Differential Diagnosis
The following signs and symptoms suggest a diagnosis other than hypokalemic periodic paralysis (hypoPP): • Associated sensory symptoms, including pain or tenderness • Sensory loss could suggest polyneuropathy such as Guillain-Barr syndrome. • Pain could suggest myositis; however, some individuals with hypoPP report paralytic episodes as painful. • Urinary retention or constipation, which may be observed in other causes of acute or subacute paralysis, but can occur rarely in hypoPP • Associated symptoms that suggest myasthenia or involvement of the neuromuscular junction, including: • Ptosis • Diplopia • Dysphagia • Dysarthria • Alteration or loss of consciousness • Abnormal movement • History of fever days before an attack, which could suggest poliomyelitis or other virus-caused paralysis • History of back pain days before an attack, which could suggest acute transverse myelitis • History of tick bite, which could suggest tick paralysis HypoPP is the most common cause of periodic paralysis. The four major differential diagnoses are normokalemic potassium-sensitive periodic paralysis (normoPP), hyperkalemic periodic paralysis (hyperPP), thyrotoxic periodic paralysis (TPP), and Andersen-Tawil syndrome (ATS) . Table 3. The Different Categories of Periodic Paralyses (PP) with Membrane Excitability Disorder and Associated Findings
HypoPP | NormoPP | HyperPP | TPP1 |
|---|
Main clinical features | Weakness episodes lasting hrs to days w/concomitant hypokalemia | Weakness episodes lasting hrs to days w/concomitant normokalemia | Weakness episodes lasting mins to hrs w/concomitant normo- or hyperkalemia |
Age at first attacks | Late in 1st decade or in 2nd decade | Late in 1st decade or in 2nd decade | 1st years of life |
Main triggers | Rest after exercise, carbohydrate rich meal, salt intake, stress, cold | Rest after exercise, carbohydrate rich meal, salt intake, stress, cold | Cold, rest after exercise, stress, fatigue, alcohol, hunger, changes in activity level, potassium in food, specific foods |
EMG: myotonic discharges | No | Some | Some |
EMG tests | Late decrement w/LET(Pattern IV, V) | Late decrement w/LET(Pattern IV, V) | Pattern IV, V |
Extramuscular expression | None | None | None |
Prevention of paralysis attacks | ACZ, DCP | ACZ, DCP | ACZ, DCP |
Source: GeneReviews — "Hypokalemic Periodic Paralysis"
