Clinical Presentation and Positive Outcome of Two Siblings with Holocarboxylase Synthetase Deficiency Caused by a Homozygous L216R Mutation

Abstract

Purpose The L216R mutation, seen in individuals of Polynesian descent, is considered one of the most severe mutations associated with holocarboxylase synthetase (HLCS) deficiency and is regarded as being unresponsive to biotin. This report describes the presentation and outcome in two surviving siblings, homozygous for this highly lethal mutation.

Methods and results Both cases had perinatal head imaging findings of brain hemorrhage and subependymal cysts. Both had metabolic decompensation within 24 h after birth consisting of metabolic acidosis, lactic acidosis, and thrombocytopenia. Biochemical profiles were consistent with HLCS deficiency, and genetic analysis confirmed homozygosity for the L216R mutation. After resolution of neonatal metabolic crisis, dosing of biotin was titrated on an outpatient basis to primarily control dermatitis. The eldest is currently on 1.2 g of oral biotin daily, well above any dose previously reported to treat HLCS deficiency. To date, neither patient has required hospital readmission for acute metabolic decompensation. At the age of 7, the eldest child is, to our knowledge, the oldest patient ever described in the literature who is homozygous for the L216R mutation. She has mild intellectual disability.

Conclusion This report contrasts previous reports of poor outcomes and neonatal deaths in homozygous L216R patients. We also provide data on the potential upper tolerable limit of biotin. These cases suggest that the outcome of HCLS deficiency due to a homozygous L216R mutation, when diagnosed and treated early with high-level neonatal care and biotin, may not be as severe as previously reported.

Competing interests: None declared

Appendices

Synopsis

This report provides documentation about the natural history and potential positive outcomes in two patients with HLCS deficiency due a homozygous L216R mutation when treated with high-dose oral biotin.

Compliance with Ethics Guidelines

Conflict of Interest

Thomas Slavin, Syed Zaidi, Charles Neal, Brenda Nishikawa, and Laurie Seaver declare that they have no conflict of interest.

Contributions by Authors

Thomas Slavin and Laurie Seaver were the metabolic clinicians involved in the care of the siblings and primary writers of the report. Charles Neal provided neonatal care and assisted with report editing and the discussion of IVIG therapy. Syed Zaidi helped care for Case 2 as a neonate and assisted with the background research. Brenda Nishikawa was the children’s pediatrician and helped edit this report for overall accuracy.

Informed Consent

Patients described in this case report were treated with standard medical care. Proper consent was obtained for inclusion of the patients in this case report. This report was reviewed by Hawai‘i Pacific Health and was found to meet the definition of a case report and is in compliance with applicable research and patient privacy regulations. Additional informed consent was obtained for all patients for whom identifying information is included in this report.