Glycogenosis type 7

Overview

An inherited metabolic disorder where there is a deficiency of phosphofructokinase-1 in the muscle and a partial deficiency in red blood cells which prevents glucose being converted to energy during exercise.

Symptoms

* Easily fatigued * Stiff muscles after exercise * Reticulocytosis * Reduced red cell life span * Reduced red cell phosphofructokinase activity * Destruction of red blood cells * Muscle pain following exercise * Muscle cramps * Increased blood uric acid level * Gout * Recurrent jaundice

Causes

Almost all glycogen storage diseases (Types I through V and Type VII) are transmitted as autosomal recessive traits. The transmission mode of Type VI is unknown; Type VIII may be an X-linked trait. The most common glycogen storage disease is Type I — von Gierke’s, or hepatorenal glycogen storage disease — which results from a deficiency of the liver enzyme glucose-6-phosphatase. This enzyme converts glucose-6-phosphate into free glucose and is necessary for the release of stored glycogen and glucose into the bloodstream, to relieve hypoglycemia. Infants may die of acidosis before age 2; if they survive past this age, with proper treatment, they may grow normally and live to adulthood, with only minimal hepatomegaly. However, there’s a danger of adenomatous liver nodules, which may be premalignant.

Prognosis

good with treatment

Treatment

For Type I, treatment aims to maintain glucose homeostasis and prevent secondary consequences of hypoglycemia through frequent feedings and constant nocturnal nasogastric (NG) drip with Polycose, dextrose, or Vivonex. Treatment includes a low-fat diet, with normal amounts of protein and calories; carbohydrates should contain glucose or glucose polymers only. Therapy for Type III includes frequent feedings and a high-protein diet. Type IV requires a high-protein, high-calorie diet; bed rest; diuretics; sodium restriction; and paracentesis, if necessary, to relieve ascites. Types V and VII require no treatment except avoidance of strenuous exercise. No treatment is necessary for Types VI and VIII; no effective treatment exists for Type II.