These cells play an important role in the development of the craniofacial appearance, and loss of one copy of treacle affects the cells ability to form the bones and tissues of the face. Other mutations
POLR1C and POLR1D mutations are responsible for a minority of cases of Treacher Collins. POLR1C is found on chromosome 6 at position 6q21.2 and POLR1D is found on chromosome 13 at position 13q12.2. Those genes code for a protein subunits shared between RNA polymerase I and III. Both of these polymerases are important for ribosome biogenesis. Diagnosis
Genetic counseling
TCS is inherited in an autosomal dominant manner and the penetrance of the affected gene is almost complete. Some recent investigations, though, described some rare cases in which the penetrance in TCS was not complete. Causes may be a variable expressivity, an incomplete penetrance or germline mosaicism. Only 40% of the mutations are inherited. The remaining 60% are a result of a de novo mutation, where a child has a new mutation in the responsible gene and did not inherit it from either parent. In the outcome of the disease, inter- and intrafamilial variability occurs. This suggests that when an affected child is born, it is important to investigate the parents to determine whether the affected gene is present, because the parent could have a mild form of the disease that has not been diagnosed. In this case, the risk of having another affected child is 50%. If the parents do not have the affected gene, the recurrence risk appears to be low.
Léri–Weill dyschondrosteosis or LWD is a rare pseudoautosomal dominant genetic disorder which results in dwarfism with short forearms and legs (mesomelic dwarfism) and a bayonet-like deformity of the forearms (Madelungs deformity). Causes
It is caused by mutations in the short-stature homeobox gene found in the pseudoautosomal region PAR1 of the X and Y chromosomes, at band Xp22.33 or Yp11.32.SHOX gene deletions have been identified as the major cause of Leri–Weill syndrome.Leri–Weill dyschondrosteosis is characterized by mesomelic short stature, with bowing of the radius more so than the ulna in the forearms and bowing of the tibia while sparing the fibula. Diagnosis
Diagnosis is made following genetic blood testing. Treatment
History
LWD was first described in 1929 by André Léri and Jean A. Weill. References


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