Duplication 6q24: More Than Just Diabetes

Area of Science:

• Genetics
• Endocrinology
• Developmental Biology

Background:

• Chromosome 6q24-related transient neonatal diabetes mellitus (TNDM) is a genetic disorder characterized by intrauterine growth restriction, low birth weight, and neonatal hyperglycemia.
• This condition arises from overexpression of the 6q24 imprinted region, typically due to duplication, uniparental disomy, or abnormal methylation.
• Current diagnostic methods focus on methylation patterns at 6q24 but may miss broader chromosomal abnormalities.

Observation:

• A female infant presented with neonatal hyperglycemia, later diagnosed with a paternally inherited duplication at 6q24.
• At 15 months, she exhibited developmental delay and balance issues.
• Microarray analysis revealed an extended 14 Mb duplication from 6q24 to 6q25.2, indicating duplication 6q syndrome.

Findings:

• The patient's initial diagnosis of TNDM due to 6q24 duplication was refined by identifying a larger 6q24-6q25.2 duplication.
• This larger duplication was associated with significant developmental delays, suggesting a more complex genetic etiology than initially presumed.
• Targeted methylation-specific multiplex ligation-dependent probe amplification (MLPA) analysis was key in identifying the specific duplication.

Implications:

• This case underscores the necessity of comprehensive genetic evaluation beyond standard methylation analysis for 6q24-related TNDM.
• Early and accurate diagnosis of larger chromosomal duplications is vital for appropriate management and intervention.
• Prompt identification of genetic causes can significantly improve developmental trajectories and long-term health outcomes for affected children.