[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Carnitine palmitoyltransferase II (CPT-II) deficiency [Conditions](https://durgical.com/en/conditions/) · [Metabolism: fatty acids and ketones](https://durgical.com/en/conditions/) # Carnitine palmitoyltransferase II (CPT-II) deficiency An inherited disorder that stops muscle burning fat; long exercise or fasting can break down muscle fibres and damage the kidneys. Updated 2026-11-01 ## Structures involved Tap one to see what it is and open it in 3D. - [Vastus lateralis](https://durgical.com/en/anatomy/vastus-lateralis-muscle/) - [Gastrocnemius (inner head)](https://durgical.com/en/anatomy/medial-head-of-gastrocnemius/) - [Kidneys](https://durgical.com/en/anatomy/kidney/) - [Liver](https://durgical.com/en/anatomy/liver/) - [Rectus femoris](https://durgical.com/en/anatomy/rectus-femoris-muscle/) ## In biochemistry - [Creatine kinase (CK) and CK-MB as lab tests](https://durgical.com/en/biochemistry/topics/creatine-kinase-and-ck-mb-as-lab-tests/) - [Carnitine palmitoyltransferase I (CPT-I)](https://durgical.com/en/biochemistry/enzymes/carnitine-palmitoyltransferase-i/) - [Carnitine (L-carnitine)](https://durgical.com/en/biochemistry/molecules/carnitine/) - [Carnitine shuttle](https://durgical.com/en/biochemistry/topics/carnitine-shuttle/) - [Exercise metabolism](https://durgical.com/en/biochemistry/topics/exercise-metabolism/) ## What it is An autosomal recessive defect of the CPT-II enzyme (CPT2 gene), the last step of the carnitine shuttle. The adult myopathic form is the most common inherited fat-related cause of recurrent rhabdomyolysis. ## Who gets it Rare. The myopathic form is the most frequent, with more than 300 reported cases; the lethal neonatal and infantile hepatocardiomuscular forms are known in a few dozen families. ## Causes - Variants in both copies of CPT2; p.Ser113Leu is common in the myopathic form - Autosomal recessive inheritance ## Risk factors - Prolonged exercise (more than short intense effort) - Fasting or a very low-carbohydrate diet - Cold, fever, infections and stress - Some medicines (for example, valproic acid) and general anaesthesia ## Pathophysiology CPT-II puts CoA back on the acyl group inside the mitochondrion. If it fails, long-chain fatty acids cannot enter β-oxidation and build up as acylcarnitines. Muscle relies on fat during prolonged exercise and fasting; without it the muscle runs out of energy, fibres break down (rhabdomyolysis) and release myoglobin, which can block and injure the renal tubules. ## Classification - Myopathic (adolescent or adult): episodes of muscle pain and myoglobinuria - Severe infantile hepatocardiomuscular: hypoglycaemia, [liver](https://durgical.com/en/anatomy/liver/) failure, cardiomyopathy - Lethal neonatal: malformations, liver failure and arrhythmias ## Symptoms and signs - Muscle pain and stiffness after long exercise - Muscle weakness - Dark, tea- or cola-coloured urine - Normal strength between episodes ## Red flags - Dark urine with muscle pain (myoglobinuria) - Reduced urine output after an episode - Very high CK - Respiratory weakness ## Diagnosis **Clinical** Suspected with repeated rhabdomyolysis triggered by prolonged exercise, fasting, cold or fever, with normal muscle between crises. **Tests** Very high CK and myoglobinuria during a crisis; creatinine and potassium to watch the [kidney](https://durgical.com/en/anatomy/kidney/); acylcarnitine profile with high C16 and C18:1; CPT2 genetic testing or enzyme activity in muscle or fibroblasts. **Imaging** Usually not needed; muscle MRI can show oedema during a crisis. ## Treatment **Acute** In rhabdomyolysis: generous intravenous fluids and glucose, watching kidney function and potassium **Lifestyle** High-carbohydrate diet, frequent meals and no fasting **Lifestyle** Plan exercise with breaks and carbohydrate; medium-chain oils as advised by the care team **Follow-up** Follow-up of CK and kidney function, and review of medicines and anaesthesia ## Complications - Acute kidney injury from myoglobin - Hyperkalaemia and arrhythmias - Respiratory failure in severe crises ## Prognosis Good in the myopathic form if triggers are avoided; the infantile and neonatal forms have high mortality. ## Prevention - Avoiding triggers and family genetic counselling. ## Test yourself Think of the answer, then tap the question to see it. ## What typically triggers crises in myopathic CPT-II deficiency? Prolonged exercise, fasting, cold or fever, when muscle relies on fat. ## Why can the kidney be damaged in CPT-II deficiency? Rhabdomyolysis releases myoglobin, which is filtered and injures the renal tubules. ## Which acylcarnitines are raised in CPT-II deficiency? Long-chain ones, mainly C16 and C18:1. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/conditions/carnitine-palmitoyltransferase-ii-deficiency/) ## Related conditions - [Acute kidney injury](https://durgical.com/en/conditions/acute-kidney-injury/) - [Primary carnitine deficiency](https://durgical.com/en/conditions/primary-carnitine-deficiency/) - [Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency](https://durgical.com/en/conditions/medium-chain-acyl-coa-dehydrogenase-deficiency/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [Carnitine palmitoyltransferase II deficiency: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/carnitine-palmitoyltransferase-ii-deficiency/) (MedlinePlus, US National Library of Medicine, 2026); [CPT2 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/cpt2/) (MedlinePlus, US National Library of Medicine, 2026); [Carnitine shuttle](https://reactome.org/PathwayBrowser/#/R-HSA-200425) (Reactome, 2026). [← All conditions](https://durgical.com/en/conditions/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/conditions/carnitine-palmitoyltransferase-ii-deficiency/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/carnitine-palmitoyltransferase-ii-deficiency/