Episodes of exercise-induced dark urine and myalgia in LGMD 2I

Mutations in the fukutin-related protein gene FKRP (MIM *606596) cause a form of congenital muscular dystrophy (MDC1C) and also limb girdle muscular dystrophy type 2I (LGMD2I). Exercise-induced myoglobinuria, frequently occurring in metabolic myopathies, has been described in Becker muscular dystrophy and in a few cases of LGMD.

To describe that episodes with myoglobinuria, often associated with exercise-induced myalgia, may be common and a presenting symptom in patients with LGMD2I.

Data on episodes of suspected myoglobinuria and myalgia were collected from the patient records on 14 patients with a diagnosis of LGMDI.

Five LGMD2I patients reported recurrent episodes of dark urine and myalgia after exercise, and in three of them, this was the only symptom for several years.

We conclude that episodes compatible with exercise-induced myoglobinuria may be frequent in LGMD2I.