Abetalipoproteinemia in an infant with severe clinical phenotype and a novel mutation.

Abetalipoproteinemia (ABL) is a rare autosomal disorder characterized by extremely low levels of plasma lipids and apolipoprotein B (apoB) with a variable phenotype. Mutations in the MTP gene encoding the microsomal triglyceride transfer protein (MTP) cause the disease. A five-month-old boy, born from consanguineous parents, with chronic diarrhea and severe malnutrition had extremely low plasma lipids and apoB levels suggesting the diagnosis of ABL. He was not responsive to treatment with low-fat diet and fat-soluble vitamins and died at 13 months of age with severe malnutrition. Analysis of the MTP gene showed that he was homozygous for a two nucleotide deletion in exon 4 (c.398-399delAA) expected to cause a frameshift in the mRNA leading to a premature termination codon. The normolipidemic proband's parents were found to be heterozygous for the mutation. This observation underscores that in some cases, ABL can be extremely severe from early post-natal life and poorly responsive to treatment.