Novel Homozygous MTHFR Variant Causing Homocystinuria: Subtle Phenotypic Clues in Carriers

Area of Science:

• Genetics
• Metabolic Disorders
• Biochemistry

Background:

• Homocystinuria is a rare inherited metabolic disorder.
• It results from defects in methionine metabolism, leading to elevated homocysteine levels.
• Early diagnosis and management are crucial to prevent severe complications.

Observation:

• A 17-year-old male presented with tall stature, intellectual disability, and skeletal abnormalities.
• He had significantly elevated plasma homocysteine levels, unresponsive to pyridoxine therapy.
• Genetic analysis identified a novel homozygous missense variant (p.Lys625Thr) in the MTHFR gene.

Findings:

• The patient's MTHFR gene variant suggests a specific molecular basis for his homocystinuria.
• The father, a carrier, showed subtle phenotypic traits and elevated homocysteine, indicating potential variable expressivity.
• Pyridoxine unresponsiveness and the novel mutation necessitate alternative treatment strategies.

Implications:

• This case emphasizes the importance of genetic testing for accurate diagnosis of homocystinuria.
• Individualized treatment approaches, including low-methionine diet, vitamin supplementation, and betaine therapy, are critical.
• Comprehensive family screening is essential to identify carriers and manage potential health risks.