Broadening the Spectrum of SLC22A5 Phenotype: Primary Carnitine Deficiency Presenting with Focal Myoclonus

Maymunah Khries; Albert Lim; Dipayan Mitra; Mark Anderson; Jan Bengtsson; Ann Bowron; Elizabeth Harris; Jessica Blickwedel; Karen Wood; Anna P Basu

doi:10.1177/2329048X231184183

Broadening the Spectrum of SLC22A5 Phenotype: Primary Carnitine Deficiency Presenting with Focal Myoclonus

Child Neurol Open. 2023 Jul 17:10:2329048X231184183. doi: 10.1177/2329048X231184183. eCollection 2023 Jan-Dec.

Authors

Maymunah Khries¹, Albert Lim¹, Dipayan Mitra², Mark Anderson³, Jan Bengtsson⁴, Ann Bowron⁵, Elizabeth Harris⁶, Jessica Blickwedel¹, Karen Wood¹, Anna P Basu^{1

7}

Affiliations

¹ Paediatric Neurology, Great North Children's Hospital, Newcastle upon Tyne, UK.
² Neuroradiology, Great North Children's Hospital, Newcastle upon Tyne, UK.
³ Paediatrics, Great North Children's Hospital, Newcastle upon Tyne, UK.
⁴ Paediatric Intensive Care Unit, Great North Children's Hospital, Newcastle upon Tyne, UK.
⁵ Metabolic Biochemistry, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK.
⁶ Northern Genetics Service, Centre for Life, Newcastle upon Tyne, UK.
⁷ Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, UK.

Abstract

Primary carnitine deficiency (PCD) is caused by pathogenic variants of the SLC22A5 gene, which encodes a transmembrane protein that functions as a high affinity carnitine transporter. Carnitine is essential for the transport of acyl-CoA, produced from fatty acids, into the mitochondria where they are oxidised to produce energy. We present the case history of an 8-year-old boy who presented with fever, lethargy, focal rhythmic (3 Hz) left wrist twitching, and severe encephalopathy. MRI brain showed basal ganglia involvement. Metabolic investigations revealed low serum carnitine; whole genome sequencing confirmed compound heterozygous SLC22A5 mutations. With carnitine replacement, intensive care support, and neurorehabilitation, he made a remarkable recovery, regaining independent breathing, speech, mobility, and hand use. Seizure presentation in PCD is rare and presentation with sustained focal myoclonus has not been previously reported. This case expands the known phenotype of PCD. Prompt carnitine replacement is imperative.

Keywords: focal myoclonus; genotype phenotype; primary carnitine deficiency.

Publication types

Case Reports