On pain inheritance
Several evidences have documented the importance of genetic factors in a number of clinical conditions characterized by chronic pain. Significant family associations were in fact demonstrated in many disorders, such as fibromyalgia, irritable bowel syndrome, headaches, some chronic arthritis, and some surveys on twins suggest that genetic factors may play an important role in chronic widespread pain and low back pain.
A significant number of genes that modulate nociception were identified as risk factors for an altered processing of pain and the resulting development of neuropathic pain: genes coding for opioid receptors, transient receptors cation channels, NMDA receptors, it has been demonstrated as well an association between COMT polymorphism (an enzyme assigned to control the metabolism of catecholamines) and TRPV1 and the degree of perceived pain. Other studies have also shown a correlation between a gene that encodes dopamine D4 receptor and the development of fibromyalgia.
Probably, next to genetic factors, environmental factors – associated with them or in cooperation with them – play an important role. A research team at King’s College (London) studied identical and non- homozygote twins and found in homozygote a different DNA haplotype and, again, the clinical spectrum of pain appeared significantly different.
Genetic differences, in a broad sense, can not only characterize the different types and the different degree of pain, but they also appear able to differentiate the response to analgesic therapy. For example, female gender shows a more modest threshold for pain, as well as in Hispanic ethnic groups is documented a higher prevalence of chronic pain, compared to non-Hispanic populations.
Finally, the pain specialist should also evaluate these characteristics of gender, ethnicity and familiarity at the time of diagnosis and treatment plan for a patient with pain.
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