 
 Society for Mucopolysaccharide © 2009
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  ML II and III
ML II (Mucolipidosis II) and ML III (Mucolipidosis III)ML II (also known as I-Cell disease) and ML III (also known as Pseudo-Hurler Polydystrophy) were once thought to be two separate forms of a condition known as Mucolipidosis. It is now known that both ML II and ML III have the same biochemical cause and that they represent two ends of a spectrum of severity. The name I-Cell in Mucolipidosis type II comes from the characteristic appearance of the cells under a microscope. One of the first doctors to write about the condition in the 1960s was Dr Jules Leroy from Belgium and his name is sometimes used to refer to ML II. ML III was described in 1966 by Dr Maroteaux and Dr Lamy from France. They called it Pseudo-Hurler Polydystrophy as it resembled a mild form of Hurler disease, one of the mucopolysaccharide diseases. 'Polydystrophy' means that many organs are abnormal. What causes ML II and ML III?Many complex chemicals are used in the building of cells in the body. There is a continuous process in the body of replacing used materials and breaking them down for disposal. This activity takes place in a special part of the body's cells called the lysosome. Substances known as enzymes which are responsible for breaking down the used material can only reach the lysosomes after a special signal has been attached to them. In ML II and ML III the signal is not attached so the enzymes cannot get to the right place and are lost outside the cell. How common is ML II and ML III?The MPS Society which co-ordinates the Registry for Mucopolysaccharide and Related Diseases has shown that in the United Kingdom between 1980 and 1990 23 babies were born with ML II and 14 with ML III. This gives a live birth figure of 1: 326,000 for ML II and 1: 536,000 for ML III. How are ML II and ML III inherited?We all have genes inherited from our parents which control whether we are tall, short, fair, etc. Some genes we inherit are 'recessive', that is to say we carry the gene but it does not have any effect on our development. ML II and ML III are caused by a recessive gene. If an adult carrying the abnormal gene has a partner who is another carrier there will be a one in four chance with every pregnancy that the child will inherit the defective gene from each parent and will suffer from the disease. There is a two in three chance that unaffected brothers and sisters of ML sufferers will be carriers. They can be reassured however that, as the disease is so rare, the chance of having a partner who is another carrier is very slight provided their partner is not a cousin or other close family member. All families of affected children should seek further information from their doctor or from a genetic counsellor before planning to have more children. There is a more detailed explanation of this complex subject in a booklet available from the MPS Society on the Pattern of Inheritance in MPS diseases. Please visit our Information Resource section. Prenatal diagnosisIf you already have a child with ML II or ML III it is possible to have tests during a subsequent pregnancy to find out whether the baby you are carrying is affected. It is important to consult your doctor as soon as you suspect you may be pregnant if you wish tests to be arranged. Further informationThere are detailed booklets on ML II and ML III produced by the MPS Society in collaboration with parents and doctors drawing on their experience and with reference to medical literature. The booklets include detailed information on the presentation and clinical management of the disease and treatment options available. Please visit our Information Resource section. |
