Andermann syndrome

Andermann syndrome is a disorder that damages the nerves used for muscle movement and sensation (motor and sensory neuropathy). The neuropathy in this condition is due to poor development of nerves, particularly nerves that control movement, which are half their normal size. Absence (agenesis) or malformation of the tissue connecting the left and right halves of the brain (corpus callosum) occurs in most people with this disorder. Because of these features, Andermann syndrome is sometimes referred to as hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC).

People affected by Andermann syndrome have abnormal or absent reflexes (areflexia) and weak muscle tone (hypotonia). They experience muscle wasting (amyotrophy), severe progressive weakness and loss of sensation in the limbs, and rhythmic shaking (tremors). 

People with Andermann syndrome typically begin walking between ages 3 and 4, and worsening neuropathy causes them to lose this ability by their teenage years. As they get older, people with this disorder frequently develop joint deformities called contractures, which restrict the movement of certain joints. Most affected individuals also develop abnormal curvature of the spine (scoliosis), which may require surgery.

Andermann syndrome also results in abnormal function of certain cranial nerves, which emerge directly from the brain and extend to various areas of the head and neck. Cranial nerve problems may result in facial muscle weakness, drooping eyelids (ptosis), and difficulty following movements with the eyes (gaze palsy).

Individuals with Andermann syndrome usually have intellectual disability, which may be mild to severe, and some experience seizures. They may also develop psychiatric symptoms such as depression, anxiety, agitation, paranoia, and hallucinations, which usually appear in adolescence.

Some people with Andermann syndrome have atypical physical features such as widely spaced eyes (ocular hypertelorism); a wide, short skull (brachycephaly); a high arch of the hard palate at the roof of the mouth; a big toe that crosses over the other toes; and partial fusion (syndactyly) of the second and third toes.

Andermann syndrome is associated with a shortened life expectancy related to respiratory insufficiency, but affected individuals typically live into adulthood.