Coccydynia is a medical term meaning pain in the coccyx or tailbone area, often brought on by a fall onto the coccyx or by persistent irritation usually from sitting. Synonyms
Coccydynia is also known as coccygodynia, coccygeal pain, coccyx pain, or coccalgia. Anatomy
Structure
Coccydynia occurs in the lowest part of the spine, the coccyx, which is believed to be a vestigial tail, or in other words the “tail bone”. The name coccyx is derived from the Greek word for cuckoo due to its beak like appearance. The coccyx itself is made up of 3 to 5 vertebrae, some of which may be fused together. The ventral side of the coccyx is slightly concave whereas the dorsal aspect is slightly convex. Both of these sides have transverse grooves that show where the vestigial coccygeal units had previously fused. The coccyx attaches to the sacrum from the dorsal grooves, with the attachment being either a symphysis or as a true synovial joint, and also to the gluteus maximus muscle, the coccygeal muscle, and the anococcygeal ligament. Orientations of the coccyx
There are four different orientations for the coccyx, as described by Postacchini and Massobrio. In type I the coccyx is curved anteriorly with its apex facing downward and caudally. In type II this forward curvature is more dramatic and the apex extends forward. Type III is where the coccyx angles forward sharply. Lastly, type IV is characterized by the coccyx being subluxated at the sacrococcygeal joint. Pathophysiology
There are common pathophysiological ways that a person may develop coccydynia.
The initial manifestation of MEN2 was medullary thyroid carcinoma in 60% of patients, medullary thyroid carcinoma synchronous with pheochromocytoma in 34% and pheochromocytoma alone in 6%. 72% had bilateral pheochromocytomas. Causes
The table in the multiple endocrine neoplasia article lists the genes involved in the various MEN syndromes. Most cases of MEN2 derive from a variation in the RET proto-oncogene, and are specific for cells of neural crest origin. A database of MEN-implicated RET mutations is maintained by the University of Utah Department of Physiology.The protein produced by the RET gene plays an important role in the TGF-beta (transforming growth factor beta) signaling system. Because the TGF-beta system operates in nervous tissues throughout the body, variations in the RET gene can have effects in nervous tissues throughout the body. MEN2 generally results from a gain-of-function variant of a RET gene. Other diseases, such as Hirschsprung disease, result from loss-of-function variants. OMIM # 164761 lists the syndromes associated with the RET gene. Genetics
When inherited, multiple endocrine neoplasia type 2 is transmitted in an autosomal dominant pattern, which means affected people have one affected parent, and possibly affected siblings and children. Some cases, however, result from spontaneous new mutations in the RET gene. These cases occur in people with no family history of the disorder. In MEN2B, for example, about half of all cases arise as spontaneous new mutations.