Ragged Red Fiber
As ragged red fiber abbreviated RRF (in German about shaggy, red fibers), mitochondria clumped together in a light microscopic examination of a biopsy according to Gömöri trichrome staining are called. They arise in various diseases of the mitochondria through their reproduction. Most of the diseases are mutations in the mitochondrially encoded enzymes in the respiratory chain, such as in Leigh syndrome or MERRF syndrome .
The number of ragged red fibers in a biopsy increases with age. RRF is not found in humans under the age of three. 1–2% RRF in a biopsy suggests mitochondrial myopathy . But there are also mitochondrial myopathies in which no RRF can be found, usually when the defect is not in the respiratory chain.
Ragged red fibers do not necessarily indicate a mitochondrial disease. They also occur in other diseases that are not caused by a disorder of the mitochondria, but in which the mitochondria are involved in the disease process, e.g. B. in myositides , different myopathies also z. B. due to antiretroviral therapy.
In electron microscopy , paracrystalline inclusions can be found as an expression of the failed mitochondrial creatine kinase .
