Differentials
anemia
SIGNS / SYMPTOMS
History of menorrhagia, pallor on examination.
INVESTIGATIONS
CBC will show low hemoglobin and hematocrit.
supraventricular arrhythmias
SIGNS / SYMPTOMS
Examples include atrioventricular nodal reentrant tachycardia, atrial tachycardia, atrial flutter.
Symptoms may occur at rest or exertion, rather than by change in posture.
INVESTIGATIONS
Holter monitor will show ventricular rate >100 bpm with a narrow QRS complex (QRS width <120 ms) that is unrelated to posture.[46] However, more prolonged cardiac monitoring (4 weeks event monitor or loop recorder) is occasionally needed.
heart failure
SIGNS / SYMPTOMS
May have a history of dyspnea (and possibly orthopnea and paroxysmal nocturnal dyspnea).
Examination may show pitting edema of the lower extremities and distended jugular veins.
INVESTIGATIONS
Elevated B-type natriuretic peptide (BNP)/N-terminal pro-brain natriuretic peptide (NT-pro-BNP) levels.
Chest x-ray may show cardiomegaly, pulmonary edema, pleural effusion.
Echocardiogram will show depressed and dilated left and/or right ventricle with low ejection fraction if there is systolic heart failure, and normal left ventricular ejection fraction but left ventricular hypertrophy and abnormal diastolic filling patterns if there is diastolic heart failure.
hyperthyroidism
SIGNS / SYMPTOMS
Clinical features include weight loss, anxiety, insomnia, and amenorrhea.
INVESTIGATIONS
Low thyroid-stimulating hormone and elevated or normal free thyroxine and free triiodothyronine.
primary adrenal insufficiency (Addison disease)
SIGNS / SYMPTOMS
Clinical features include weight loss, myalgias, generalized weakness associated with mucocutaneous hyperpigmentation, and salt craving.
pheochromocytoma
SIGNS / SYMPTOMS
Clinical features include palpitations, sustained or paroxysmal hypertension (with associated hypertensive retinopathy if uncontrolled), diaphoresis, and pallor.
INVESTIGATIONS
Elevated urinary catecholamines, metanephrines, and normetanephrines.
Elevated serum free metanephrines and normetanephrines.
Plasma catecholamines may be elevated.
inappropriate sinus tachycardia
SIGNS / SYMPTOMS
On examination, there will be resting tachycardia with heart rate >100 bpm that is unrelated to change in posture.
INVESTIGATIONS
Holter monitor will show resting sinus tachycardia with heart rate >100 bpm for large periods of time that is unrelated to change in posture.
drugs
SIGNS / SYMPTOMS
Medications that may mimic POTS include stimulants (e.g., medications for attention deficit disorder), alpha-adrenergic blockers, high doses of beta-blockers (note that low doses of beta-blockers can be beneficial), calcium-channel blockers, serotonin-norepinephrine reuptake inhibitors, monoamine oxidase inhibitors, tricyclic antidepressants, and phenothiazines.[4]
Misuse of certain recreational drugs can also mimic or exacerbate POTS, which include cocaine and methamphetamines.[1][2][4]
INVESTIGATIONS
Clinical diagnosis.
anorexia nervosa
SIGNS / SYMPTOMS
Clinical features include low body mass index, fear of gaining weight, food restriction, disturbed body image, amenorrhea, suicidal ideation, binge eating and/or purging, bradycardia, hypothermia, hair loss, muscle wasting, and signs of cardiomyopathy. There may be comorbid psychiatric disorders, and the history may be denied by the patient.
INVESTIGATIONS
CBC may show anemia, mild leukopenia, or thrombocytopenia.
Basic metabolic panel may be deranged.
Serum glucose level may show hypoglycemia.
Serum creatinine level is generally low due to decreased muscle mass but may be elevated if renal failure is present.
Thyroid function tests may show low triiodothyronine, but thyroxine and thyroid-stimulating hormone are typically normal.
Liver function tests may be elevated.
anxiety disorder
SIGNS / SYMPTOMS
History of chronic, excessive anxiety and worry about a number of events or activities for at least 6 months, which causes distress and impairment.[50] In adults, at least three key symptoms out of a possible six are required to make a diagnosis (only one is required in children).[50]
INVESTIGATIONS
Clinical diagnosis.
pain
SIGNS / SYMPTOMS
History of pain. Associated symptoms may be present, depending on the location and cause of the pain, and whether this is acute or chronic.
INVESTIGATIONS
Clinical diagnosis.
infection
SIGNS / SYMPTOMS
Clinical features depend on the severity and source of the infection (e.g., purulent sputum and dyspnea with pneumonia, macular erythema with tenderness, warmth, and edema with cellulitis).
Suspect sepsis if there is acute deterioration in a patient in whom there is clinical evidence or strong suspicion of infection.[51] Take into account that people with sepsis may have nonspecific, nonlocalised presentations, such as feeling very unwell, and may not have a high temperature.[51]
INVESTIGATIONS
Other investigations, depending on the underlying cause, may show source of infection (e.g., new infiltrate on chest x-ray with pneumonia).
dehydration
SIGNS / SYMPTOMS
Clinical features include thirst, weak pulse, dry mucous membranes, and decreased skin turgor. Other features depend on the underlying cause (e.g., decreased oral intake, vomiting and diarrhea, profound sweating, diabetic ketoacidosis or hyperosmolar hyperglycemic state).
INVESTIGATIONS
Blood tests may show elevated BUN and creatinine.
ECG may show sinus tachycardia, or tachyarrhythmia.
Urinalysis may show high specific gravity.
severe deconditioning caused by prolonged bed rest
SIGNS / SYMPTOMS
History of prolonged bed rest.
INVESTIGATIONS
Clinical diagnosis.
mastocytosis
SIGNS / SYMPTOMS
Acquired solitary or widespread cutaneous eruption, lesion periodically urticates and blisters then returns to original form. Lesions are typically 5 mm to 15 mm papules, yellow-brown to yellow-red in color. There is typically edema, urtication, and vesicle and bullae formation, with urticaria surrounding an erythematous flare when rubbed (Darier sign).
INVESTIGATIONS
Skin scraping from base of bullae demonstrates mast cells (Giemsa or Wright stain).
systemic lupus erythematosus
SIGNS / SYMPTOMS
Malar (butterfly), photosensitive, or discoid rash can be present. Constitutional symptoms such as weight loss and fever are common. There may be prominent arthralgia and myalgia out of proportion to joint findings.
INVESTIGATIONS
Antinuclear antibodies will be positive.
Sjogren syndrome
SIGNS / SYMPTOMS
Dry eyes and dry mouth are common key features.
INVESTIGATIONS
Positive anti-60 kD (SS-A) Ro and anti-La (SS-B).
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