Corneal clouding in the genetic mucopolysaccharidoses: a cell culture study

Natural history and clinical assessment of Taiwanese patients with mucopolysaccharidosis IVA

Background

Mucopolysaccharidosis IVA (MPS IVA) is a rare lysosomal storage disorder caused by N-acetylgalactosamine-6-sulfatase deficiency, which catalyzes a step in the catabolism of glycosaminoglycans, keratan sulfate and chondroitin-6-sulfate. This disease has a variable age of onset and rate of progression.

Methods

A retrospective analysis of medical records of 24 patients with MPS IVA (11 males, 13 females; current mean age ± SD, 12.6 ± 6.6 years; age range, 1.4-29.4 years) seen at 6 medical centers in Taiwan from January 1996 through June 2013 was performed.

Results

Mean ages of onset of symptoms and confirmed diagnosis were 2.0 ± 1.6 and 5.7 ± 4.5 years, respectively. The most prevalent clinical manifestations were kyphosis (100%), pectus carinatum (96%), abnormal gait (93%), striking short trunk dwarfism (92%), genu valgum (92%), and valvular heart disease (91%). Eight patients (33%) experienced at least one surgical procedure with the most common being ear tube insertion (25%), adenoidectomy (17%), tonsillectomy (13%), supraglottoplasty (13%), spinal decompression (13%), and spinal fusion (13%). The most prevalent cardiac valve abnormalities were aortic stenosis (45%) and mitral regurgitation (45%). At the time of the study, 8 out of 24 patients (33%) have died at the mean age of 17.2 ± 7.7 years.

Conclusions

An understanding of the natural history involved in MPS IVA may allow early diagnosis of the disease. All affected Taiwanese patients experienced significant functional limitations. Adequate evaluations and timely management may improve clinical outcomes and quality of life.

Clinical overview and treatment options for non-skeletal manifestations of mucopolysaccharidosis type IVA

Mucopolysaccharidosis type IVA (MPS IVA) or Morquio syndrome is a multisystem disorder caused by galactosamine-6-sulfatase deficiency. Skeletal manifestations, including short stature, skeletal dysplasia, cervical instability, and joint destruction, are known to be associated with this condition. Due to the severity of these skeletal manifestations, the non-skeletal manifestations are frequently overlooked despite their significant contribution to disease progression and impact on quality of life. This review provides detailed information regarding the non-skeletal manifestations and suggests long-term assessment guidelines. The visual, auditory, digestive, cardiovascular, and respiratory systems are addressed and overall quality of life as measured by endurance and other functional abilities is discussed. Impairments such as corneal clouding, astigmatism, glaucoma, hearing loss, hernias, hepatomegaly, dental abnormalities, cardiac valve thickening and regurgitation, obstructive sleep apnea, tracheomalacia, restrictive and obstructive respiratory compromise, and muscular weakness are discussed. Increased awareness of these non-skeletal features is needed to improve patient care.

Corneal dystrophies. I. Dystrophies of the epithelium, Bowman's layer and stroma

Most corneal dystrophies are autosomal dominant, bilateral disorders that primarily affect one layer of an otherwise normal cornea, progress slowly after their appearance in the first or second decade, and are not associated with a systemic disease. Epithelial basement membrane dystrophy and Fuchs' endothelial dystrophy are seen commonly by the general ophthalmologist; fleck, posterior polymorphous, granular or lattice dystrophies are seen more rarely, and others may never be seen in general office practice. While the distinctive clinical appearance of most corneal dystrophies allows accurate diagnosis, the integration of slitlamp findings with histopathologic and biochemical findings aids in the understanding of the clinical observations and provides a more rational basis for therapy. Transmission electtron microscopy is the most accurate method of histopathologic diagnosis. Epithelial dystrophies usually manifest intraepithelial cysts and abnormal basement membrane. In stromal dystrophies, an abnormal substance accumulates within the keratocytes or among the collagen fibrils; it may be an excess normal metabolite (like glycosaminoglycans in macular dystrophy), a material not usually present (like amyloid in lattice dystrophy), or a substance of unknown composition (like hyaline in granular dystrophy). Each dystrophy is illustrated with a composite drawing. Endothelial dystrophies will be reviewed separately in a second article.

Mucopolysaccharidosis II (Hunter disease) with corneal opacities. Report on two patients at the extremes of a wide clinical spectrum

Clinically visible corneal opacities were observed in a patient with an extremely severe form of mucopolysaccharidosis II. In a second patient with an unusually mild form of mucopolysaccharidosis II, discrete corneal opacities were detected by slit-lamp examination. Thus clear corneae can no longer be regarded as a hallmark of mucopolysaccharidosis II.