What is HyperKPP and what are its symptoms?
The periodic paralyses are caused by abnormalities in the ion channels (especially the sodium, calcium and potassium channels) of the muscle membrane. The ion channels control the movement of sodium, chloride, potassium and calcium across the cell membrane and from one cell compartment to another. This movement of ions produces the electrical ‘spark’ which allows our muscles to move. Hyperkalemic periodic paralysis is caused by a flaw in a sodium channel in the muscle membrane. This flaw makes the person with HyperKPP extremely sensitive to increases in serum potassium that wouldn’t bother the average person. Anyone can be made weak by a drastic increase in serum potassium, but the person with HyperKPP gets weak with even a slight elevation in potassium level, and patients with HyperKPP may become profoundly paralyzed while their potassium levels remain well within normal limits, even when their potassium is on the lower end of normal. Weakness most commonly affects the muscles of the
Hyperkalemic Periodic Paralysis is a rare inherited disorder which causes episodes of paralysis or weakness. It was only identified as a separate disorder in 1955. Hyperkalemic periodic paralysis causes attacks of muscle weakness and (in some patients) muscle stiffness. The attacks of weakness are usually brief (many attacks may only last a few minutes) but they may include muscle pain and an irregular heartbeat. Patients may experience brief episodes of localized weakness in a hand, foot, jaw or limbs or they may experience generalized paralysis. These episodes often occur during rest after exercise, and they may occur on awakening in the morning. Attacks may develop quite rapidly, causing unexpected falls. The muscle stiffness (medical term ‘myotonia’) may come and go or it may be more or less constant. In myotonia the muscle fibers are slow to relax after contraction. Some patients are very athletic in appearance due to the myotonia, but appearances can be deceiving as these well-de
