Implementation of second-tier tests in newborn screening for the detection of vitamin B12 related acquired and genetic disorders: results on 258,637 newborns

BACKGROUND

Alteration of vitamin B₁₂ metabolism can be genetic or acquired, and can result in anemia, failure to thrive, developmental regression and even irreversible neurologic damage. Therefore, early diagnosis and intervention is critical. Most of the neonatal cases with acquired vitamin B₁₂ deficiency have been detected by clinical symptoms and only few of them trough NBS programs. We aim to assess the usefulness of the second-tier test: methylmalonic acid (MMA), methylcitric acid (MCA) and homocysteine (Hcys) in our newborn screening program and explore the implications on the detection of cobalamin (vitamin B₁₂) related disorders, both genetic and acquired conditions.

METHODS

A screening strategy using the usual primary markers followed by the analysis of MMA, MCA and Hcys as second tier-test in the first dried blood spot (DBS) was developed and evaluated.

RESULTS

During the period 2015-2018 a total of 258,637 newborns were screened resulting in 130 newborns with acquired vitamin B₁₂ deficiency (incidence 1:1989), 19 with genetic disorders (incidence 1:13,613) and 13 were false positive. No false negatives were notified. Concerning the second-tier test, the percentage of cases with MMA above the cut-off levels, both for genetic and acquired conditions was very similar (58% and 60%, respectively). Interestingly, the percentage of cases with increased levels of Hcys was higher in acquired conditions than in genetic disorders (87% and 47%, respectively). In contrast, MCA was high only in 5% of the acquired conditions versus in 53% of the genetic disorders, and it was always very high in all patients with propionic acidemia.

CONCLUSIONS

When screening for methylmalonic acidemia and homocystinuria, differential diagnosis with acquired vitamin B₁₂ deficiency should be done. The results of our strategy support the inclusion of this acquired condition in the NBS programs, as it is easily detectable and allows the adoption of corrective measures to avoid the consequences of its deficiency.

Leigh syndrome associated with TRMU gene mutations

tRNA 5-methylaminomethyl-2-thiouridylate methyltransferase (TRMU) deficiency causes an early onset potentially reversible acute liver failure, so far reported in less than 30 patients. We describe two new unrelated patients with an acute liver failure and a neuroimaging compatible with Leigh syndrome (LS) due to TRMU deficiency, a combination not previously reported. Our report enlarges the phenotypical spectrum of TRMU disease.

Efficacy and safety of bortezomib in refractory lupus nephritis: a single-center experience

BACKGROUND AND OBJECTIVES

Resistant lupus nephritis (LN) has been associated with the persistence of long-lived plasma cells. Preliminary studies identified bortezomib as a potential treatment option for patients with refractory LN. The aim of this study was to analyze the efficacy and safety of bortezomib in the treatment of severe refractory LN.

METHODS

This retrospective study included 12 female patients diagnosed for the first time with class IV or IV/V LN with acute or rapidly progressive kidney injury (n = 11) and/or severe nephrotic syndrome (n = 1) who showed resistance to induction therapy with cyclophosphamide, steroids, mycophenolate, and rituximab, and were treated with either intravenous or subcutaneous bortezomib plus intravenous dexamethasone.

RESULTS

All patients with acute or rapidly progressive kidney injury showed a significant reduction in both biochemical and immunological activity after a mean of 6 (minimum 5, maximum 7) weekly cycles of bortezomib regimen, with a significant increase in C3 levels and a significant decrease of anti-ds DNA antibody titers, Systemic Lupus Erythematosus Disease Activity Index score, serum creatinine, and proteinuria. One patient (8.3%) achieved a complete response, and 10 patients (83.4%) achieved a partial response. During follow-up, all these patients maintained partial responses under treatment with mycophenolate and low-dose glucocorticoids. The patient with refractory nephrotic syndrome showed a partial response but relapsed 11 months after the end of bortezomib treatment and was resistant to treatment. A significant decrease in serum IgG levels after initiation of bortezomib treatment was observed in all patients, five of them (41.6%) showed hypogammaglobulinemia (<500 mg/dl), but no patient suffered from opportunistic infections; in only two patients (16.6%) hypogammaglobulinemia persisted at the end of follow-up. Two patients (16.6%) suffered from sensory neuropathy, which led to bortezomib treatment discontinuation.

CONCLUSIONS

Bortezomib may be an effective option for refractory LN, but close monitoring must be performed for possible adverse events such as peripheral neuropathy and hypogammaglobulinemia.

Mesangial C4d Deposits in Early IgA Nephropathy

BACKGROUND AND OBJECTIVES

The prognostic value of mesangial C4d deposits in IgA nephropathy has been analyzed in patients with reduced GFR but has not been analyzed in those with normal kidney function. The main objective of the study was to analyze the prognostic value of C4d deposits and association with response to treatment in patients with IgA nephropathy and normal GFR.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This retrospective cohort study included 190 patients with idiopathic IgA nephropathy diagnosed by kidney biopsy between 1988 and 2005. The patients had GFR≥80 ml/min per 1.73 m2 at the time of diagnosis, and they had a paraffin-embedded kidney biopsy with eight glomeruli available.

RESULTS

In total, 170 (89%) and 20 (11%) patients were >18 and <18 years old, respectively; median (interquartile range) follow-up was 15 (12-22) years. Mesangial C4d deposit prevalence was 20% (38 of 190). At diagnosis, C4d-positive versus -negative patients had higher protein-to-creatinine ratio (median [interquartile range]: 1.94 g/g [0.9-3.1] versus 1.45 g/g [0.9-2.2]; P=0.04). During follow-up, C4d-positive patients showed a higher number of nephritic flares (median [range]: 1.4 [0-5] versus 0.9 [0-2]; P=0.04), had a higher protein-to-creatinine ratio (median [interquartile range]: 1.32 g/g [0.7-1.7] versus 0.89 g/g [0.1-1.3]; P<0.01), were more prone to receive repeated treatment with corticosteroids (45% versus 24%; P<0.01), and showed a larger reduction in eGFR (-1.6 versus -0.8 ml/min per 1.73 m2 per year; P=0.04). Furthermore, the presence of mesangial C4d deposits was an independent predictor of long-term kidney survival.

CONCLUSIONS

C4d deposits may be one of the earliest poor prognostic variables available for patients with idiopathic IgA nephropathy and normal kidney function at the time of diagnosis. However, Cd4 deposits alone are not associated with the response to angiotensin blockers or corticosteroid treatment.

Realized heritability of tonic immobility in White Leghorn hens: a replicated single generation test

Fearfulness was measured as latency to recover from induced tonic immobility using White Leghorn hens from a population originated by crossing three different strains selected for egg number and egg weight. Realized heritability was calculated in a single generation selection experiment with eight replicates, each consisting of 76 40-wk-old females from which 21% were selected for decreased tonic immobility duration. A randomly selected control population was maintained for each replicate. Separately from this experiment, fear differences between ages and sexes were investigated at 1, 2, 4, 8, 12, 16, 20, 24, 28, and 32 wk. The realized heritability (.32 +/- .10) indicates that induced tonic immobility should respond to selection. It was numerically higher than the estimate calculated by half-sib analysis of variance in the base population (.18 +/- .07); the logarithmic transformation did not yield higher heritability estimates. Crossing effects were evaluated in two different crossbreds, i.e., Leghorn x Castellana and Buff Prat x White Prat, which suggested important negative heterotic effects for this fear-related trait (-31% and -54%, respectively). Significant (P < .05) quadratic and cubic variation between 1 and 32 wk of age was obtained in females and males, respectively; the involvement of these age effects make it difficult to generalize about realized heritability for tonic immobility. Tonic immobility increased from 32 to 72 wk. Differences between the sexes were apparent, males showing longer tonic immobility durations than females except in the postjuvenile period before sexual maturity, suggesting a relationship between this trait and hormonal changes.