Neonatal carnitine palmitoyltransferase-2 deficiency: a case presenting with myopathy

Infantile onset carnitine palmitoyltransferase 2 deficiency: Cortical polymicrogyria, schizencephaly, and gray matter heterotopias in an adolescent with normal development

OBJECTIVE

To report an adolescent with infantile-onset carnitine palmitoyltransferase 2 (CPT2) deficiency and cerebral malformations and to review the occurrence of brain malformations in CPT2 deficiency. The patient presented clinically at age 5 months with dehydration and hepatomegaly. He also has an unrelated condition, X-linked nephrogenic diabetes insipidus. He had recurrent rhabdomyolysis but normal psychomotor development. At age 17 years, he developed spontaneous focal seizures. Cerebral magnetic resonance imaging revealed extensive left temporo-parieto-occipital polymicrogyria, white matter heterotopias, and schizencephaly. Neuronal migration defects were previously reported in lethal neonatal CPT2 deficiency but not in later-onset forms.

DESIGN AND METHODS

We searched PubMed, Google Scholar, and the bibliographies of the articles found by these searches, for cerebral malformations in CPT2 deficiency. All antenatal, neonatal, infantile, and adult-onset cases were included. Exclusion criteria included insufficient information about age of clinical onset and lack of confirmation of CPT2 deficiency by enzymatic assay or genetic testing. For each report, we noted the presence of cerebral malformations on brain imaging or pathological examination.

RESULTS

Of 26 neonatal-onset CPT2-deficient patients who met the inclusion criteria, brain malformations were reported in 16 (61.5%). In 19 infantile-onset cases, brain malformations were not reported, but only 3 of the 19 reports (15.8%) include brain imaging or neuropathology data. In 276 adult-onset cases, no brain malformations were reported.

CONCLUSION

To the best of our knowledge, this is the first report of cerebral malformations in an infantile onset CPT2-deficient patient. Brain imaging should be considered in patients with CPTII deficiency and neurological manifestations, even in those with later clinical onset.

Phospholipids: Identification and Implication in Muscle Pathophysiology

Phospholipids (PLs) are amphiphilic molecules that were essential for life to become cellular. PLs have not only a key role in compartmentation as they are the main components of membrane, but they are also involved in cell signaling, cell metabolism, and even cell pathophysiology. Considered for a long time to simply be structural elements of membranes, phospholipids are increasingly being viewed as sensors of their environment and regulators of many metabolic processes. After presenting their main characteristics, we expose the increasing methods of PL detection and identification that help to understand their key role in life processes. Interest and importance of PL homeostasis is growing as pathogenic variants in genes involved in PL biosynthesis and/or remodeling are linked to human diseases. We here review diseases that involve deregulation of PL homeostasis and present a predominantly muscular phenotype.

Neonatal carnitine palmitoyltransferase II deficiency associated with Dandy-Walker syndrome and sudden death

Neonatal onset of carnitine palmitoyltransferase II (CPT II) deficiency is an autosomal recessive, often lethal disorder of the mitochondrial beta-oxidation of long-chain fatty acids. It is a rare multiorgan disease which includes hypoketotic hypoglycemia, severe hepatomuscular symptoms, cardiac abnormalities, seizures and lethargy, as well as dysmorphic features. Until now, only 22 affected families have been described in the literature. An increasing number of mutations are being identified in the CPT2 gene, with a distinct genotype-phenotype correlation in most cases. Herein we report a new case of neonatal CPT II deficiency associated with Dandy-Walker syndrome and sudden death at 13 days of life. CPT II deficiency was suggested by acylcarnitine analysis of dried-blood on filter paper in the expanded newborn screening. Genetic analysis of the CPT2 gene identified the presence of a previously described mutation in homozygosity (c.534_558del25bpinsT). All lethal neonatal CPT II deficiency patients previously described presented severe symptoms during the first week of life, although this was not the case in our patient, who remained stable and without apparent vital risk during the first 11 days of life. The introduction of tandem mass spectrometry to newborn screening has substantially improved our ability to detect metabolic diseases in the newborn period. This case illustrates the value of expanded newborn screening in a neonate with an unusual clinical presentation, combining hydrocephalus and sudden death, that might not commonly lead to the suspicion of an inborn error of metabolism.

Severe infantile carnitine palmitoyltransferase II deficiency in 19-week fetal sibs

Antenatal presentation of carnitine palmitoyltransferase type II deficiency due to mutations in the CPT2 gene has been rarely reported. We report an Ashkenazi Jewish family with 3 terminated pregnancies for multicystic kidneys and/or hydrocephalus. Fetal autopsy after termination of the couple's 4th pregnancy (sib 2) showed renal parenchyma replaced by cysts that appeared to increase in diameter toward the medulla. Fetopsy after termination of the 7th pregnancy (sib 3) revealed micrognathia; hypospadias; cystic renal dysplasia; hepatosteatosis; and lipid accumulation in the renal tubular epithelium, myocardium, and skeletal muscle. Microvascular proliferative changes and focal polymicrogyria were seen in the brain. A beta-oxidative enzyme deficiency was suspected. CPT2 gene analysis showed a homozygous complex haplotype for the F448L mutation associated with a c.del1238_1239AG (p.Q413fs) truncating mutation in exon 4. Carnitine palmitoyltransferase type II deficiency should be included in the differential diagnosis in fetuses of Ashkenazi origin with multicystic kidneys and unusual cerebral findings.

Carnitine palmitoyltransferase II deficiency: a clinical, biochemical, and molecular review

Congenital deficiency of carnitine palmitoyltransferase (CPT) II has been known for at least 30 years now, and its phenotypic variability remains fascinating. Three distinct clinical entities have been described, the adult, the infantile, and the perinatal, all with an autosomal recessive inheritance pattern. The adult CPT II clinical phenotype is somewhat benign and requires additional external triggers such as high-intensity exercise before the predominantly myopathic symptoms are elicited. The perinatal and infantile forms involve multiple organ systems. The perinatal disease is the most severe form and is invariably fatal. The introduction of mass spectrometry to analyze blood acylcarnitine profiles has revolutionized the diagnosis of fatty acid oxidation disorders including CPT II deficiency. Its use in expanded neonatal screening programs has made presymptomatic diagnosis a reality. An increasing number of mutations are being identified in the CPT II gene with a distinct genotype-phenotype correlation in most cases. However, clinical variability in some patients suggests additional genetic or environmental modifiers. Herein, we present a new case of lethal perinatal CPT II deficiency with a rare missense mutation, R296Q (907G>A) associated with a previously described 25-bp deletion on the second allele. We review the clinical features, the diagnostic protocol including expanded neonatal screening, the treatment, and the biochemical and molecular basis of CPT II deficiency.

Detection of neonatal carnitine palmitoyltransferase II deficiency by expanded newborn screening with tandem mass spectrometry

The introduction of tandem mass spectrometry to newborn screening has substantially expanded our ability to diagnose metabolic diseases in the newborn period. We report the first case of neonatal carnitine palmitoyltransferase deficiency II detected by expanded newborn screening with tandem mass spectrometry. The neonate presented with dysmorphic facial features, structural malformations, renal failure, seizures, and cardiac arrythmias and died on the third day of life. This experience illustrates the importance of expanded newborn screening to avoid missing a metabolic diagnosis in early infantile death.

Muscular carnitine palmitoyltransferase II deficiency in infancy

An 8-month-old female presented with febrile myoglobinuria. The activity of carnitine palmitoyltransferase (CPT) II was decreased to 16% of the control mean, and the oxidation of the long-chain fatty acids was reduced to 25% of the mean in the fibroblasts. Homozygosity for the common mutation, S113L, was identified in the CPT II gene. Residual CPT II activity of more than 10% of the mean and homozygosity for the common mutation S113L are usually associated with a milder reduction of long-chain fatty acid oxidation to about 80% of the control and with a later age of clinical onset. The early clinical presentation in the present patient is unique and was associated with a marked impairment of long-chain fatty acid oxidation, possibly because of other genetic factors. CPT II deficiency should be included in the differential diagnosis of isolated myoglobinuria in infancy.

Carnitine palmitoyltransferase deficiencies

Carnitine palmitoyltransferase (CPT) deficiencies are common disorders of mitochondrial fatty acid oxidation. The CPT system is made up of two separate proteins located in the outer- (CPT1) and inner- (CPT2) mitochondrial membranes. While CPT2 is a ubiquitous protein, two tissue-specific CPT1 isoforms-the so-called "liver" (L) and "muscle" (M) CPT1s-have been shown to exist. Amino acid and cDNA nucleotide sequences have been identified for all of these proteins. L-CPT1 deficiency (13 families reported) presents as recurrent attacks of fasting hypoketotic hypoglycemia. Two L-CPT1 mutations have been reported to date. M-CPT1 deficiency has not been hitherto identified. CPT2 deficiency has several clinical presentations. The "benign" adult form (more than 150 families reported) is characterized by episodes of rhabdomyolysis triggered by prolonged exercise. The prevalent S113L mutation is found in about 50% of mutant alleles. The infantile-type CPT2 deficiency (10 families reported) presents as severe attacks of hypoketotic hypoglycemia, occasionally associated with cardiac damage commonly responsible for sudden death before 1 year of age. In addition to these symptoms, features of brain and kidney dysorganogenesis are frequently seen in the neonatal-onset CPT2 deficiency (13 families reported), almost always lethal during the first month of life. More than 25 CPT2 mutations (private missense or truncating mutations) have hitherto been detected. Treatment is based upon avoidance of fasting and/or exercise, a low-fat diet enriched with medium chain triglycerides and carnitine ("severe" CPT2 deficiency). Prenatal diagnosis may be offered for pregnancies at a 1/4 risk of infantile/severe-type CPT2 deficiency.

Genetic disorders of carnitine metabolism and their nutritional management

Carnitine functions as a substrate for a family of enzymes, carnitine acyltransferases, involved in acyl-coenzyme A metabolism and as a carrier for long-chain fatty acids into mitochondria. Carnitine biosynthesis and/or dietary carnitine fulfill the body's requirement for carnitine. To date, a genetic disorder of carnitine biosynthesis has not been described. A genetic defect in the high-affinity plasma membrane carnitine-carrier(in) leads to renal carnitine wasting and primary carnitine deficiency. Myopathic carnitine deficiency could be due to an increase in efflux moderated by the carnitine-carrier(out). Defects in the carnitine transport system for fatty acids in mitochondria have been described and are being examined at the molecular and pathophysiological levels. the nutritional management of these disorders includes a high-carbohydrate, low-fat diet and avoidance of those events that promote fatty acid oxidation, such as fasting, prolonged exercise, and cold. Large-dose carnitine treatment is effective in systemic carnitine deficiency.