Differential Diagnosis
In addition to the allelic disorders described in , other conditions with periodic paralysis or with hyperkalemia to consider when making the diagnosis of hyperkalemic periodic paralysis (hyperPP) are discussed below. Adult onset of clinical manifestations points to other diagnoses such as the Andersen-Tawil syndrome or secondary acquired forms of hyperPP. The following signs and symptoms suggest a diagnosis other than hyperPP: • 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 hyperPP report paralytic episodes as painful and show symptoms of fibromyalgia . • Urinary retention or constipation, which may be observed in other causes of acute or subacute paralysis, but can occur rarely in hyperPP. (Bowel incontinence and bladder incontinence during attacks are reported in hyperPP.) • Associated symptoms that suggest myasthenia or involvement of the neuromuscular junction, including: • Ptosis (Lid lag myotonia, which may mimic ptosis, may rarely be reported in hyperPP; see .) • Diplopia • Dysphagia (may rarely be reported in hyperPP; see .) • 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 or Guillain-Barr syndrome • History of tick bite, which could suggest tick paralysis The four major differential diagnoses of hyperPP are hypokalemic periodic paralysis (hypoPP), normokalemic potassium-sensitive periodic paralysis (normoPP), thyrotoxic periodic paralysis (TPP), and Andersen-Tawil syndrome (ATS) . HypoPP is the most common cause of periodic paralysis. Table 4. The Different Categories of Periodic Paralyses (PP) with Membrane Excitability Disorder and Associated Findings HypoPP
