Die Achondrogenesie : klinische, radiologische und morphologische Untersuchungen
The achondrogenesis in its subgroupes type IA, IB and II marks one of the most severe osteochondrodystrophies, always causing death prenatal or perinatal. This thesis delivers a review about most and the most important contributions to the literature about achondrogenesis. Following this, detailed examinations of own cases with achondro-genesis type II are presented. The main interest in the examinations 1. have been laid on the way the collagen type II gets exchanged mainly into collagen type I in the epiphysal cartilage tissue, 2. the way of ossification in the bones while enchondral ossification is disordered, and 3. the actual way of bone growth in achondrogenesis. Statements are also made regarding other peculiarities of the achondrogenesis type II, as there are polyhydramnion, premature birth, stillbirth, respiratory insufficiency, bent bones or others, described in the literature, but not yet clearly causal. During own examinations three cases with achondrogenesis type II of the 17th, 31th and 34th week of gestation were looked at. The infants had been examined in six steps regarding 1. physical, 2. radiological, 3. visceral, 4. anatomical and histological development in 5. general and 6. detailed view. This approach made it possible to compare physical, radiological and anatomical results with histological results. Genetic mutations in COL2A1, the gene for collagen type II, lead to defective and missing collagen type II, which causes a failure in the mechanical strain of the modified epiphysal cartilage tissue in the articulations. This way, forces on the joints also affect the non-cartilage tissues, mainly by stimulating the fibrocytes in the paravascular tissue, causing increase and dilatation of the fibrovascular structures in the achondrogenesis type II. The production of this substituting tissue leads to all that special attributes of the epiphysal cartilage in achondro-genesis type II. It also generates different forms of ossification at the metaphysis and even in the epiphysis. Similarly, growth of the periostal bone is substitutively stimulated and causes growth of the entire bone, normally occurring enchondral. The mechanical forces on the joints influence the remarkable threefold-layered periostal rings around the border of the metaphysis, which definitely are wider and higher in the achondrogenesis than normally. At the outside is a layer in continuation of the clear wider periost. The middle layer shows numerous cells and corresponds to the cambium below the periost. The osseous part of the ring borders the metaphysis. The outside and the top of the osseous ring is covered by osteocytes, generating irregular growth of the entire bone in length and width. External forces like traction and compression, acting differently on the rings around the metaphyses via joints and periost, also cause the bending of bones. This in turn is responsible for the secondary periostal proliferation, causing a deposition of osteoid on the statically delicate bones.
info:eu-repo/classification/ddc/610, Medizin, Achondrogenesis, Chondrodystrophie, Kollagen Typ 2-Gen-Mutation, collagen type 2 mutation
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