Support group for MPS & Gaucher - Inheritance, Diagnosis & Treatment
Mode of inheritance
MPS has a hidden or recessive mode of inheritance, and it shows up only when both the genes of the pair (derived from each of the parent) in an individual are affected viz. both the genes responsible for the production of enzymes are at fault in the affected. It is enough if one has one functioning gene to generate adequate enzyme to conduct a function well; i.e. half as much enzyme can do twice the usual amount of work. All types of MPS mentioned above other than Hunter Syndrome (MPS ll) have the same pattern of inheritence, while Type ll alone is X-linked and abnormality in the maternal gene component contributes to this problem.
In other words, the parents of the affected child will have one functional gene that does the work. There is a 25% recurrence risk in subsequent pregnancies and 75% chance to result in a child having one normal gene and not be affected by the disorder.
Diagnosis of MPS
Urine screening to estimate the levels of GAGs ( MPS substances) such as dermatan sulfate, heparan sulfate, keratan and chondroitin sulfate that are excreted, is the first step to identify the problem of MPS after clinical examination of the affected. Confirmation of the particular type of disorder is done by enzyme assays in white blood cells (leukocytes) or serum or fibroblast culture (skin biopsy). Prenatal diagnosis of all types of MPS is possible by estimating the enzyme levels in Chorionic villi biopsy done between 11-13 weeks and Amniocentesis done between 16-20 weeks of gestation.
Treatment of MPS disorders
Type I - Presently Enzyme Replacement Therapy (ERT) & Bone Marrow Transplant (BMT) are the only treatments available for Type I MPS. BMT is the permanent cure found to be successful if done in children within 2 years of age. Early pick up of the affected ensures timely action and good results. ERT is effective in children with Hurler Scheie (Type I - H/S) / Scheie type ( Type I/S) disorders. Genzyme, USA, magnanimously facilitates ERT totally free of cost through their India Charitable Access Program ( INCAP) to Type I MPS patients with confirmed diagnosis. But for this, ERT would be beyond the reach of our patients, as it is a lifelong treatment process and the cost of the drug is unaffordable.
Type II & VI - ERT for Type II & VI are the recent innovations by Shire & Biomarin Pharmaceuticals respectively. These are available only in the West across USA, UK & EU. As there is no charity access in the offing by these companies right now, patients in the other nations are unable to get the benefits of the treatment. ERT in general is useful to alleviate the present symptoms in the affected & delays the progress of the disease.
Prognosis and morbidity:
Survival rate of the MPS affected individuals vary from early childhood to early adulthood and rarely some type like MPS Scheie has normal life span. Morbidity is proportionately related to the severity of the problem and it requires supportive medical care.