The most frequent presenting symptoms are abdominal pain and tachycardia. The abdominal pain is typically severe, colicky, poorly localized, and often associated with pain in back and legs. Patients may also present with vomiting and constipation, but diarrhea is unusual. The onset of back and leg pain is characterized by severe pain and stiffness in back and thighs followed by loss of tendon reflexes and paralysis. Psychiatric symptoms are present, such as paranoid schizophrenia-like features but rarely psychosis and hallucinations. The acute attacks classically present with dark-red photosensitive urine (often called port-wine urine), but this is a nonspecific symptom. Physical examination often shows no abnormalities.