Systemic primary carnitine deficiency (CDSP) is an inherited disorder where the body is unable to use certain fats for energy. Symptoms typically start between three months and two years of age. During times of illness or fasting, children affected with CDSP can have episodes of low blood sugar, poor feeding, irritability, and weakness. These episodes could lead to coma and sudden death. Affected individuals often have weak muscles, including weak and enlarged heart muscles that lead to heart failure. The liver also often becomes enlarged. The severity of symptoms is quite variable. Some individuals may only experience muscle fatigue in adulthood and some may have no symptoms at all. Intellect is not affected by CDSP. Treatment with lifelong carnitine supplementation and avoiding long periods without food generally eliminate the risk for complications of CDSP. CDSP is caused by pathogenic variants in the SLC22A5 gene.