Infantile neuroaxonal dystrophy (INAD) is a rare inherited neurological disorder. It affects axons, the part of a nerve cell that carries messages from the brain to other parts of the body, and causes progressive loss of vision, muscular control, and mental skills. While the basic genetic and metabolic causes are unknown, INAD is the result of an abnormal build-up of toxic substances in nerves that communicate with muscles, skin, and the conjunctive tissue around the eyes. Symptoms usually begin within the first 2 years of life, with the loss of head control and the ability to sit, crawl, or walk, accompanied by deterioration in vision and speech.
Some children may have seizures. Distinctive facial deformities may be present at birth, including a prominent forehead, crossed eyes, an unusually small nose or jaw, and large, low-set ears. INAD is an autosomal recessive disorder, which means that both parents must be carriers of the defective gene that causes INAD to pass it on to their child. Electrophysiology (nerve conduction velocities) may be helpful for diagnosis, although diagnosis is usually confirmed by tissue biopsy of skin, rectum, nerve or conjunctive tissue to confirm the presence of characteristic swellings (spheroid bodies) in the nerve axons.
INAD is a progressive disease. Once symptoms begin, they will worsen over time. Generally, a baby’s development starts to slow down between the ages of 6 months to 3 years. The first symptoms may be slowing of motor and mental development, followed by loss or regression of previously acquired skills. Rapid, wobbly eye movements and squints may be the first symptoms, followed by floppiness in the body and legs (more than in the arms).
For the first few years, a baby with INAD will be alert and responsive, despite being increasingly physically impaired. Eventually, because of deterioration in vision, speech, and mental skills, the child will lose touch with its surroundings. Death usually occurs between the ages of 5 to 10 years.
There is no cure for INAD and no treatment that can stop the progress of the disease. Treatment is symptomatic and supportive. Doctors can prescribe medications for pain relief and sedation. Physiotherapists and other physical therapists can teach parents and caregivers how to position and seat their child, and to exercise arms and legs to maintain comfort.