Corneal Clouding Stays Stable in Most Undergoing Mucopolysaccharidosis Treatment

Corneal clouding appears to remain stable in most patients with mucopolysaccharidosis (MPSs), including among those who received either enzyme replacement therapy (ERT) or hematopoietic stem cell transplantation (HSCT), according to research published in Cornea

“The [MPSs] are a heterogeneous group of lysosomal storage disorders in which there is a deficiency in enzymes involved in the degradation of glycosaminoglycans (GAGs). This leads to GAGs accumulating in organs throughout the body, including the eye,” explain the researchers.

With this prospective longitudinal observational study, the researchers aimed to better understand changes to corneal clouding in patients with MPS types I, II, IV, and VI using both clinical and objective imaging measures and to analyze the effect of both ERT and HSCT on corneal clouding. 

The researchers assessed corneal clouding in the eyes of each participant using slit lamp and digital slit lamp photographs for clinical grading and an iris camera for objective measures (corneal opacification measure [COM] and densitometry).

The clinical implication of these observations is that corneal opacification did not substantially improve in patients who received either ERT or HSCT.

A total of 65 patients (median age, 11.5 years) were included in the study (39 with MPS I, 5 with MPS II, 12 with MPS IV, and 9 with MPS VI) and were followed up at their routine clinical appointments in 5 to 75 months (median, 30 months). Follow-up data was collected for 45 participants (29 with MPS I, 3 with MPS II, 6 with MPS IV, and 7 with MPS VI).

The study shows that corneal clouding was stable in most participants with MPS I, II, IV, and VI during the follow-up period when measured with clinical corneal grading systems, graded digital slit lamp images, and iris camera COM scores. 

With densitometry, the researchers observed progression of corneal clouding in 12 out of 23 patients with MPS I  and 2 out of 3 patients with MPS VI. They report no notable difference in progression of corneal clouding between patients who received ERT, HSCT, or no treatment.

“This study is of particular interest and a valuable addition to the current literature due to the relatively large number of participants (given the rare nature of MPS), the variety of types of MPS explored, and the utilization of objective measures of corneal clouding,” explain the researchers. “The clinical implication of these observations is that corneal opacification did not substantially improve in patients who received either ERT or HSCT.”

Limitations of the study include the lack of statistical testing due to small sample sizes, limited follow-up duration, variable follow-up times and types of imaging among the patients, patient fatigue, and limited time for research imaging during patients’ appointments. 

Disclosure: This research was supported by BioMarin Pharmaceutical, Inc. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.