplasia
- Molecular Diagnosis of Mesomeric Dwarfism
Genetic Disorders like Mesomelic Dysplasia are associated with the changes in the gene, chromosome patterns, and deficiencies in some particular proteins. It is generally an Autosomal Dominant Disorder which is inherited in the next generations. Children of next generation can be affected if a gene is present in heterozygous condition. The disorder is often marked by disabilities in growth, development, and maturation of bones. Therapies are available as treatment. People suffering from Mesomelic Dysplasia generally are of low stature. There is no life threat in Mesomelic Dysplasia and one can involve in diagnosis without stress.
- Ambrosetti, F., Palicelli, A., Bulfamante, G., & Rivasi, F. Langer Mesomelic Dysplasia in Early Fetuses: Two Cases and a Literature Review. Fetal And Pediatric Pathology, (2013). 71-83. doi: 10.3109/15513815.2013.807322
- Zinn, A., Wei, F., Zhang, L., Elder, F., Scott, C., Marttila, P., & Ross, J. CompleteSHOX deficiency causes Langer mesomelic dysplasia. American Journal Of Medical Genetics, (2002). 158-163. doi: 10.1002/ajmg.10422