A form of tertiary syphilis, affecting men more frequently than women, which appears some years (five to thirty) after the primary infection. It is now very rare.
Degeneration occurs in the sensory nerves, which originate in the spinal cord, producing impairment of sensation of temperature and pain and loss of tendon reflexes. Episodes of sudden, severe pain may develop in the arms or legs for no apparent reason. Loss of the ability to feel pain and temperature occurs on the underside of the forearm and arm and spreads over the chest. The abdomen is usually normal, but there is loss of sensation in the legs.
The victim cannot tell where his legs are when his eyes are closed, and he has to keep his eyes open in order to maintain his balance. He develops a characteristic gait with the feet wide apart, and because he has lost sensation in the soles of his feet he picks them up high when he walks and stamps them down. The same loss of sensation leads to damage of the joints and painless ulcers on the soles of the feet. Sensation from the bladder may be lost, so that the person suffers from painless retention of urine, and he may be constipated. In some cases there are attacks of acute abdominal pain, with vomiting, which may mimic an acute abdominal emergency.
The difficulty in walking gives the disease its alternative name, locomotor ataxia.