A novel p.Gly417Valfs*12 mutation in the MTTP gene causing abetalipoproteinemia: Presentation of the first patient in Mexico and analysis of the previously reported cases.

BACKGROUND: Our aims were to describe the first Mexican patient with abetalipoproteinemia and to perform a comparative analysis of biochemical, clinical, and genetic characteristics of 100 cases reported in the literature. METHODS: We performed biochemical and molecular screenings in a Mexican girl with extremely low lipid levels and in her family. Further, we integrated and evaluated the characteristics of the cases with abetalipoproteinemia described in the literature. RESULTS: Our patient is a six-year-old girl who presented vomiting, chronic diarrhea, failure to thrive, malabsorption, acanthocytosis, anemia, transaminases elevation, and extremely low lipid levels. MTTP gene sequencing revealed homozygosity for a novel mutation p.Gly417Valfs*12 (G deletion c.1250). With the analysis of the reported cases, 60 clinical features (14 classical and 46 non-classical) were observed, being the most common acanthocytosis (57.5%), malabsorption (43.7%), and diarrhea (42.5%); 48.8% of the patients presented only classic clinical features, while the remaining 51.2% developed secondary effects due to a fat-soluble vitamin deficiency. An odds ratio analysis disclosed that patients diagnosed after 10 years of age have an increased risk for presenting clinical complications (OR = 18.0; 95% CI 6.0-54.1, p < 0.0001). A great diversity of mutations in MTTP has been observed (n = 76, being the most common p.G865X and p.N139_E140) and some of them with possible residual activity. CONCLUSION: The first Mexican patient with abetalipoproteinemia presents a novel MTTP mutation p.Gly417Valfs*12. Three factors that could modulate the phenotype in abetalipoproteinemia were identified: age at diagnosis, treatment, and the causal mutation.

Acanthocytosis and the c.680 A>G Mutation in the PANK2 Gene: A Study Enrolling a Cohort of PKAN Patients from the Dominican Republic.

Pantothenate Kinase-Associated Neurodegeneration (PKAN) is a form of Neurodegeneration with Brain Iron Accumulation (NBIA) associated with mutations in the pantothenate kinase 2 gene (PANK2). Pantothenate kinases catalyze the rate-limiting step of coenzyme A synthesis and Pank2 is the only pantothenate kinase isoform in humans that is localized to mitochondria. Acanthocytosis, the occurrence of spiculated erythrocytes, is observed in about 10% of the PKAN patients. Therefore PKAN is also classified together with other rare neurodegenerative diseases like Chorea Acanthocytosis (ChAc) and McLeod syndrome (MLS) into the Neuroacanthocytosis (NA) syndromes. It has not been investigated yet whether acanthocytosis in PKAN is associated with a specific subset of Pank2 mutations. In this study, we analyzed acanthocytosis of a cohort of 25 PKAN patients from the Dominican Republic that are homozygous for the c.680 A>G mutation in the PANK2 gene as compared to control donors that are heterozygous or wild-type with respect to this mutation. 3D modeling of this mutation indicated that the replacement of a tyrosine by a cysteine at position 227 in Pank2 disrupts a polar interaction within the A domain of the enzyme. Mean acanthocyte count was elevated in the cohort of patients, however, acanthocytosis varied among the patients with nearly half of them showing high (>20%) or elevated acanthocytosis and the rest showing mild (6-10%) or no (<6%) acanthocytosis. Heterozygous control donors revealed a tendency to mild acanthocytosis. Based on the insight that Pank2 is a normal constituent of red blood cells and de novo biosynthesis of coenzyme A is likely to take place in the erythrocyte cytosol we propose a hypothetical model that accounts for the variability in the occurrence of acanthocytic cells in PKAN.

Identification of a novel mutation of MTP gene in a patient with abetalipoproteinemia.

Abetalipoproteinemia (ABL), or Bassen-Kornzweig syndrome, is a rare autosomal recessive disorder of lipoprotein metabolism, characterized by fat malabsorption, hypocholesterolemia retinitis pigmentosa, progressive neuropathy and acanthocytosis from early infancy. We describe the clinical and molecular characterization of a 6-month-old infant born of consanguineous, apparently healthy parents from Iran. The patient was hospitalized because of failure to thrive, greasy stool and vomiting. The patient's serum lipid profile, the clinical phenotype and the duodenal histology suggested the clinical diagnosis of ABL. The MTP gene analysis by direct sequencing revealed a novel homozygous mutation (c.1586 A > G-H529R). The parents were heterozygotes for the same mutation and interestingly the father showed a lipid profile characterized by a slight reduction of total and LDL-cholesterol plasma levels.