Bachmann–Bupp syndrome

Lore & Background

The discovery of Bachmann–Bupp syndrome began when a medical geneticist encountered a 3-year-old girl with complete hair loss, an enlarged head, low muscle tone, and developmental delays. Genetic testing revealed a mutation in the ODC1 gene, but initially no one could identify the condition. The syndrome was later named after the researchers involved in its identification.

Symptoms include hair present at birth that is lost in the first few weeks, absent or sparse eyebrows, nonspecific dysmorphic features, motor and speech delays, hypotonia, and behavioral issues such as ADHD, autism, and aggressive tendencies. Growth parameters often show larger head circumference and macrosomia at birth, which may resolve with age.

As of November 2022, fewer than 30 individuals have been reported worldwide. Diagnosis is confirmed through molecular genetic testing, either gene-targeted sequencing of ODC1 or comprehensive genomic testing when the phenotype overlaps with other disorders.

Reader's Guide

Bachmann–Bupp syndrome is significant as a recently identified ultra-rare disorder that highlights the role of ODC1 mutations in human disease. The condition demonstrates a clear gain-of-function mechanism: mutations prevent ubiquitin-independent proteasomal degradation of ODC, leading to accumulation of the enzyme and increased conversion of ornithine to putrescine. This biochemical pathway provides a target for potential treatment.

An exploratory treatment using difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, is currently being studied by the FDA. A case study of a young patient who began treatment at 4 years and 8 months old showed increased hair growth, improved muscle tone, and increased myelination of white matter in the brain, with no observed side effects. This suggests that DFMO may improve neurological function in affected individuals.

The syndrome's legacy lies in demonstrating how a single gene defect can produce a complex, multisystem disorder, and in opening avenues for targeted therapy. Ongoing surveillance is recommended, including monitoring growth, nutrition, development, and mobility, as no standard cure exists.

Did You Know?

• Bachmann–Bupp syndrome is caused by 3' end mutations of the ODC1 gene that prevent ubiquitin-independent proteasomal degradation of the ODC enzyme.
• Hair is present at birth but is lost in the first few weeks of life; eyebrows are absent or sparse.
• As of November 2022, fewer than 30 individuals with BABS had been reported in medical literature.
• An exploratory treatment using DFMO, an irreversible inhibitor of ODC, showed increased hair growth and improved neurological function in a case study.