Spherocytosis is an inherited disorder of the red blood cells. It is the most common (1 in 5,000 of Northern European ancestry) disorder of the red cell membrane, the bag which contains the hemoglobin molecules that carry oxygen through the blood stream. Most cases of spherocytosis are hereditary with autosomal dominant inheritance. A few cases are apparently autosomal recessive, and interestingly enough, about 25% are though to be new mutations.