Refining the phenotype associated with biallelic DNAJC21 mutations.

Inherited bone marrow failure syndromes (IBMFS) are caused by mutations in genes involved in genomic stability. Although they may be recognized by the association of typical clinical features, variable penetrance and expressivity are common, and clinical diagnosis is often challenging. DNAJC21, which is involved in ribosome biogenesis, was recently linked to bone marrow failure. However, the specific phenotype and natural history remain to be defined. We correlate molecular data, phenotype, and clinical history of 5 unreported affected children and all individuals reported in the literature. All patients present features consistent with IBMFS: bone marrow failure, growth retardation, failure to thrive, developmental delay, recurrent infections, and skin, teeth or hair abnormalities. Additional features present in some individuals include retinal abnormalities, pancreatic insufficiency, liver cirrhosis, skeletal abnormalities, congenital hip dysplasia, joint hypermobility, and cryptorchidism. We suggest that DNAJC21-related diseases constitute a distinct IBMFS, with features overlapping Shwachman-Diamond syndrome and Dyskeratosis congenita, and additional characteristics that are specific to DNAJC21 mutations. The full phenotypic spectrum, natural history, and optimal management will require more reports. Considering the aplastic anemia, the possible increased risk for leukemia, and the multisystemic features, we provide a checklist for clinical evaluation at diagnosis and regular follow-up.

An isotopic study of the effect of dietary carbohydrate on the metabolic fate of dietary leucine and phenylalanine.

The fate of dietary leucine and phenylalanine was studied in five healthy, young adult men, by using a dual, stable isotope-tracer infusion approach to estimate amino acid fluxes, splanchnic (Sp) uptake, and dietary of absorbed amino acid to the peripheral circulation. Subject received two, 4-h tracer infusions of [1-13C]leucine and [15N]phenylalanine infused through a feeding tube placed in the duodenum, and [5,5,5-2H3]leucine, [ring-2H5]phenylalanine, and [6,6-2H2]glucose infused simultaneously by vein. In one experiment subjects received an amino acid mixture (83 mg amino acid.kg-1.h-1) via the feeding tube and in the other experiment amino acids were supplied with carbohydrate (CHO) (167 mg.kg-1.h-1). Sp uptake of dietary leucine decreased with added dietary CHO (29% of ingested leucine for amino acids alone vs 20% with CHO; P < 0.05) but was not different for phenylalanine (P > 0.05). Addition of CHO decreased both release of leucine via protein breakdown and leucine oxidation and increased body leucine balance (P < 0.05).

Adaptation to high protein intakes, with particular reference to formula feeding and the healthy, term infant.

The purpose of this paper is to attempt to define the upper limit of the safe range of protein intake, with particular reference to the protein content of prepared fixed-formulas used for feeding healthy, term infants. For discussion purposes we use the current upper limit proposed by the U.S. Food and Drug Administration (FDA), namely, 4.5 g protein per 100 kcal, as our initial reference level. To help reach a conclusion, the concept and definitions of nutritional adaptation and accommodation are considered, followed by a brief review of selected studies in full-term infants fed varying levels of protein intake. Based on growth and blood biochemical data, principally plasma free amino acid levels, we conclude that the currently proposed FDA upper limit is probably too high. The available data support a recommendation for lowering the value to about 3.5 g of protein per 100 kcal. Concerns for renal solute load (RSL) may require a further, desirable refinement in the value proposed. Indeed RSL should perhaps serve as the primary basis for establishing a rational and safe upper limit for the protein content of prepared fixed-formula diets for the very young, healthy infant.

Secretory diarrhea with protein-losing enteropathy, enterocolitis cystica superficialis, intestinal lymphangiectasia, and congenital hepatic fibrosis: a new syndrome.

Four infants had noninfectious intractable diarrhea, vomiting, anasarca, hepatomegaly, hypoglycemia, and malnutrition within the first 3 months of life. Their parents originated from the same Northeastern part of Quebec, and consanguinity was found in two kindreds. Diarrhea was secretory in three infants (mean stool volume 87 ml/kg/day, Na+ 108 mEq/L, Cl- 85 mEq/L). Hypoalbuminemia (mean 2.0 gm/dl), present in all infants, appeared to be secondary to a protein-losing enteropathy, which was documented in two infants. Histologic examination of the upper small intestine showed only mild to moderate villous atrophy. The remarkable findings were those of cystic dilation of the crypts and acute inflammation of crypts and lamina propria, all of which were most prominent in the colon and terminal ileum; the changes were progressive over time. Mild lymphangiectasia was found in all of the patients. Congenital hepatic fibrosis, present in all, was associated in one patient with a nonfunctional multicystic kidney. Prolonged total parenteral nutrition, intravenously administered albumin, antisecretory agents, and antibiotics were unsuccessful in controlling the disease. Although a total colectomy was followed by a temporary decrease in stool output and normalization of serum albumin concentration in one infant, the patients died between 4 and 21 months of age.