Familial phosphoglycerate kinase deficiency associated with rhabdomyolysis and acute renal failure: abnormality in mRNA splicing?

Familial phosphoglycerate kinase deficiency associated with rhabdomyolysis and acute renal failure: abnormality in mRNA splicing? Sir, Phosphoglycerate kinase (PGK) is a glycolytic enzyme encoded by a gene located on chromosome X [1]. The clinical appearance of PGK deficiency is often dominated by myopathy usually associated with rhabdomyolysis, myo-globinuria and acute renal failure [2]. Here we describe two new myopathic cases of familial PGK deficiency (father and daughter) where abnormalities in mRNA splicing are suspected. Cases. Following moderate exercise in a physical education class, a 17-year-old girl presented muscular fatigue, brown-coloured urine, high fever and general malaise. She had a history of repeated effort intolerance exacerbated in physical education classes. Upon admittance, she had: urea 370 mgudl, creatinine 6.5 mgudl, potassium 6.9 mEqul and creatine phosphokinase 25 000 IUul (normal:-190 IUul). After 13 days of oliguria and 10 haemodialysis sessions her renal function returned to normal. Four years previously, her father (36-year-old) presented a similar episode. During a mild respiratory infection combined with alcoholic consumption, he presented diffuse muscular pain. In our unit, the blood tests showed: urea 205 mgudl, creatinine 8 mgul, potassium 8 mEqul and creatine phospho-kinase 56 250 IUul. After 17 days of oliguria and nine haemodialysis sessions his renal function returned to normal. The presence of rhabdomyolysis complicated with acute renal failure in both father and daughter in the absence of an obvious cause prompted us to suspect a genetic defect. In muscle extracts from both patients, several glycolytic enzymes had normal activities, except for PGK which was decreased. The decrease was more pronounced in the daughter, with only 2% of normal activity (1200–1600 nmoluminumg protein). Total RNA was isolated from the muscle biopsies of both patients. Phosphoglycerate kinase cDNA was amplified by RT–PCR from the patients' mRNA and from that of an unaffected control. The PCR products were subcloned into plasmids and transfected into competent bacterial cells. Screening of the colonies containing the inserts showed that both the father and the daughter had not only normal size PGK mRNA, but also other species of higher and lower molecular weight compared with control. While 100% of the control colonies had normal size PGK cDNA (1300 bases; Figure 1A), only ;23% of the daughter's and ;14% of the father's PGK cDNA were of normal length (Figure 1B and C, respectively). These data strongly suggest that both patients have a defect at the PGK mRNA level, probably involving splicing. …