Replacements of glycine with serine or cysteine are seen less often in fatal type II OI, while replacements with valine, aspartic acid, glutamic acid, or arginine are seen more often.At a larger scale, the relationship between the collagen fibrils and hydroxyapatite crystals to form bone is altered, causing brittleness. Bone fractures occur because the stress state within collagen fibrils is altered at the locations of mutations, where locally larger shear forces lead to rapid failure of fibrils even at moderate loads because the homogeneous stress state normally found in healthy collagen fibrils is lost. OI is therefore a multi-scale phenomenon, where defects at the smallest levels of tissues (genetic, nano, micro) domino to affect the macro level of tissues. Diagnosis
Diagnosis is typically based on medical imaging, including plain X-rays, and symptoms. In severe OI, signs on medical imaging include abnormalities in all extremities and in the spine. As X-rays are often insensitive to the comparatively smaller bone density loss associated with type I OI, DEXA scans may be needed. : 1514 An OI diagnosis can be confirmed through DNA or collagen protein analysis, but in many cases, the occurrence of bone fractures with little trauma and the presence of other clinical features such as blue sclerae are sufficient for a diagnosis. A skin biopsy can be performed to determine the structure and quantity of type I collagen. While DNA testing can confirm the diagnosis, it cannot absolutely exclude it because not all mutations causing OI are yet known and/or tested for.
Bakers itch is a cutaneous reaction caused by bites of Acarus siro, the flour mite. See also
List of mites associated with cutaneous reactions
List of cutaneous conditions


== References ==