Abetalipoproteinaemia is a rare inherited disorder where certain fats such as cholesterol and fat-soluble vitamins cannot be metabolized by the body. This leads to progressive neurological deterioration, movement problems, eye issues and abnormal blood cells. Symptoms begin to appear within the first month of life. Because the affected infant cannot absorb and metabolize certain fats they fail to gain weight and do not grow at the expected rate. They often have diarrhea and fatty, foul-smelling stool. As they age, affected individuals have a progressively harder time controlling their movements, lose their coordination and their muscles weaken. They also develop a degenerating condition that affects the retina of the eyes that could lead to vision loss, called retinitis pigmentosa. Their blood cells also appear as abnormal star-shaped cells instead of round discs. Intellect is typically not affected but cases of intellectual disability have been reported with abetalipoproteinaemia. Affected individuals can live into adulthood, though life expectancy is reduced. There is no cure for abetalipoproteinaemia, but medical care and surveillance can help to improve some symptoms and overall condition of life. Abetalipoproteinaemia is caused by pathogenic mutations in the MTTP gene.