AUTOSOMAL RECESSIVE - Requires that both parents carry traits for the gene in order for it to be passed to their offspring. If both parents carry the gene (heterozygous) than there is a one in four chance of having an offspring with the complete disease and a 50% chance of the child being at least a carrier (heterozygous--like the parents). The risk to siblings of an affected individual is 25%. The same risk applies to each pregnancy regardless of the outcome of prior pregnancies. Family pedigree should be constructed before genetic counseling, and the patient should be advised of the hazard of marrying a close relative (increases the risk).