MCT8 Deficiency in Two Brothers With a Novel Deletion Mutation in SLC16A2

Area of Science:

• Genetics
• Endocrinology
• Neurology

Background:

• Monocarboxylate transporter 8 (MCT8) deficiency, or Allan-Herndon-Dudley syndrome, is a rare X-linked disorder caused by mutations in the SLC16A2 gene.
• It disrupts thyroid hormone (TH) transport, leading to varied symptoms like neurodevelopmental delay and hypotonia.

Purpose of the Study:

• To report the diagnostic journey of two brothers with MCT8 deficiency.
• To emphasize the clinical heterogeneity and diagnostic challenges associated with this rare condition.

Main Methods:

• Case report detailing the clinical presentation and diagnostic process for two affected siblings.
• Genetic testing to identify SLC16A2 mutations.
• Analysis of thyroid hormone profiles.

Main Results:

• Both brothers presented with severe motor deficits but experienced diagnostic delays.
• Genetic testing revealed a novel SLC16A2 mutation (960_995del) in both patients.
• One patient's thyroid hormone profile was atypical, lacking the expected T3 elevation.

Conclusions:

• This case underscores the significant clinical heterogeneity of MCT8 deficiency.
• Increased awareness is crucial for timely diagnosis of Allan-Herndon-Dudley syndrome.
• Atypical thyroid hormone profiles can occur despite classic clinical features.