The Great Imitator (also the Great Masquerader) is a phrase used for medical conditions that feature nonspecific symptoms and may be confused with a number of other diseases. [1] The term connotes especially difficult differential diagnosis (DDx), especial potential for misdiagnosis, and the protean nature of some diseases. Most great imitators are systemic in nature or have systemic sequelae, and an aspect of nonspecific symptoms is logically almost always involved. In some cases, an assumption that a particular sign or symptom, or a particular pattern of several thereof, is pathognomonic turns out to be false, as the reality is that it is only nearly so.
As recently as the 1950s, syphilis was widely considered by physicians to be "the great imitator", and in the next few decades after that, several other candidates, mainly tuberculosis [2] but occasionally others, [3] were asserted as being "the second great imitator". But because differential diagnosis is inherently subject to occasional difficulty and to false positives and false negatives, the idea that there are only one or two great imitators was more melodrama than objective description. In recent decades, more than a dozen diseases have been recognized in the medical literature as worthy of being considered great imitators, on the common theme of recurring misdiagnoses/missed diagnoses and protean manifestations. Nonetheless, not every DDx caveat (not every mimic) meets the threshold, because it is inherent to DDx generally that there are thousands of caveats (thousands of instances of the theme, "be careful to rule out X before diagnosing Y"); for example, ectopic pregnancy and ovarian neoplasia can mimic each other, as can myocardial infarction and panic attack, but they are not established as great imitators per se (rather, merely DDx considerations). The list of great imitators here relies on references in the medical literature applying that label, or on other references documenting a condition's especially recurrent and poignant reputation for misdiagnoses.
Conditions or diseases sometimes referred to with this nickname thus include the following:
Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, a round red face due to facial plethora, a fat lump between the shoulders, weak muscles, weak bones, acne, and fragile skin that heals poorly. Women may have more hair and irregular menstruation. Occasionally there may be changes in mood, headaches, and a chronic feeling of tiredness.
Hirsutism is excessive body hair on parts of the body where hair is normally absent or minimal. The word is from early 17th century: from Latin hirsutus meaning "hairy". It usually refers to a male pattern of hair growth in a female that may be a sign of a more serious medical condition, especially if it develops well after puberty. Cultural stigma against hirsutism can cause much psychological distress and social difficulty. Discrimination based on facial hirsutism often leads to the avoidance of social situations and to symptoms of anxiety and depression.
Pheochromocytoma is a rare tumor of the adrenal medulla composed of chromaffin cells, also known as pheochromocytes. When a tumor composed of the same cells as a pheochromocytoma develops outside the adrenal gland, it is referred to as a paraganglioma. These neuroendocrine tumors typically release massive amounts of catecholamines which result in the most common symptoms, including hypertension, tachycardia, and sweating. Rarely, some tumors may secrete little to no catecholamines, making diagnosis difficult. While tumors of the head and neck are parasympathetic, their sympathetic counterparts are predominantly located in the abdomen and pelvis, particularly concentrated at the organ of Zuckerkandl.
Lichen planus (LP) is a chronic inflammatory and autoimmune disease that affects the skin, nails, hair, and mucous membranes. It is not an actual lichen, but is named for its appearance. It is characterized by polygonal, flat-topped, violaceous papules and plaques with overlying, reticulated, fine white scale, commonly affecting dorsal hands, flexural wrists and forearms, trunk, anterior lower legs and oral mucosa. The hue may be gray-brown in people with darker skin. Although there is a broad clinical range of LP manifestations, the skin and oral cavity remain as the major sites of involvement. The cause is unknown, but it is thought to be the result of an autoimmune process with an unknown initial trigger. There is no cure, but many different medications and procedures have been used in efforts to control the symptoms.
Pituitary adenomas are tumors that occur in the pituitary gland. Most pituitary tumors are benign, approximately 35% are invasive and just 0.1% to 0.2% are carcinomas. Pituitary adenomas represent from 10% to 25% of all intracranial neoplasms and the estimated prevalence rate in the general population is approximately 17%.
A seborrheic keratosis is a non-cancerous (benign) skin tumour that originates from cells, namely keratinocytes, in the outer layer of the skin called the epidermis. Like liver spots, seborrheic keratoses are seen more often as people age.
Hyperandrogenism is a medical condition characterized by high levels of androgens. It is more common in women than men. Symptoms of hyperandrogenism may include acne, seborrhea, hair loss on the scalp, increased body or facial hair, and infrequent or absent menstruation. Complications may include high blood cholesterol and diabetes. It occurs in approximately 5% of women of reproductive age.
Mycosis fungoides, also known as Alibert-Bazin syndrome or granuloma fungoides, is the most common form of cutaneous T-cell lymphoma. It generally affects the skin, but may progress internally over time. Symptoms include rash, tumors, skin lesions, and itchy skin.
Pruritic urticarial papules and plaques of pregnancy (PUPPP), known in United Kingdom as polymorphic eruption of pregnancy (PEP), is a chronic hives-like rash that strikes some women during pregnancy. Some skin changes are known to occur in people who are pregnant while other skin conditions, or dermatoses, that people have prior to getting pregnant will become altered or symptoms will increase. Pruritic urticarial papules and plaques of pregnancy (PUPPP) is one of many skin conditions that is specific to pregnancy and occurs in about 1 in every 160 (0.625%) of pregnancies.
Psychodermatology is the treatment of skin disorders using psychological and psychiatric techniques by addressing the interaction between mind and skin. Though historically there has not been strong scientific support for its practice, there is increasing evidence that behavioral treatments may be effective in the management of chronic skin disorders.
A paraneoplastic syndrome is a syndrome that is the consequence of a tumor in the body. It is specifically due to the production of chemical signaling molecules by tumor cells or by an immune response against the tumor. Unlike a mass effect, it is not due to the local presence of cancer cells.
Angiofibroma (AGF) is a descriptive term for a wide range of benign skin or mucous membrane lesions in which individuals have:
Parathyroid carcinoma is a rare cancer resulting in parathyroid adenoma to carcinoma progression. It forms in tissues of one or more of the parathyroid glands.
Neonatal acne, also known as acne neonatorum, is an acneiform eruption that occurs in newborns or infants within the first 4-6 weeks of life, and presents with open and closed comedones on the cheeks, chin and forehead.
Genital leiomyomas are leiomyomas that originate in the dartos muscles, or smooth muscles, of the genitalia, areola, and nipple. They are a subtype of cutaneous leiomyomas that affect smooth muscle found in the scrotum, labia, or nipple. They are benign tumors, but may cause pain and discomfort to patients. Genital leiomyoma can be symptomatic or asymptomatic and is dependent on the type of leiomyoma. In most cases, pain in the affected area or region is most common. For vaginal leiomyoma, vaginal bleeding and pain may occur. Uterine leiomyoma may exhibit pain in the area as well as painful bowel movement and/or sexual intercourse. Nipple pain, enlargement, and tenderness can be a symptom of nipple-areolar leiomyomas. Genital leiomyomas can be caused by multiple factors, one can be genetic mutations that affect hormones such as estrogen and progesterone. Moreover, risk factors to the development of genital leiomyomas include age, race, and gender. Ultrasound and imaging procedures are used to diagnose genital leiomyomas, while surgically removing the tumor is the most common treatment of these diseases. Case studies for nipple areolar, scrotal, and uterine leiomyoma were used, since there were not enough secondary resources to provide more evidence.
Acral persistent papular mucinosis (APPM) is a rare form of lichen myxedematosus. It is characterized by small papules on the backs of the hands, wrists, and extensor aspects of the distal forearms, with no further clinical or laboratory indications. Lesions tend to persist and may grow in number gradually. Because there are no symptoms, treatment is rarely required.
Koenen's tumor (KT), also commonly termed periungual angiofibroma, is a subtype of the angiofibromas. Angiofibromas are benign papule, nodule, and/or tumor lesions that are separated into various subtypes based primarily on the characteristic locations of their lesions. KTs are angiofibromas that develop in and under the toenails and/or fingernails. KTs were once considered as the same as another subtype of the angiofibromas viz., acral angiofibromas. While the literature may still sometimes regard KTs as acral angiofibromas, acral angiofibromas are characteristically located in areas close to but not in the toenails and fingernails as well as in the soles of the feet and palms of the hands. KTs are here regarded as distinct from acral angiofibromas.
Boston exanthem disease is a cutaneous condition that first occurred as an epidemic in Boston in 1951. It is caused by echovirus 16. The disease tends to afflict children more often than adults, although some adults can become infected, and the symptoms have never been fatal. It shows some clinical similarity to Rubella and Human herpesvirus 6
Depression, one of the most commonly diagnosed psychiatric disorders, is being diagnosed in increasing numbers in various segments of the population worldwide. Depression in the United States alone affects 17.6 million Americans each year or 1 in 6 people. Depressed patients are at increased risk of type 2 diabetes, cardiovascular disease and suicide. Within the next twenty years depression is expected to become the second leading cause of disability worldwide and the leading cause in high-income nations, including the United States. In approximately 75% of suicides, the individuals had seen a physician within the prior year before their death, 45–66% within the prior month. About a third of those who died by suicide had contact with mental health services in the prior year, a fifth within the preceding month.
A pancreatic tumor is an abnormal growth in the pancreas. In adults, almost 90% are pancreatic cancer and a few are benign. Pancreatic tumors are rare in children.
Oral cancer has been called the great imitator, for it can appear as many different oral conditions.
Because of its protean and often nonspecific clinical manifestation, RCC is sometimes referred to as the 'great imitator' by clinicians.
Substance abuse has been called the "great imitator" of our time for good reason.
Often called "the great imitator," gout may masquerade as septic arthritis, RA, or neoplasm, and the diagnosis is often delayed by weeks or months.
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: CS1 maint: postscript (link)Scabies is called the great imitator because patients can present with a variety of lesions.