Balkan Journal of Medical Genetics

A CASE OF GLYCOGEN STORAGE DISEASE TYPE 1a MIMICKING FAMILIAL CHYLOMICRONEMIA SYNDROME
Olgac A1,*, Okur İ2, Biberoğlu G2, Ezgü FS2, Tümer L2
*Corresponding Author: Dr. Asburce Olgac, Department of Pediatric Metabolism, University of Health Sciences, Dr. Sami Ulus Maternity and Child Health, Training and Research Hospital, Ankara, Turkey. Tel.: +90-312-305-600. Fax: +90-312-317-03-53. E-mail: mabolgac@yahoo.com
page: 103

INTRODUCTION

Glycogen storage disease type 1a (GSD1a) (Von Gierke disease) is an autosomal recessively inherited inborn error of metabolism caused by a mutation in the G6PC gene, which encodes the catalytic subunit of glu-cose-6- phosphatase-α (G6Pase-α) enzyme. This enzyme plays a role in the final step of gluconeogenesis and glyco-genolysis by hydrolyzing G6P to glucose and phosphate. Due to the deficient activity of this enzyme, excessive accumulation of glycogen occurs in the liver, kidney, skeletal muscles and intestinal mucosa. As glucose homeostasis cannot be maintained during fasting, life-threatening hypoglycemia episodes may be seen [1]. Hyperlipidemia is the indicator of poor metabolic control in GSD1a [2]. Patients with variable levels of triglycerides (TGs) have been reported in the literature. We present a case of GSD1a that was referred due to severe hypertriglyceridemia (HTG) mimicking familial chylomicronemia syndrome (FCS). Written consent was obtained from parents for the preparation and publication of this manuscript. Patients and Methods. The case being reported here is a female patient who is the offspring of a nonconsanguineous marriage. She was born at term after an uncomplicated pregnancy, and hypoglycemia was detected once in the second postnatal hour, that was easily resolved with oral dextrose and did not recur. She was fed exclusively with breast-milk with frequent feeds, and her weight gain was adequate afterwards. When she was 2 months old, she had an episode of irritability, fever and vomiting. She was admitted to an external clinic, where laboratory analyses including complete blood count, biochemistry and acute phase reactants were performed that showed normal results. Urinalysis was negative. Since the medical staff noticed her blood to be lipemic during blood draw, the lipid profile was checked showing severely elevated triglyceride (TG) levels (18,000.0 mg/dL, normal range: 2.0-150.0 mg/dL). Heparinized dextrose infusion was initiated, and she was referred to our clinic with a pre diagnosis of FCS. Upon admission, she was in good condition. Her weight, height and head circumference were within normal centiles. Physical examination revealed a rounded doll’s face, abdominal distension, and hepatomegaly (liver was 8 cm palpable at the mid-clavicular margin). The spleen was not palpable. Lipemia was noticed (Figure-1). Laboratory analyses showed elevated TG (10,000.0 mg/dL), total cholesterol: 927.0 mg/dL (normal range: 5.0-120.0 mg/dL), and lactate: 6.0 mg/dL (normal range: 0.2.0-2.0 mg/dL). Low-density lipoprotein (LDL) levels could not be evaluated due to high levels of TGs. Other biochemical analyses including kidney and liver function tests, uric acid, amilase, lipase and blood-gas analysis were within normal ranges. Due to the initial diagnosis of familial hyperlipidemia, hydrolyzed formula containing 50.0% medium-chain triglycerides (MCTs) and heparin with dextrose infusion was continued. Glucose infusion rate was increased due to hypoglycemia (47.0 mg/dL). Insulin level was checked during hypoglycemia and was found to be low. Urine ketone levels were positive. Metabolic tests including acylcarnitinites, plasma and urine amino acids, and biotinidase level were inconclusive. Highly increased lactic, 3-hydroxybutiric and acetoacetic acids were detected in urine organic acid analysis. Urine was checked for the presence reducing substance, that was found to be negative. Triglyceride levels decreased gradually to 1000.0 mg/dL and heparin infusion was terminated. Total cholesterol (TC) levels fell to within reference ranges. Abdominal ultra-sonography revealed increased diffuse echogenity of the liver. Due to hypoglycemia and ketonuria, a gluconeogenesis disorder was suspected. In the context of clinical and laboratory findings, GSD1a was the most probable diagnosis. Molecular genetic analysis of the G6PC gene showed a homozygous missense R83C mutation that was previously reported to be pathogenic. Frequent feedings with formula containing MCTs was continued and TG levels ranged within 300.0-400.0 mg/dL despite compliance to diet. The patient is now 6 years old and severe TG elevation has not recurred.

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