# Diagnostic Challenges in the Myopathic Variant of Carnitine Palmitoyltransferase II Deficiency: A Case Report

## TL;DR

A 10-year-old boy with a rare metabolic disorder showed exercise-induced muscle damage, and genetic testing identified a new mutation linked to the condition.

## Contribution

The paper reports a novel compound heterozygous pathogenic variant in CPT2 associated with myopathic carnitine palmitoyltransferase II deficiency.

## Key findings

- The patient's condition improved with hydration, glucose, carnitine, and alkalinization.
- Genetic testing identified a compound heterozygous pathogenic variant c.338C>T and a variant of unknown significance c.729_731del.
- The patient experienced three further attacks over four years despite dietary and lifestyle interventions.

## Abstract

Carnitine palmitoyltransferase II deficiency is a rare metabolic disorder affecting the mitochondrial oxidation of fatty acids.

We present a case of the myopathic form in a 10-year-old Bahraini male following an initial presentation of exercise-induced rhabdomyolysis and transaminitis. There was no consanguinity or findings suggestive of an underlying inborn metabolic disorder. Tandem mass spectrometry on dried blood spots showed no abnormal acyl-carnitines profile. The condition improved with hyperhydration, high glucose intake, carnitine, and alkalinization. Genetic testing revealed a compound heterozygous pathogenic variant c.338C>T (p.Ser113Leu) and a variant of unknown significance c.729_731del (p.Leu244del). The patient was kept on a high carbohydrate and low-fat diet with medium chain triglycerides supplementation and advised to avoid long fasting periods and strenuous exercise. Within the four years of follow-up, he had three further attacks.

Exercise-induced myalgia or rhabdomyolysis should raise the suspicion of inherited metabolic disorders. Metabolic investigations should be taken during the acute illness, and an acylcarnitines profile should preferably be performed in the serum.