SNP Shot: Genomic Insights

Pendred syndrome is a condition often characterized by hearing impairment and the development of a goiter, which is an enlarged thyroid gland. The thyroid, located at the base of the neck, is shaped like a butterfly and produces hormones. Goiters in individuals with Pendred syndrome typically appear between late childhood and early adulthood. In the majority of cases, the enlarged thyroid functions normally.

Most people with Pendred syndrome experience severe to profound hearing loss, often present from birth (sensorineural hearing loss), due to changes in the inner ear. Less frequently, hearing loss develops later in infancy or early childhood. Some individuals with Pendred syndrome also experience balance problems resulting from dysfunction of the vestibular system, the inner ear component responsible for maintaining balance and spatial orientation.

A hallmark of Pendred syndrome is an inner ear abnormality known as an enlarged vestibular aqueduct (EVA). The vestibular aqueduct is a bony channel connecting the inner ear to the skull's interior. Some individuals also exhibit an abnormally shaped cochlea, the snail-shaped structure within the inner ear crucial for sound processing. The coexistence of an enlarged vestibular aqueduct and an abnormally shaped cochlea is referred to as Mondini malformation.

Pendred syndrome has overlapping characteristics with other conditions involving hearing loss and thyroid abnormalities. It's debated whether these are distinct disorders or represent a range of related symptoms. These conditions include DFNB4, a type of non-syndromic hearing loss (hearing loss without other bodily effects), and, rarely, congenital hypothyroidism caused by an underdeveloped thyroid gland (thyroid hypoplasia). All these conditions stem from mutations in the same gene.

Inheritance:

Pendred syndrome follows an autosomal recessive inheritance pattern. This means that an individual must inherit two copies of the mutated gene, one from each parent, to develop the condition. The parents, who each carry one copy of the mutated gene, usually do not exhibit any signs or symptoms of Pendred syndrome.