Common symptoms of Parkinson disease includes: Tremor, rigidity, bradykinesia, Cognitive dysfunction and dementia, psychosis and hallucinations, mood disorders including depression, anxiety, and apathy/abulia, sleep disturbances, fatigue, olfactory dysfunction, pain and autonomic dysfunction.

• The most common symptoms that a PD patient complains in his/her history are slowness of movement (bradykinesia), shaking hands while they are at rest (resting tremor) and muscle stiffness (rigidity).^[1]
• It is in the favor of PD diagnosis if the presenting symptoms start unilaterally and the severity of them remains higher in the side of onset.^[2]
• In their history they may mention some of the risk factors of Parkinson disease such as:
  • Family history^[3]
  • Depression^[4]
  • Exposure to pesticides^[3]
  • High consumption of dairy diet^[5]
  • Vitamin D deficiency^[6]
  • History of brain trauma^[7]
  • History of migraine with aura^[8]
  • History of anemia^[9]
  • Using of well water^[10]
  • Excess intake of iron and manganese^[11]
  • Obesity^[12]
  • Exposure to hydrocarbons solvents^[13]
  • Low muscle strength^[14]

The main clinical manifestations of Parkinson disease include tremor, rigidity and bradykinesia. Later in the course of the disease patient can have postural instability.^[15][2][2] Some studies suggest that there can be three clinical subtypes for Parkinson disease: Tremor dominant, akinetic-rigid and postural instability and gait difficulty^[16][17] but other studies demonstrate that clinical course of the disease can be variable and this subtypes can switch to each other through time.^[17][18]

• Tremor: Tremor is the most common symptom in Parkinson disease and can be the presenting sign in 70 to 80 percent of patients.^[19][1] This symptom starts unilaterally mostly in hand and then progress to the other side of the body. It can also involve legs, jaw, lips and tongue.^[20][21][22] PD tremor frequency is 3 to 7 Hz.^[20] There is a symptom called re-emergent tremor in some of the PD patients. It manifests by postural tremor that starts after several seconds and can make it difficult to differentiate PD from essential tremor.^[23][24]

• Rigidity: Rigidity in PD in very common and can be seen in 75 to 90 percent of patients.^[19][1][25] It commonly starts in the same side as the tremor. PD patients have increased resistance to passive movement of their joint and sometimes it’s known as cogwheel rigidity because of the ratchety pattern of resistance and relaxation. Some evidences suggest that superimposition of tremor on increased muscle tone creates this kind of rigidity.^[26][27]

• Bradykinesia: Bradykinesia or slowness of movement, is seen in 80 percent of PD patients.^[1]
• Postural instability: Gait and postural problems can be the main cause of disability in PD patients and commonly doesn’t response well to dopaminergic treatment.^[28][29]

• Cognitive dysfunction and dementia: Cognitive impairment can occur in the PD but in some ways it’s different from Alzheimer disease. Language dysfunction and memory deficit is less prominent while executive and visuospatial dysfunction is more prominent in PD.^{[30][31][32][33][34]} Parkinson’s diseases memory deficits are in the area of retrieval of learned information. Aphasia, apraxia and sever memory loss are uncommon in PD.^{[35][36][37][38]}

• Psychosis and hallucinations: Psychosis, especially visual hallucination occurs in PD patients who are under treatment.^[39][40][41] All of the antiparkinsonism drugs can cause this but dopamine agonists are the most common cause.^[42] Severity and prevalence of these hallucinations increase over time^[43] but can resolve when PD medications are discontinued.^[44]

• Mood disorders including depression, anxiety, and apathy/abulia:

1. Depression: Mild to moderate depression is very common in PD and can be seen in 50 percent of PD patients.^[45][46][47] these patients can present with anhedonia, sadness, guilt and feeling of worthlessness.^[48]
2. Anxiety: Anxiety, especially generalized anxiety disorder and social phobia is common in PD and can be seen in more than 30 percent of patients.^[45][49] Anxiety is usually combined by depression.^[50]
3. Apathy and abulia: Apathy and abulia are characterized by lack of motivation, speech, emotional and motor function. The pathophysiology behind this symptom is involvement of frontal lobe in PD patients.^[51][52]

• Sleep disturbances: Sleep disorders is seen in 55 to 80 percent of PD patients in early or late stages of the disease.^[53][54] approximately 40 percent of PD patients take medicine for sleep cause insomnia is as common as 60 percent in them.^[53][54][55] the most common cause of insomnia and frequent awakening during sleep include nocturia, cramp, pain, nightmares and tremor.^{[55][56][57][58][59]} another sleep disorder which can be seen in these patients is REM sleep behavior disorder (RBD), characterized by vigorous movement because of increased muscle tone^[60][61]
• Fatigue: The prevalence of fatigue in PD patients is 33 to 58 percent^[62][63][64] it’s mostly associated with depression and excessive day time somnolence but can occur as an isolate problem too.^[64][63][65]
• Olfactory dysfunction: Deficits in odor identification and discrimination are common in PD^[66] and can happen even before the motor symptoms of the disease.^[67][68]
• Pain: 46 percent of PD patients experience pain as a sense of lancinating, burning or tingling. The pain can be generalized or localized and can happen in different body areas like face, joints and genitals.^[69][70][71]

• Autonomic dysfunction: Autonomic dysfunction includes orthostatic hypotension, constipation, dysphagia, urinary and sexual problems.^[72][73] urinary symptoms is mostly cause by reduced bladder capacity due to detresor muscle contraction and manifest as frequency, urgency and urge incontinence.^[74][75] sexual dysfunction in men manifest with erection dysfunction and in women with vaginal tightness and lack of orgasm^[76][77]