Symptoms of this disorder commonly appear between one and two years of age. Symptoms include mildly coarsened facial features, deafness, ichthyosis[7] and an enlarged liver and spleen (hepatosplenomegaly).[8] Abnormalities of the skeleton, such as a curving of the spine and breast bone may occur. The skin of individuals afflicted with this disorder, is typically dry.[9] Children affected by this disorder develop more slowly than normal and may display delayed speech and walking skills.[9]
The disease is fatal, with symptoms that include neurological damage and severe mental retardation.[10] These sulfatase enzymes are responsible for breaking down and recycling complex sulfate-containing sugars from lipids and mucopolysaccharides within the lysosome. The accumulation of lipids and mucopolysaccharides inside the lysosome results in symptoms associated with this disorder. As of 2018[update], 75–100 cases of MSD had been reported worldwide.[9]
Causes
Multiple sulfatase deficiency is caused by any mutation of the SUMF1 gene which renders its protein product, the formylglycine-generating enzyme (FGE), defective.[11][12] These mutations result in inactive forms of FGE.[13] This enzyme is required for posttranslational modification of a cysteine residue in the sulfatase enzyme active site into formylglycine,[14] which is required for its proper function.[15]
Genetics
MSD has an autosomal recessive inheritance pattern.[2]
The inheritance probabilities per birth are as follows:
If both parents are carriers:
25% (1 in 4) children will have the disorder
50% (2 in 4) children will be carriers (but unaffected)
25% (1 in 4) children will be free of MSD - unaffected child that is not a carrier
If one parent is affected and one is free of MSD:
0% (0) children will have the disorder - only one parent is affected, other parent always gives normal gene
100% (4 in 4) children will be carriers (but unaffected)
If one parent is a carrier and the other is free of MSD:
50% (2 in 4) children will be carriers (but unaffected)
50% (2 in 4) children will be free of MSD - unaffected child that is not a carrier
Diagnosis
MSD may be diagnosed when deficiency of more than one sulfatase enzyme is identified in leukocytes or fibroblasts,[16] or by molecular genetic testing which shows pathogenic variation in both alleles of the SUMF1 gene.[9]
Treatment
As there is no cure for MSD, treatment is restricted to management of symptoms.[16]
There is much research on MSD that is currently underway. MSD Action Foundation have initiated more than 15 research projects on MSD in the last 6 years. Many of these have a translational focus. It is hoped that clinical trials for MSD will happen in the not too distant future- Alan Finglas. [Ref 17. Finglas 2020]
[17] View from inside: When multiple sulfatase deficiency changes everything about how you live and becomes your life
Alan Finglas,
https://doi.org/10.1002/jimd.12305