Mucopolysaccharidosis: Can Other Types Occur After Screening? - Pediatrics

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Mucopolysaccharidosis (MPS) refers to a group of inherited metabolic disorders caused by the deficiency of specific enzymes needed to break down glycosaminoglycans (GAGs), which are complex carbohydrates. The most common types of MPS include MPS I (Hurler syndrome), MPS II (Hunter syndrome), and others such as MPS III (Sanfilippo syndrome), MPS IV (Morquio syndrome), MPS VI (Maroteaux-Lamy syndrome), and MPS VII (Sly syndrome). Each type has its own unique clinical features and progression.

In your case, your child has undergone newborn screening for MPS I and MPS II, both of which returned normal results. However, it is important to understand that the newborn screening tests typically focus on a limited number of conditions, and while they are effective at identifying the most common types of MPS, they may not detect all possible forms of the disorder.
To answer your question, yes, it is possible for other types of MPS to occur even if the newborn screening for MPS I and MPS II was normal. This is because the screening tests are not exhaustive and may not include all the enzymes associated with the various types of MPS. For instance, MPS III and MPS VI are not routinely included in many newborn screening panels, depending on the region and the specific tests available.

If there is a concern about the possibility of other types of MPS, especially given your child's existing conditions (autism and nystagmus), it would be prudent to consult with a geneticist or a metabolic specialist. They can provide a comprehensive evaluation and may recommend further testing. This could include:
1. Enzyme Assays: Specific tests to measure the activity of enzymes associated with different types of MPS. This can help identify deficiencies in enzymes that are not covered in the newborn screening.

2. Genetic Testing: This can identify mutations in the genes responsible for various types of MPS. Genetic testing can provide a definitive diagnosis and help rule out other types of MPS.

3. Urine GAG Analysis: This test measures the levels of GAGs in the urine, which can be elevated in individuals with MPS. While not specific to any one type, it can indicate the presence of a mucopolysaccharidosis.

4. Clinical Evaluation: A thorough clinical assessment by a specialist can help identify any signs or symptoms that may suggest a specific type of MPS.

It is essential to discuss your concerns with your child's healthcare provider, who can guide you on the appropriate next steps based on your child's medical history and current symptoms. Early diagnosis and intervention can significantly impact the management and outcomes of MPS, so it is important to pursue further evaluation if there are any lingering concerns.