The mucopolysaccharidoses (MPSs) are a group of lysosomal storage disorders, caused by the deficiency of lysosomal enzymes needed to degrade glycosaminoglycan (GAG). Mucopolysaccharidosis type I (MPS I); also known as Hurler, Hurler-Scheie and Scheie syndrome, is an autosomal recessive disorder caused by the deficiency of an enzyme called alpha-L-iduronidase. Deficiency of this enzyme results in the accumulation of dermatan sulfate and heparan sulfate that are complex sugars known as glycosaminoglycans (GAGs). This deficiency, in turn, results in the accumulation of GAGs in the lysosomes leading to progressive, multi-system organ damage.
MPS I is relentlessly progressive and potentially fatal, although the severity of symptoms widely varies. It is categorized into Hurler syndrome (MPS IH), the most severe, Scheie syndrome (MPS IS), the mildest and Hurler-Scheie syndrome (MPS IHS), with an intermediate phenotype. In some patients the brain may be affected in combination with physical symptoms; others may develop physical symptoms with no brain involvement. Physical symptoms may include eye and hearing problems, bone and joint malformation, and heart and breathing difficulties. In Hurler syndrome the age of onset occurs 6-8 months after birth, with skeletal deformities and a delay in motor and intellectual development being the leading symptoms. Other symptoms may include corneal clouding, organomegaly, heart disease, short stature, hernias, facial dysmorphism and hirsutism. In Scheie syndrome, the adult-onset, patients are of almost normal height and do not show intellectual deficiency. Typical symptoms include stiff joints, corneal opacities, carpal tunnel syndrome and mild skeletal changes. Patients with Hurler-Scheie syndrome have normal or almost normal intelligence, but exhibit various degrees of physical impairment.
Diagnosis of MPS I is based on measuring mucopolysaccharides in urine, followed by measurement of enzyme activity in blood. Mutation testing for conformation may also be possible. There is no cure for MPS diseases, but early treatment can slow the progression of the disease.
Alif et al. (2000) investigated 16 Moroccan patients (3-20 years old) with MPS over a period of three years (June 1996-May 1999). These 16 patients belonged to 12 families, nine of which were consanguineous (75%). Of these 16 patients, 12 came from the Souss region. Twelve patients had Hurler syndrome and three had Hurler/Scheie's syndrome. Short stature, coarse face, organomegaly, hernia, cardiac disease, mental delay and dysostosis were observed in variable degrees. At the molecular level, the p.P533R mutation in the IDUA gene was detected in 24 among 26 alleles studied.
[See: United Arab Emirates > Al-Jasmi et al., 2013].
Al-Jasmi et al. (2013) studied the prevalence of lysosomal storage diseases (LSDs) in the UAE and reported their mutation spectrum. This study included all the patients diagnosed and followed up between 1995 and 2010 at the only two metabolic referral centers in the country. In this period, a total of 119 patients, 65 of them Emiratis, were diagnosed with LSDs. Four patients with MPS Type I were identified in this study; one of them being an Emirati, giving a comparatively low birth prevalence of 0.25 per 100,000 for Emiratis. Of the remaining patients, at least one was of Palestinian origin, and showed a severe form of the disease with CNS involvement.