Application of multiplex ligation-dependent probe amplification, and identification of a heterozygous Alu-associated deletion and a uniparental disomy of chromosome 1 in two patients with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency.

Mitochondrial 3-hydroxy-3-methylglutaryl-CoA lyase (HMGCL) deficiency is an autosomal recessive disorder affecting the leucine catabolic pathway and ketone body synthesis, and is clinically characterized by metabolic crises with hypoketotic hypoglycemia, metabolic acidosis and hyperammonemia. In the present study, we initially used PCR with genomic followed by direct sequencing to investigate the molecular genetic basis of HMGCL deficiency in two patients clinically diagnosed with the condition. Although we identified a mutation in each patient, the inheritance patterns of these mutations were not consistent with disease causation. Therefore, we investigated HMGCL using multiplex ligation-dependent probe amplification (MLPA) to determine the copy numbers of all exons. A heterozygous deletion that included exons 2-4 was identified in one of the patients. MLPA revealed that the other patient had two copies for all HMGCL exons. Paternal uniparental isodisomy of chromosome 1 was confirmed in this patient by microarray analysis. These findings indicate that MLPA is useful for the identification of genomic aberrations and mutations other than small-scale nucleotide alterations. To the best of our knowledge, this is the first study describing HMGCL deficiency caused by uniparental disomy.

A case of a 6-year-old girl with anti-neutrophil cytoplasmic autoantibody-negative pauci-immune crescentic glomerulonephritis.

A 6-year-old girl was admitted to our hospital with proteinuria, hematuria, skin rash and joint pain of the lower limbs. Due to rapid progression of renal insufficiency, hemodialysis and peritoneal dialysis were performed. She was diagnosed with rapidly progressive glomerulonephritis. Kidney biopsy showed severe crescent formation (50% of glomeruli) and no deposition of any immunoglobulins or complements. Serologically, anti-neutrophil cytoplasmic autoantibody (ANCA) was negative not only by ELISA against proteinase-3 and myeloperoxidase-ANCA but also by indirect immunofluorescent assay against cytoplasmic and perinuclear ANCA. Anti-glomerular basement membrane antibody was also negative. In the acute phase, proinflammatory cytokines such as soluble tumor necrosis factor receptor 1 (sTNFR1), soluble interleukin (IL)-2 receptor (sIL2R), IL-6 and chemokine IL-8 were elevated. The patient was diagnosed with ANCA-negative pauci-immune crescentic glomerulonephritis (CrGN). Intensive treatment with methylprednisolone pulse therapy, plasma exchange, and multiple drug therapy including prednisolone and cyclophosphamide resulted in histopathological improvement and complete remission of proteinuria. There was a possibility that sTNFR1, sIL2R, IL-6 and IL-8 might be involved in the initiation and progression of ANCA-negative pauci-immune CrGN, and to remove and suppress these cytokines might be an effective way to treat ANCA-negative pauci-immune CrGN.