Research Notes: Hypotonia

Muscle Nerve. 1993 Jul.
Muscle carnitine deficiency and lipid storage myopathy in patients with mitochondrial myopathy.
Campos Y, Huertas R, Bautista J, Gutierrez E, Aparicio M, Lorenzo G, Segura D, Villanueva M, Cabello A, Alesso L, et al.
Centro de Investigacion, Hospital 12 de Octubre, Madrid, Spain.

Abnormal carnitine distribution in muscle was found in 22 of 77 patients (29%), with mitochondrial myopathy. Furthermore, total (TC) and free (FC) carnitine levels in muscle were lower in patients than in controls (P < 0.01). Muscle long-chain acylcarnitines (LCAC) were significantly increased in these patients (P < 0.01). Muscle carnitine deficiency was found in 31.5% of patients with lipid storage myopathy (LSM) and in 25.6% of patients with ragged-red fibers (RRF). Therefore, carnitine deficiency can be found in patients with mitochondrial myopathy even in the absence of LSM. Muscle levels of TC and FC were lower in patients with respiratory chain defects than in those with normal respiratory chain (P < 0.01). In contrast, LCAC levels were significantly increased (P < 0.05). Carnitine levels did not differ significantly, among patients with different respiratory-chain defects. Consequently, these patients, owing to their biochemical block, reduce progressively the muscle carnitine pool and subsequent LCAC rise, due to long-chain fatty acid (LCFA) accumulation.

Muscle Nerve. 1993 Feb.
Plasma carnitine insufficiency and effectiveness of L-carnitine therapy in patients with mitochondrial myopathy.
Campos Y, Huertas R, Lorenzo G, Bautista J, Gutierrez E, Aparicio M, Alesso L, Arenas J.
Centro de Investigacion, Hospital 12 de Octubre, Madrid, Spain.

Plasma carnitine "insufficiency," (plasma esterified carnitine to free carnitine ratio above 0.25) was found in 21 of 48 (43.8%) patients with mitochondrial myopathy, of whom 4 also showed both total and free carnitine deficiencies in plasma. In addition, plasma levels of SCAC and LCAC were higher in patients with mitochondrial myopathy than in controls (P < 0.001 and P < 0.01, respectively). Patients diagnosed as having plasma carnitine insufficiency or deficiency were treated with L-carnitine (50-200 mg/kg per day in four daily doses). Muscle weakness improved in 19 of 20 patients, failure to thrive in 4 of 8, encephalopathy in 1 of 9, and cardiomyopathy in 8 of 8 patients. Plasma carnitine "insufficiency" provides an additional clue to the diagnosis of mitochondrial myopathy and an indication for L-carnitine therapy.

Am J Dis Child. 1987 Jun.
Plasma carnitine deficiency. Clinical observations in 51 pediatric patients.
Winter SC, Szabo-Aczel S, Curry CJ, Hutchinson HT, Hogue R, Shug A.
We studied the clinical spectrum associated with secondary plasma carnitine deficiency in 51 pediatric patients. Forty-three patients had total plasma carnitine values below 20 mumol/L and an additional eight patients had total values above 20 mumol/L but had low free plasma carnitine levels. The clinical presentation in the patients with total plasma carnitine deficiency included hypotonia (34 of 43), failure to thrive (27 of 43), recurrent infections (27 of 43), encephalopathy (six of 43), nonketotic hypoglycemia (seven of 43), and cardiomyopathy (nine of 43). Of the eight patients with low free and elevated esterified carnitine levels, the signs and symptoms at presentation included hypotonia (six of eight), recurrent infections (six of eight), failure to thrive (six of eight), encephalopathy (three of eight), nonketotic hypoglycemia (one of eight), and cardiomyopathy (one of eight). All patients were treated with L-carnitine. Treatment time varied from one month to 24 months (average, four months). A subjective improvement in muscle tone was seen in 24 of 38 patients, 22 of 33 patients showed acceleration of incremental growth, and infection frequency appeared to decrease in 18 of 33 patients. After therapy, the echocardiograms of all patients with cardiomyopathy normalized. There were no further hypoglycemic episodes. Of the nine patients with encephalopathy, eight showed improvement in their mental status. Three patients died of complications of their primary disorder. In our experience, secondary plasma carnitine deficiency is a common pediatric finding. The presence of failure to thrive, recurrent infections, hypotonia, encephalopathy, cardiomyopathy, or nonketotic hypoglycemia requires investigation of carnitine status.