2020–2021 BCSC Basic and Clinical Science Course™
6 Pediatric Ophthalmology and Strabismus
Part II: Pediatric Ophthalmology
Chapter 28: Ocular Manifestations of Systemic Disease
Inborn Errors of Metabolism
Inborn errors of metabolism are estimated to occur in 1 in 1400 births and are typically caused by biallelic mutations. Ocular findings can result from direct toxicity of abnormal metabolic products, accumulation of abnormal (or normal) metabolites, errors of synthetic pathways, or deficient production of energy. The age at onset of ocular manifestations of inborn errors of metabolism varies. Table 28-2 summarizes the common ophthalmic manifestations of select conditions. Also see Chapter 21. Following are examples of ocular structural abnormalities secondary to metabolic disorders:
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Corneal clouding or deposits: certain mucopolysaccharidoses (Fig 28-1), cystinosis (Fig 28-2), Schnyder corneal dystrophy (Fig 28-3)
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Corneal pseudodendritic ulcerations: tyrosinemia
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Cataracts: diabetes mellitus, galactosemia, Smith-Lemli-Opitz syndrome, cerebrotendinous xanthomatosis (Fig 28-4)
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Lens luxation or subluxation: homocystinuria (Fig 28-5)
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Retinal degeneration: peroxisomal disorders (Zellweger syndrome, Refsum disease), lysosomal disorders (eg, neuronal ceroid lipofuscinosis), mitochondrial disorders (eg, Kearns-Sayre syndrome [Fig 28-6])
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Central macular cherry-red spot: GM2 gangliosidosis type I (Tay-Sachs disease) and type II (Sandhoff disease), Niemann-Pick disease. The cherry-red spot disappears over time as the intumescent ganglion cells die and optic atrophy develops. Therefore, the absence of a cherry-red spot should not be used to rule out a diagnosis, especially in older children.
Table 28-1 Common Chromosomal Abnormalities With Ocular Associations
Table 28-2 Ocular Findings in Mucopolysaccharidoses, Mucolipidoses, Lipidoses, Gangliosidoses, and Miscellaneous Disorders
In some disorders, early metabolic control greatly decreases the risk of ocular and systemic sequelae. Therefore, early recognition of metabolic disorders and timely referral to a geneticist are essential. The ophthalmologist can play a key role in the early identification of certain treatable metabolic disorders, examples of which are galactosemia, classic homocystinuria (Chapter 23), cystinosis (Chapter 21), certain mucopolysaccharidoses, and cerebrotendinous xanthomatosis (Chapter 23).
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.