Pregnancy and its management in women with GSD type III - a single centre experience

We present a review of our experience and pregnancy outcome in patients with GSD III managed by our centre. Between 1997 and 2010 there were 15 pregnancies in seven women with GSD III. Four women had GSD IIIb (nine pregnancies) and three GSD IIIa (six pregnancies). There was a successful outcome in all 15 pregnancies with delivery of 15 liveborn infants. Four infants were of low birthweight (<2nd centile) but all have developed normally apart from one with behavioural/psychiatric problems. Three women had pre-existing cardiomyopathy prior to pregnancy. One of these women had deterioration of her cardiomyopathy during pregnancy and again in the post-partum period. Women with GSD III do not seem to have any issues with fertility. Overall the outcome of pregnancy for both mother and child is good. Care needs to be taken to avoid maternal hypoglycemia which may be associated with intrauterine growth restriction and low birth weight. Cardiac function should be monitored carefully particularly in those with pre-existing cardiomyopathy.     

A distinct mitochondrial myopathy,lactic acidosis and sideroblastic anemia (MLASA) phenotype associates with YARS2 mutations

Nuclear‐encoded disorders of mitochondrial translation are clinically and genetically heterogeneous. Genetic causes include defects of mitochondrial aminoacyl‐tRNA synthetases, and factors required for initiation, elongation and termination of protein synthesis as well as ribosome recycling. We report on a new case of myopathy, lactic acidosis and sideroblastic anemia (MLASA) syndrome caused by defective mitochondrial tyrosyl aminoacylation. The patient presented at 1 year with anemia initially attributed to iron deficiency. Bone marrow aspirate at 5 years revealed ringed sideroblasts but transfusion dependency did not occur until 11 years. Other clinical features included lactic acidosis, poor weight gain, hypertrophic cardiomyopathy and severe myopathy leading to respiratory failure necessitating ventilatory support. Long‐range PCR excluded mitochondrial DNA rearrangements. Clinical diagnosis of MLASA prompted direct sequence analysis of the YARS2 gene encoding the mitochondrial tyrosyl‐tRNA synthetase, which revealed homozygosity for a known pathogenic mutation, c.156C>G;p.F52L. Comparison with four previously reported cases demonstrated remarkable clinical homogeneity. First line investigation of MLASA should include direct sequence analysis of YARS2 and PUS1 (encoding a tRNA modification factor) rather than muscle biopsy. Early genetic diagnosis is essential for counseling and to facilitate appropriate supportive therapy. Reasons for segregation of specific clinical phenotypes with particular mitochondrial aminoacyl tRNA‐synthetase defects remain unknown. © 2013 Wiley Periodicals, Inc.     

Outcome of adult patients with X-linked hypophosphatemia caused by <Emphasis Type="Italic">PHEX</Emphasis> gene mutations

X-linked hypophosphatemia (XLH) is the most common monogenic disorder causing hypophosphatemia. This case-note review documents the clinical features and the complications of treatment in 59 adults (19 male, 40 female) with XLH. XLH is associated with a large number of private mutations; 37 different mutations in the PHEX gene were identified in this cohort, 14 of which have not been previously reported. Orthopaedic involvement requiring surgical intervention (osteotomy) was frequent. Joint replacement and decompressive laminectomy were observed in those older than 40 years. Dental disease (63%), nephrocalcinosis (42%), and hearing impairment (14%) were also common. The rarity of the disease and the large number of variants make it difficult to discern specific genotype-phenotype relationships. A new treatment, an anti-FGF23 antibody, that may affect the natural history of the disease is currently being investigated in clinical trials.