Giant axonal neuropathy is a rare, autosomal recessive neurological disorder that causes disorganization of neurofilaments. Neurofilaments form a structural framework that helps to define the shape and size of neurons and are essential for normal nerve function. A distinguishing feature is its association with kinky, or curly, hair; in such cases it has been called Giant axonal neuropathy with curly hair. Genetics
Giant axonal neuropathy results from mutations in the GAN gene, which codes for the protein gigaxonin. This alters the shape of the protein, changing how it interacts with other proteins when organizing the structure of the neuron.Neurons affected by the altered protein accumulate excess neurofilaments in the axon, the long extension from the nerve cell that transmits its signal to other nerve cells and to muscles. These enlarged or giant axons cannot transmit signals properly, and eventually deteriorate, resulting in the range of neurological anomalies associated with the disorder.This disease is an autosomal recessive disorder, which means the defective gene is located on an autosome, and both parents must have one copy of the defective gene in order to have a child born with the disorder. The parents of a child with an autosomal recessive disorder are carriers, but are usually not affected by the disorder. Diagnosis
Giant axonal neuropathy usually appears in infancy or early childhood, and is progressive. Early signs of the disorder often present in the peripheral nervous system, causing individuals with this disorder to have problems walking. Later, normal sensation, coordination, strength, and reflexes become affected.
Life cycle
The adult Spirometra live in the small intestine of the definitive host—a dog, cat, raccoon, or other mammal—for up to 9 years, where they produce many eggs. When the host defecates, the unembryonated eggs leave the body in the feces and hatch when they reach fresh water. The eggs are eaten by copepods (crustaceans of the genus Cyclops), which are the first intermediate hosts. In the copepods, the eggs develop into procercoid larvae that live in the body cavity. The second intermediate hosts include fish, reptiles, or amphibians that consume the copepods. The larvae penetrate the intestinal tract of the second intermediate host, where they become plerocercoid larvae and proliferate to the subcutaneous tissues and muscles. The second intermediate host is eventually eaten by a definitive host predator, such as a dog, and the cycle begins again. Humans are accidental hosts in the cycle, becoming infected with the plerocercoid larvae by contact with or ingestion of the first or second intermediate hosts. The larvae migrate to the subcutaneous tissues in humans; however, no development takes place and the human is not capable of transmitting the disease. In S. proliferum, many larvae, rather than just a few, proliferate throughout the subcutaneous tissues of humans. Diagnosis
Sparganosis is typically diagnosed following surgical removal of the worms, although the infection may also be diagnosed by identification of eosinophilia or identification of the parasite in a tissue specimen. If such biopsy and excision procedures are not feasible, the antisparganum ELISA test may be used.