Thomsen disease is an autosomal dominant, chloride channelopathy that presents with intermittent muscular stiffness, usually at rest, and generalized but mild muscular hypertrophy. This is a rare condition with a prevalence of 1:23,000 with only two unrelated individuals reported locally. Here we present a summary of clinical, EMG and laboratory findings of three Filipino siblings aged twenty-two, nineteen and seventeen, two of which were genetically confirmed to have T310M missense mutation, who came to our clinic for difficulty in ambulation, intermittent cramping and muscle hypertrophy.