J. Inherit. Metab. Dis. 28 (2005) 703–706
C SSIEM and Springer
DOI: 10.1007/s10545-005-0095-9
Biochemical characteristics and increased tetraglucoside excretion in patients with phosphorylase kinase deficiency E. MORAVA1,∗ , S. B. WORTMANN1 , H. ZWEERS VAN ESSEN2 , R. LIEBRAND VAN SAMBEEK3 , R. WEVERS3 and O. P. VAN DIGGELEN4 Radboud University Nijmegen Medical Centre, 1 Department of Pediatrics, 2 Department of Dietetics, 3 Laboratory of Neurology and Pediatrics, Nijmegen; 4 Erasmus University Medical Centre, Department of Clinical Genetics, Rotterdam, The Netherlands ∗
Correspondence: Radboud University Nijmegen Medical Centre, Department of Pediatrics, PO Box 9101, 6500 HB Nijmegen, The Netherlands. E-mail:
[email protected]
MS received 28.01.05
Accepted 26.04.05
Summary: Patients with glycogen storage disease type IXa present with infantile hepatomegaly and a specific growth pattern, and variable biochemical alterations in blood. We studied the clinical and biochemical characteristics including the urinary oligosaccharide excretion of seven unrelated children. The urinary tetraglucoside excretion was increased in four children, three of whom had persistently high cholesterol and triglyceride concentrations. We propose screening for urine tetraglucoside excretion and the measurement of serum cholesterol in patients with growth delay and/or hepatomegaly to assess a possible glycogenosis.
Phosphorylase kinase (PHK) is a regulatory enzyme in glycogen metabolism. Mutations in the gene encoding the α subunit of PHK (PHKA2) have been detected in patients with glycogen storage disease type IXa (McKusick 306000) (Chen 2001; Hendrickx et al 1995), formerly known as X-linked liver glycogenosis (XLG). The clinical presentation is characterized by infantile hepatomegaly and a specific growth pattern with initial growth retardation, a late growth spurt and complete catch-up growth (Schippers et al 2003). Clinical signs of hypoglycaemia are not common. The biochemical alterations in blood are variable and the urine oligosaccharide excretion is seldom evaluated. Most adult patients have no obvious clinical symptoms, only a slightly altered lipid profile. Owing to the variable severity of symptoms, and a frequent presentation of an isolated growth delay, the clinical diagnosis can be difficult. We have retrospectively analysed the clinical and biochemical findings, and consecutively evaluated the current clinical status, laboratory parameters and the urine oligosaccharide excretion in seven children to find characteristic markers for early diagnosis and follow-up.
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PATIENTS We studied 7 unrelated children, 5 boys and 2 girls (carriers with symptoms) with a positive family history for XLG and decreased PHK activity (Table 1). All children had hepatomegaly as the first clinical symptom at physical examination. Apart from patient 2 with an isolated hepatomegaly, and patient 4, found through family screening and treated with cornstarch since the neonatal period, all children had a significant growth delay (length below −2SD) with failure to thrive. Patient 3 required continuous night tube-feeding owing to recurrent infections, liver dysfunction and a worsening nutritional state. Five out of seven patients were treated with raw cornstarch supplementation from the time of the diagnosis. In one boy and one girl, a growth spurt was detected on treatment (length −1SDS) and two children have persistent hepatomegaly. All children studied have been diagnosed in the first two years of life. The PHK activity in erythrocytes was between 0.1 and 2.2 nmol/min per mg Hb in the boys and 3.4 and 4.1 nmol/min per mg Hb in the carrier girls (control range 4.8–16). Initially only three patients had an increased activity of liver enzymes (ASAT, ALAT) and high triglyceride (TG), cholesterol and lactic acid concentrations. Altogether, six patients had high cholesterol levels. Despite the rare occurrence of low serum glucose concentrations in GSD IXa patients according to the literature, sporadic hypoglycaemia was observed in two boys. No obvious correlation was found between the residual PHK activity and the clinical symptoms. The urinary oligosaccharide excretion was increased in four children, three of whom have persistently high cholesterol and TG levels. METHODS Urine oligosaccharide excretion was analysed by one-dimensional thin-layer chromatography (TLC) on silica gel plates using two independent runs of eluents and visualized by orcinol staining. Urine samples were first desalted with an Amberlite mixed-bed resin ion exchanger (Sigma A-5710; 250 mg/ml urine). Oligosaccharides were analysed by onedimensional TLC on silica gel 60 plates (Merck, Darmstadt, Germany, no. 5553). The amount of sample applied is dependent on age and creatinine concentration. TLC plates were developed in n-butanol–acetic acid–water (2:1:1, by vol) and in a second independent run in propanol–acetic acid–water (95:15:1, by vol). Oligosaccharides were visualized using orcinol staining (100 mg orcinol (BDH Laboratory Supplies, Poole, UK, no. 29418) in 100 ml acetone and 5 ml sulphuric acid). Plates were heated for 20 min at 90◦ C. A tetraglucoside standard was obtained from Sigma Aldrich (4-O-(4-O-[6-O-α-D-glucopyranosylα-D-glucopyranosyl]-α-D-glucopyranosyl)-D-glucopyranose; Sigma no. G8519; CAS no. 35399-15-6). A band was identified as tetraglucoside only when its mobility was equal to that of the model compound on both TLC plates (butanol and propanol systems). RESULTS AND DISCUSSION We found a variable spectrum of symptoms and biochemical abnormalities in our GSD IXa patients. Growth delay, hepatomegaly and increased cholesterol levels were the most common signs observed. No correlation was found between the severity of the clinical and
J. Inherit. Metab. Dis. 28 (2005)
b Cornstarch supplementation since c Continuous night tube-feeding
initial presentation birth
− − − − − − −
+ + + + − + +++
a At
0.1
0.1
Enzyme activity (nmol/min per mgHb) (reference 4.8–16) Elevated ASAT/ALATa Elevated serum cholesterola Elevated serum TGa Elevated lactatea Persistently elevated lactate, ASAT or ALAT Persistently elevated cholesterol and/or TG Current tetraglucoside excretion
Male + 10 − − − − − + −
Male + 3 + + + + 2× − +
2
Sex Family history (X-linked inheritance) Current age (years) Hypoglycemiaa Hepatomegalya Length
