Huntington’s disease

Also called Huntington’s chorea, hereditary chorea, chronic progressive chorea, and adult chorea, Huntington’s disease is a hereditary disease in which degeneration in the cerebral cortex and basal ganglia causes chronic progressive chorea (involuntary and irregular movements) and cognitive deterioration, ending in dementia.

Huntington’s disease usually strikes people between ages 25 and 55 (the average age is 35); however, 2% of cases occur in children, and 5%, as late as age 60. Males and females are equally affected. Death usually results 10 to 15 years after onset from suicide, heart failure, or pneumonia.
Causes
Huntington’s disease is transmitted as an autosomal dominant trait, and either sex can transmit and inherit it. Each child of a parent with this disease has a 50% chance of inheriting it; the child who inherits it can pass it on to his own children.
Because of hereditary transmission, Huntington’s disease is prevalent in areas in which affected families have lived for several generations. Genetic testing is offered to those with a known family history of the disease.
Signs and symptoms
The onset of this disease is insidious. The patient eventually becomes totally dependent—emotionally and physically—through loss of musculoskeletal control.
Neurologic manifestations
Gradually, the patient develops progressively severe choreic movements. Such movements are rapid, usually violent, and purposeless. Initially, they’re unilateral and more prominent in the face and arms than in the legs, progressing from mild fidgeting to grimacing, tongue smacking, dysarthria (indistinct speech), athetoid movements (slow, twisting muscle contractions, especially of the hands) related to emotional state, and torticollis (neck muscle contractions).
Bradykinesia (slow movements) is commonly accompanied by rigidity. Muscle strength is generally maintained. The combination of chorea, bradykinesia, and normal muscle strength results in Continue reading “Huntington’s disease”

Introduction to Pituitary tumors

Pituitary tumorsConstituting 10% of intracranial neoplasms, pituitary tumors typically originate in the anterior pituitary (adenohypophysis). They occur in adults of both sexes, usually during the third and fourth decades of life. The three tissue types of pituitary tumors are chromophobe adenoma (90%), basophil adenoma, and eosinophil adenoma.
The prognosis is fair to good, depending on the extent to which the tumor spreads beyond the sella turcica.
Causes
Although the exact cause is unknown, a predisposition to pituitary tumors may be inherited through an autosomal dominant trait. Some are part of a hereditary disorder called multiple endocrine neoplasia 1. Pituitary tumors aren’t malignant in the strict sense; however, because their growth is invasive, they’re considered a neoplastic disease.
Chromophobe adenoma may be associated with the production of corticotropin, melanocyte-stimulating hormone, growth hormone, and prolactin; basophil adenoma, with evidence of excess corticotropin production and, consequently, with signs of Cushing’s syndrome; and eosinophil adenoma, with excessive growth hormone.
Signs and symptoms
As pituitary adenomas grow, they replace normal glandular tissue and enlarge the sella turcica, which houses the pituitary gland. The resulting pressure on adjacent intracranial structures produces typical clinical features.
Neurologic features
  • Frontal headache
  • Visual symptoms, beginning with blurring and progressing to field cuts (hemianopias) and then unilateral blindness
  • Cranial nerve involvement (III, IV, VI) from lateral extension of the tumor, resulting in strabismus; double vision, with compensating head tilting and dizziness; conjugate deviation of gaze; nystagmus; lid ptosis; and limited eye movements
  • Increased intracranial pressure (secondary hydrocephalus)
  • Personality changes or dementia, if the tumor breaks through to the frontal lobes
  • Seizures
  • Rhinorrhea, if the tumor erodes the base of the skull Continue reading “Introduction to Pituitary tumors”

Brief Summary of Peptic ulcers

Peptic ulcer is a disruption in the gastric or duodenal mucosa when normal defense mechanisms are overwhelmed or impaired by acid or pepsin. Ulcers are circumscribed lesions that extend through the muscularis mucosa. Ulcers are five times more common on the duodenum.
Causes
Researchers recognize three major causes of peptic ulcer disease: infection with Helicobacter pylori, use of nonsteroidal anti-inflammatory drugs (NSAIDs), and pathologic hypersecretory states such as Zollinger-Ellison syndrome.
H. pylori is the cause of the majority of duodenal and gastric ulcers. Following treatment with standard therapies, 70% to 85% of patients have a documented recurrence (by endoscopy) within 1 year.
Other causes include the use of certain drugs, such as salicylates and other NSAIDs, which encourage ulcer formation by inhibiting the secretion of prostaglandins (the substances that suppress ulceration). Certain illnesses— such as pancreatitis, hepatic disease, Crohn’s disease, Zollinger-Ellison syndrome, and preexisting gastritis — are also known causes. Additionally, having a type A personality increases autonomic nervous system effects on the gastric mucosa.
Predisposing factors
Ulcers are more common in smokers and those who regularly use NSAIDs. (Smoking increases the amount of hydrochloric acid in the stomach; nicotine reduces the bicarbonate content of pancreatic secretions and also decreases the degree of acid neutralization.) Diet and alcohol don’t appear to contribute to the development of peptic ulcer disease. It’s unclear whether emotional stress is a contributing factor.
Signs and symptoms
Symptoms vary with the type of ulcer.
Gastric ulcers
Gastric ulcers are usually signaled by pain that becomes more intense with eating. The pain is usually constant because the gastric mucosa is sensitive to acid secretion. Nausea or anorexia may occur.
Duodenal ulcers
Duodenal ulcers produce epigastric pain that’s gnawing, dull, aching, or “hunger-like.” The pain is Continue reading “Brief Summary of Peptic ulcers”

Severe combined immunodeficiency disease

Both cell-mediated (T-cell) and humoral (B-cell) immunity are deficient or absent in severe combined immunodeficiency disease (SCID). This results in susceptibility to infection from all classes of microorganisms during infancy.
At least three types of SCID exist: reticular dysgenesis, the most severe type, in which the hematopoietic stem cell fails to differentiate into lymphocytes and granulocytes; Swiss-type agammaglobulinemia, in which the hematopoietic stem cell fails to differentiate into lymphocytes alone; and enzyme deficiency, such as adenosine deaminase (ADA) deficiency, in which
the buildup of toxic products in the lymphoid tissue causes damage and subsequent dysfunction.
SCID affects more males than females; its estimated incidence is 1 in every 100,000 to 500,000 births. Most untreated patients die from infection within 1 year of birth.
Causes
SCID is usually transmitted as an autosomal recessive trait, although it may be X-linked. In most cases, the genetic defect seems associated with failure of the stem cell to differentiate into T and B lymphocytes.
Many molecular defects, such as mutation of the kinase ZAP-70, can cause SCID. X-linked SCID results from a mutation of a subunit of the interleukin-2 (IL-2), IL-4, and IL-7 receptors. Less commonly, it results from an enzyme deficiency.
Signs and symptoms
An extreme susceptibility to infection becomes obvious in the infant with SCID in the first months of life. The infant fails to thrive and develops chronic otitis, sepsis, watery diarrhea (associated with Salmonella or Escherichia coli), recurrent pulmonary infections (usually caused by Pseudomonas, cytomegalo-virus, or Pneumocystis carinii), persistent oral candidiasis (sometimes with esophageal erosions), and possibly fatal viral infections (such as chickenpox).
P. carinii pneumonia usually strikes a severely immunodeficient infant in the first 3 to 5 weeks of life. Onset is typically insidious, with gradually worsening cough, low-grade fever, tachypnea, and respiratory distress. A chest X-ray characteristically shows bilateral pulmonary infiltrates.
Diagnosis
Clinical indications point to the diagnosis. Most infants with SCID suffer recurrent overwhelming Continue reading “Severe combined immunodeficiency disease”

Introduction to Keratitis

Keratitis, also known as inflammation of the cornea, may be acute or chronic, superficial or deep. Superficial keratitis is fairly common and may develop at any age. The prognosis is good with treatment. Untreated, recurrent keratitis may lead to blindness.
Causes
Keratitis may result from exposure (as in Bell’s palsy where the eyelids don’t close), wearing contact lenses for prolonged periods (overnight), or corneal trauma. It may also result from infection by herpes simplex virus, type 1 (known as dendritic keratitis because of a characteristic branched lesion of the cornea resembling the veins of a leaf). Less commonly, it stems from bacterial or fungal infection; rarely, from congenital syphilis.
Signs and symptoms
Unilateral keratitis may produce pain, tearing, and photophobia. If the infection is in the center of the cornea, it may produce blurred vision. Left untreated, corneal opacities can occur. When keratitis results from exposure, it usually affects the lower portion of the cornea.
Diagnosis
A slit-lamp examination reveals the depth of the keratitis. If it’s due to herpes simplex virus, Continue reading “Introduction to Keratitis”

Abdominal Aneurysm

With abdominal aneurysm, an abnormal dilation in the arterial wall generally occurs in the aorta between the renal arteries and iliac branches. Such aneurysms are four times more common in men than in women and are most prevalent in whites ages 50 to 80. More than 50% of all people with untreated abdominal aneurysms die within 2 years of diagnosis, primarily from rupture of the aneurysm; more than 85%, within 5 years.
Causes
About 95% of abdominal aortic aneurysms result from arteriosclerosis; the rest, from cystic medial necrosis, trauma, syphilis, and other infections. These aneurysms develop slowly.
First, a focal weakness in the muscular layer of the aorta (tunica media), due to degenerative changes, allows the inner layer (tunica intima) and outer layer (tunica adventitia) to stretch outward. Blood pressure within the aorta progressively weakens the vessel walls and enlarges the aneurysm.
Signs and symptoms
Although abdominal aneurysms usually don’t produce symptoms, most are evident (unless the patient is obese) as a pulsating mass in the periumbilical area, accompanied by a systolic bruit over the aorta. Some tenderness may be present on deep palpation. A large aneurysm may produce symptoms that mimic renal calculi, lumbar disk disease, and duodenal compression. Abdominal aneurysms rarely cause diminished peripheral pulses or claudication unless embolization occurs.
Pain, rupture, and hemorrhage
Lumbar pain that radiates to the flank and groin from pressure on lumbar nerves may signify enlargement and imminent rupture. If the aneurysm ruptures into the peritoneal cavity, it causes severe, persistent abdominal and back pain, mimicking renal or ureteral colic. Continue reading “Abdominal Aneurysm”

Thyroid cancer

Thyroid cancerThyroid cancer occurs in all age groups, especially in persons who have had radiation treatment to the neck area. Papillary and follicular carcinomas are most common and are usually associated with prolonged survival.
Papillary carcinoma accounts for half of all thyroid cancers in adults; it’s most common in young adult females and metastasizes slowly. It’s the least virulent form of thyroid cancer. Follicular carcinoma is less common but more likely to recur and metastasize to the regional nodes and through blood vessels into the bones, liver, and lungs.
Medullary carcinoma originates in the parafollicular cells derived from the last branchial pouch and contains amyloid and calcium deposits. It can produce calcitonin, histaminase, corticotropin (producing Cushing’s syndrome), and prostaglandin E2 and F3 (producing diarrhea).
This rare form of thyroid cancer is familial, associated with pheochromocytoma, and completely curable when detected before it causes symptoms. Untreated, it progresses rapidly.
Seldom curable by resection, giant and spindle cell cancer (anaplastic tumor) resists radiation and metastasizes rapidly.
Causes
Predisposing factors include radiation exposure, prolonged thyrotropin stimulation (through radiation or heredity), familial predisposition, or chronic goiter.
Signs and symptoms
The primary signs of thyroid cancer are a painless nodule, a hard nodule in an enlarged thyroid gland, or palpable lymph nodes with thyroid enlargement. Eventually, the pressure of such a nodule or enlargement causes hoarseness, dysphagia, dyspnea, and pain on palpation.
If the tumor is large enough to destroy the gland, hypothyroidism follows, with its typical symptoms of low metabolism (mental apathy and sensitivity to cold). However, if the tumor stimulates excess thyroid hormone production, it induces symptoms of thyrotoxicosis (sensitivity to heat, restlessness, and hyperactivity).
Other clinical features include diarrhea, anorexia, irritability, vocal cord paralysis, and symptoms Continue reading “Thyroid cancer”

Introduction to Dermatophytosis

Also called tinea or ringworm, dermatophytosis is a disease that can affect the scalp (tinea capitis), body (tinea corporis), nails (tinea unguium), feet (tinea pedis), groin (tinea cruris), and bearded skin (tinea barbae).
Tinea infections are quite prevalent in the United States and are usually more common in males than in females. With effective treatment, the cure rate is very high, although about 20% of persons with infected feet or nails develop chronic conditions.
Causes
Tinea infections (except for tinea versicolor) result from dermatophytes (noncandidal fungi) of the genera Trichophyton, Microsporum, and Epidermophyton that involve the stratum corneum, nails or hair.
Transmission can occur directly (through contact with infected lesions) or indirectly (through contact with contaminated articles, such as shoes, towels, or shower stalls). Some cases come from animals or soil.
Signs and symptoms
Lesions vary in appearance and duration with the type of infection:
  • Tinea capitis, which mainly affects children, is characterized by round erythematous patches on the scalp, causing hair loss with scaling. In some children, a hypersensitivity reaction develops, leading to boggy, inflamed, commonly pus-filled lesions (kerions).
  • Tinea corporis produces flat lesions on the skin at any site except the scalp, bearded skin, groin, palms, or soles. These lesions may be dry and scaly or moist and crusty; as they enlarge, their centers heal, causing the classic ring-shaped appearance.
  • Tinea unguium (onychomycosis) infection typically starts at the tip of one or more toenails (fingernail infection is less common) and produces gradual thickening, discoloration, and crumbling of the nail, with accumulation of subungual debris. Eventually, the nail may be destroyed completely.
  • Tinea pedis causes scaling and blisters between the toes. Severe infection may result in inflammation, with severe itching and pain on walking. A dry, squamous inflammation may affect the entire sole.
  • Tinea cruris (jock itch) produces red, raised, sharply defined, itchy lesions in the groin that may extend to the buttocks, inner thighs, and the external genitalia. Warm weather and tight clothing encourage fungus growth. Continue reading “Introduction to Dermatophytosis”

Brief Summary of Anthrax

Anthrax is an acute bacterial infection that most commonly occurs in grazing animals, such as cattle, sheep, goats, and horses. It can also affect people who come in contact with contaminated animals or their hides, bones, fur, hair, or wool. It’s also used as an agent for bioterrorism and biological warfare.
Anthrax occurs worldwide but is most common in developing countries. In humans, anthrax occurs in three forms, depending on the mode of transmission: cutaneous, inhalational, and GI.

Causes
Anthrax is caused by the bacteria Bacillus anthracis, which exists in the soil as spores that can live for years. Transmission to humans usually occurs through exposure to or handling of infected animals or animal products. Anthrax spores can enter the body through abraded or broken skin (cutaneous anthrax), by inhalation (inhalational anthrax), or through ingestion of undercooked meat from an infected animal (GI anthrax). Anthrax isn’t known to spread from person-to-person.

Signs and symptoms
From the time of exposure, signs and symptoms of infection usually occur within 1 to 7 days but may take as long as 60 days to appear. The signs and symptoms of anthrax depend on the form acquired:

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Cutaneous anthrax: This is the most common form of anthrax. Skin infection may begin as a small, elevated, itchy lesion that resembles an insect bite, develops into a vesicle in 1 to 2 days, and finally becomes a small, painless ulcer with a necrotic (black) center. Enlarged lymph glands in the surrounding area are common. Without treatment, the mortality rate from cutaneous anthrax is 20%; the mortality rate is less than 1% with treatment.
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Inhalational anthrax: The patient may initially report flulike signs and symptoms, such as malaise, fever, headache, myalgia, and chills. Such milder signs and symptoms may progress to severe Continue reading “Brief Summary of Anthrax”

Guillain-Barré syndrome

guillain-barr-syndromeAlso known as infectious polyneuritis, Landry-Guillain-Barré syndrome, and acute idiopathic polyneuritis, Guillain-Barré syndrome is an acute, rapidly progressive, and potentially fatal form of polyneuritis that causes muscle weakness and mild distal sensory loss.
This syndrome can occur at any age but is most common between ages 30 and 50; it affects both sexes equally. Recovery is spontaneous and complete in about 95% of patients, although mild motor or reflex deficits in the feet and legs may persist. The prognosis is best when symptoms clear between 15 and 20 days after onset.
Causes
The precise cause of Guillain-Barré syndrome is unknown, but it may be a cell-mediated immune response with an attack on peripheral nerves in response to a virus. The major pathologic effect is segmental demyelination of the peripheral nerves.
Because this syndrome causes inflammation and degenerative changes in both the posterior (sensory) and the anterior (motor) nerve roots, signs of sensory and motor losses occur simultaneously.
Predisposing factors
About 50% of patients with Guillain-Barré syndrome have a recent history of minor febrile illness, usually an upper respiratory tract infection or, less commonly, gastroenteritis. When infection precedes the onset of Guillain-Barré syndrome, signs of infection subside before neurologic features appear.
Other possible precipitating factors include surgery, rabies or swine influenza vaccination, viral illness, Hodgkin’s or some other malignant disease, and systemic lupus erythematosus.
Signs and symptoms
Muscle weakness, the major neurologic sign, usually appears in the legs first (ascending type) and then extends to the arms and facial nerves within 24 to 72 hours. Sometimes, muscle weakness develops in the arms first (descending type) or in the arms and legs simultaneously. In milder forms of the disease, muscle weakness may affect only the cranial nerves or may not occur.
Paresthesia, another common neurologic sign, sometimes precedes muscle weakness but vanishes quickly. Some patients with the disorder never develop this symptom.
Other clinical features include facial diplegia (possibly with ophthalmoplegia [ocular paralysis]), dysphagia or dysarthria and, less commonly, weakness of the muscles supplied by cranial nerve XI (spinal accessory nerve).
Muscle weakness develops so quickly that muscle atrophy doesn’t occur, but hypotonia and areflexia do. Stiffness and pain in the form of a severe “charley horse” occur in many cases.
Three-phase course
The clinical course of Guillain-Barré syndrome is divided into three phases: