Riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency with unknown genetic defect

Area of Science:

• Biochemistry
• Genetics
• Metabolic Disorders

Background:

• Multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare inherited metabolic disorder affecting fatty acid metabolism.
• Mutations in ETFA, ETFB, or ETFDH genes are typically associated with MADD.
• Riboflavin is a known treatment that improves outcomes for ETFDH-related MADD.

Observation:

• A 20-year-old male presented with progressive motor difficulties suggestive of MADD.
• Muscle biopsy and acylcarnitine profile supported a diagnosis of MADD.
• Standard genetic testing of ETFA, ETFB, and ETFDH exons and intron-exon boundaries did not reveal mutations.

Findings:

• Despite the absence of detectable mutations in common MADD genes, riboflavin treatment led to significant improvement in the patient's motor functions.
• This suggests that MADD can arise from genetic defects not detectable by standard exon/intron-exon boundary sequencing, such as promoter or deep intronic mutations, or unknown genetic factors.

Implications:

• The study indicates that MADD cases lacking typical genetic mutations may still respond to riboflavin therapy.
• It underscores the need for extended molecular studies, including cDNA analysis and pedigree studies, to identify novel genetic causes of MADD.
• Early diagnosis and consideration of riboflavin treatment are crucial for managing MADD, even in genetically atypical presentations.