CIPA is caused by a genetic mutation which prevents the formation of nerve cells which are responsible for transmitting signals of pain, heat, and cold to the brain. The disorder is autosomal recessive. It is caused by a mutation in NTRK1, a gene encoding the neurotrophic tyrosine kinase receptor. NTRK1 is a receptor for nerve growth factor (NGF). This protein induces outgrowth of axons and dendrites and promotes the survival of embryonic sensory and sympathetic neurons. The mutation in NTRK1 does not allow NGF to bind properly, causing defects in the development and function of nociceptive reception. Mitochondrial abnormalities in muscle cells have been found in people with CIPA. Skin biopsies show a lack of innervation of the eccrine glands and nerve biopsies show a lack of small myelinated and unmyelinated fibers.
Characteristics of CIPA Patient