McArdle’s disease: A differential diagnosis of idiopathic toe walking

Abstract

Idiopathic toe walking (ITW) is a pathological gait pattern in which children walk on their tip toes with no orthopedic or neurological reason. Physiological characteristics of the gastrocnemius muscles, the Achilles tendon, and the foot of toe walkers differ from subjects with a plantigrade walking pattern. McArdle's disease is characterized by the inability to break down muscle glycogen. It is an autosomal-recessive condition, characterized by low exercise tolerance, muscular atrophy at the shoulder girdle, episodes of myoglobinuria after vigorous physical activities and the occurrence of the second wind phenomenon. The aim of this review is to present the case studies of two subjects who were originally diagnosed as idiopathic toe walkers, but were then found to have McArdle's disease. This review will describe some physical characteristics that distinguish McArdle´s disease from Idiopathic toe walkers.

A 6-Year-Old Girl with Recurrent Rhabdomyolysis

“…In this case, an accurate previous medical history and follow-up with an estimated incidence of 1/100,000 [6,[11][12][13].…”

“…Presentation varies from early childhood to adult age, with some rare cases of late-onset disease (>60 years-old) [12]. Only 4% of cases are diagnosed before the age of ten, because affected children are often considered to be just less active [9,11,13].…”

“…Usually symptoms include weakness, myalgia, cramps and exercise intolerance, with stiffness of exercising muscles, relieved by rest [8][9][10][11][12]. A classical symptom is the "second wind phenomenon".…”

“…Some minutes after the onset of the typical exercise-induced myalgia, with the continuation of the physical activity, the patients report a decrease in the level of effort, pain and fatigue. This phenomenon is explained by the shift of the metabolic pathway used to generate energy, using fatty acids to provide enough energy to continue the exercise [5,8,9,11].…”

“…Neurological evaluation is usually normal between crises, but proximal muscle weakness and wasting occur in approximately 35% of patients over 40 years of age [9]. A hypertrophied gastrocnemius and an atrophy of the girdle muscles are secondary signs of this disease [11].…”