Effects of ML4 on the eye

3 October 2023 | Fiona Rowe (Prof) | EYE - Paediatrics, EYE - Strabismus

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Mucolipidosis type IV (ML4) is an autosomal recessive lysosomal storage disease and is caused by variants of the MC0LN1 gene. It often presents in young individuals with eye and ocular adnexa issues. The authors present a case report and literature review with the aim to improve understanding of the disease. The literature review, undertaken in 2020, identified 314 articles and extracted information on 95 patients with ML4; 94 with genetic / biopsy confirmation. Ophthalmology information was reported for 93 patients, including the author’s case report, and 91/93 had an eye abnormality. There was a complete range from mild non-specific issues to light perception vision. Bilateral corneal clouding was noted in 90.3%, caused by build-up of lysosomal storage bodies in the corneal epithelium. Optic nerve pallor was noted in 52.2%, retinal dystrophy / pigmentary changes in 50.5%, and retinal vascular attenuation in 38.9%. Visual prognosis mostly depends on progressive fundal changes. The typical condition (in Ashkenazi Jewish descent) causes blindness by the end of the first decade of life. An atypical form (non-Ashkenazi Jewish descent) is often milder and with less effect on the eye. Therefore, background information is important when considering prognosis decisions. Symptoms included ocular pain, photophobia and lacrimation in 19.4% and were possibly due to corneal erosion. Strabismus was present in 58.1% and nystagmus was also common. Less common findings included eyelid swelling, ptosis and cataracts. The authors clarify the importance of early diagnosis, treatment planning and genetic counselling.