Dense peripheral corneal clouding in Scheie syndrome

Ocular manifestations as key features for diagnosing mucopolysaccharidoses

Diagnosis of mucopolysaccharidosis (MPS) requires awareness of the multisystem disease manifestations and their diverse presentation in terms of time of onset and severity. Many patients with MPS remain undiagnosed for years and progressively develop irreversible pathologies, which ultimately lead to premature death. To foster timely treatment and ensure a better outcome, it is of utmost importance to recognize and evaluate the typical ocular features that present fairly early in the course of the disease in many children with MPS. These include corneal clouding, ocular hypertension/glaucoma, retinal degeneration, optic disc swelling and optic nerve atrophy. Other associations include pseudo-exophthalmos, amblyopia, strabismus and large refractive errors requiring spectacle correction. While some ocular manifestations require specialized equipment for detecting abnormalities, light sensitivity, pseudo-exophthalmos and strabismus are often apparent on a routine physical examination. In addition, patients may be symptomatic from vision impairment, photosensitivity, night blindness and visual field constriction. Combined with the skeletal/joint complications and other manifestations, these ocular features are key in the differential diagnosis of children with joint abnormalities. Rheumatologists should have a high index of suspicion for MPS to facilitate early diagnosis. Referral to a geneticist, a metabolic specialist or physician who specializes in MPS can confirm the diagnosis and provide disease management. Consultation with an ophthalmologist who has expertise in MPS is also needed for thorough examination of the eyes and regular follow-up care.

Negative ERGs in mucopolysaccharidoses (MPS) Hurler–Scheie (I-H/S) and Hurler (I-H)-syndromes

The configuration and progression of the ERG in two children with mucopolysaccharidosis (MPS) I H/S (Hurler-Scheie syndrome) and MPS I H (Hurler syndrome) is described. Physical examination, biochemical analysis, ophthalmic examination and electroretinography were performed. The Hurler-Scheie patient (case 1) showed negative scotopic but normal photopic ERGs, which remained unchanged over 2 years. The Hurler patient (case 2) showed negative scotopic and photopic ERGs which did not alter after bone marrow transplantation (BMT). One year after BMT, further b-wave amplitude reduction had caused the ERGs to become more negative. The electronegative configuration of the ERGs suggests that, in these cases of MPS, the primary retinal abnormality in MPS I may be faulty synaptic transmission from photoreceptors to more proximal elements, deficient bipolar responsivity, or Muller cell disease. Further degradation with time suggests the defect to be progressive with BMT causing little or no improvement. In the Hurler-Scheie syndrome case, the defect appears to spare the cone system and to show little or no progression.

The first 5 years of clinical experience with laronidase enzyme replacement therapy for mucopolysaccharidosis I

Mucopolysaccharidosis I (MPS I, McKusick 25280) is caused by the deficiency or absence of the lysosomal enzyme, alpha-L-iduronidase (EC 3.2.1.76). This inherited disease causes progressive cellular, tissue and organ damage across the entire phenotypic spectrum. Disabling, multi-organ disease is the rule, and generally results in death between the first and fourth decades of life. Recently, laronidase (Aldurazyme) [Genzyme], a specific recombinant human alpha-L-iduronidase) became commercially available as long-term enzyme replacement therapy. Results from the Phase I/II and III extended clinical studies have shown that laronidase safely and effectively alleviates many systemic signs and symptoms of this progressive multisystemic disease. Clinically meaningful and sustained improvements in pulmonary function and functional capacity have been observed in Phase III study patients. Significant and sustained reductions in urinary glysosaminoglycan (GAG) excretion and hepatomegaly have also been observed. Improvements in sleep apnoea and joint range of motion occurred in patients with the most severe symptoms at baseline. Improvements in Disability Index scores as measured using the CHAQ and HAQ questionnaires were modest, which may have been related to the fact that these disability measuring tools are not disease-specific. Anecdotal reports of improvements in the performance of daily activities further add to the therapeutic benefits, as do case histories pointing at stabilisation or improvement of symptomatology in various organs, such as the eyes, heart, and muscles. With the availability of specific treatment, the importance of early recognition of the disease and appropriate therapeutic intervention has increased. The variability in clinical symptomatology is reviewed in detail and may allow for a better understanding of the diagnostic and therapeutic challenges. Results of the clinical trials and their initial extension periods, as well as the anecdotal experiences of physicians with laronidase in non-study settings, are discussed.