We report a young wheelchair-dependent patient with an unclear proximal
myopathy and a heterozygous, de-novo Cav1.1-R1239G mutation suggesting
hypokalemic periodic paralysis (
HypoPP). Sonography showed a loss of the pennate pattern indicative of an
edema, whereas fatty degeneration was excluded. Within 7 days of
therapy with
spironolactone,
potassium and
physical therapy, muscle strength almost completely normalized, a normal pennate pattern appeared and the
edema was markedly reduced. She learned to walk without aid and to do sports and has continued to do so for 11 years until now. Over the years, we tested serum
potassium values, muscle strength, muscle
edema and muscular
sodium content by 1.5 T, 3 T and 7 T 1H and 23Na magnetic resonance imaging. No fatty muscle degeneration developed. Muscular
edema-like changes only occurred when she was pregnant and was set to reduced
therapy. Because of the ability to do sports again, her mobility was further increased. Our observational study on this single patient may suggest that: (1) muscle imaging and molecular genetics are important diagnostic tools, (2) weakness in periodic
paralysis may be reversible, and (3) continued adequate
therapy may preserve muscle structure and strength on a longterm, whereas weakness due to fatty degeneration could be considered progressive and irreversible. Although
HypoPP is a
rare disease, it should be included in differential diagnosis not only if there is paroxysmal weakness, but also in cases of
myopathy of unknown origin.