This also means that a sibling of a patient with Pendred syndrome has a 25% chance of also having the condition if the parents are unaffected carriers.It has been linked to mutations in the PDS gene, which codes for the pendrin protein (solute carrier family 26, member 4, SLC26A4). The gene is located on the long arm of chromosome 7 (7q31). Mutations in the same gene also cause enlarged vestibular aqueduct syndrome (EVA or EVAS), another congenital cause of deafness; specific mutations are more likely to cause EVAS, while others are more linked with Pendred syndrome. Pathophysiology
SLC26A4 can be found in the cochlea (part of the inner ear), thyroid and the kidney. In the kidney, it participates in the secretion of bicarbonate. However, Pendred syndrome is not known to lead to kidney problems. It functions as an iodide/chloride transporter. In the thyroid, this leads to reduced organification of iodine (i.e. its incorporation into thyroid hormone). Diagnosis
People with Pendred syndrome present with a hearing loss either at birth or during childhood. The hearing loss is commonly progressive. In early stages it is usually a mixed hearing loss (both conductive and sensorineural hearing loss) because of a third window effect due to the inner ear malformation (widened vestibular aqueducts). A thyroid goitre may be present in the first decade and is usual towards the end of the second decade.
Acute motor axonal neuropathy (AMAN) is a variant of Guillain–Barré syndrome. It is characterized by acute paralysis and loss of reflexes without sensory loss. Pathologically, there is motor axonal degeneration with antibody-mediated attacks of motor nerves and nodes of Ranvier. Signs and symptoms
Causes
A link to Campylobacter jejuni was suspected when a young girl was admitted to Second Teaching Hospital. She had become ill after feeding the family chickens. She developed acute paralysis and respiratory failure. Investigators discovered that several of the chickens in the home displayed similar symptoms and C. jejuni was found in their droppings. Several of the paralysis patients were found to have antibodies to C. jejuni and anti-GD1a antibodies, suggesting a link between the pathogen and the disease. In 2015, Zika virus was linked to AMAN. Diagnosis
The syndrome typically presents as a progressive flaccid symmetric paralysis with areflexia, often causing respiratory failure. Electromyographic studies and nerve conduction studies show normal motor conduction velocity and latency with decreased amplitude of compound muscle action potentials. Pathologically, it is a noninflammatory axonopathy without demyelination. Antibodies attack the coating of the motor neurons without causing inflammation or loss of myelin. It does not affect sensory neurons, so sensation remains intact despite loss of movement. Treatment
the majority of patients have complete symptom resolution with 5-day intravenous immunoglobulin (IV Ig) treatment. Patients with AMAN continue to see improvements in ambulation and functional ability up to four years post-diagnosis.