NEET MDS Lessons
General Pathology
Systemic Candidiasis (Candidosis; Moniliasis)
Invasive infections caused by Candida sp, most often C. albicans, manifested by fungemia, endocarditis, meningitis, and/or focal lesions in liver, spleen, kidneys, bone, skin, and subcutaneous or other tissues.
Infections due to Candida sp account for about 80% of all major systemic fungal infections.
Symptoms and Signs
Esophagitis is most often manifested by dysphagia. Symptoms of respiratory tract infections are nonspecific, such as cough. Vaginal infections cause itching, burning, and discharge. Candidemia usually causes fever, but other symptoms are typically nonspecific. Sometimes, a syndrome develops resembling bacterial sepsis, with a fulminating course that may include shock, oliguria, renal shutdown, and disseminated intravascular coagulation.
Hematogenous endophthalmitis starts as white retinal plaques that can cause blindness as destructive inflammation progresses, extending to opacify the vitreous and causing potentially irreversible scarring. Most often, there are no symptoms in early stages of Candida endophthalmitis. If treatment is not begun before symptoms appear, significant or even total loss of vision is likely to occur in the affected eye. In neutropenic patients, eye involvement is more often manifested by retinal hemorrhages; papulonodular, erythematous, and vasculitic skin lesions may also develop.
Cryptococcosis
An infection acquired by inhalation of soil contaminated with the encapsulated yeast Cryptococcus neoformans, which may cause a self-limited pulmonary infection or disseminate, especially to the meninges, but sometimes to the skin, bones, viscera, or other sites.
Cryptococcosis is a defining opportunistic infection for AIDS, although patients with Hodgkin's or other lymphomas or sarcoidosis or those receiving long-term corticosteroid therapy are also at increased risk.
AIDS-associated cryptococcal infection may present with severe, progressive pneumonia with acute dyspnea and an x-ray pattern suggestive of Pneumocystis infection.
Primary lesions in the lungs are usually asymptomatic and self-limited
Pneumonia usually causes cough and other nonspecific respiratory symptoms. Rarely, pyelonephritis occurs with renal papillary necrosis development.
Most symptoms of cryptococcal meningitis are attributable to brain swelling and are usually nonspecific, including headache, blurred vision, confusion, depression, agitation, or other behavioral changes. Except for ocular or facial palsies, focal signs are rare until relatively late in the course of infections. Blindness may develop due to brain swelling or direct involvement of the optic tracts. Fever is usually low-grade and frequently absent.
Osteopetrosis (Albers-Schönberg disease or marble bone disease)
is a group of rare genetic disorders characterized by reduced osteoclast-mediated bone resorption and therefore defective bone remodelling. The bones are solid and heavy with no medullary canal, long ends are bulbous, small neural foramina compress nerves. The affected bone is grossly dense but fractures occur readily like a piece of chalk.
Patients frequently have cranial nerve compressions by the surrouding bone, and recurrent infections. The latter is attributable to diminished hematopoiesis resulting from reduced marrow space with impressive hepatosplenomegaly due to extramedullary hematopoiesis
a. Caused by abnormal osteoclasts. This results in defective bone remodeling (i.e., abnormally low bone resorption) and increased bone density, which may invade into bone marrow space.
b. Causes severe defects in infants, including:
(1) Anemia and infections—caused by decreased bone marrow.
(2) Blindness, deafness, paralysis of facial muscles—caused by the narrowing of cranial nerve foramina.
(3) Is life-threatening.
(4) Oral findings include delayed eruption of teeth.
c. Disease is less severe in adults
Blastomycosis (North American Blastomycosis; Gilchrist's Disease)
A disease caused by inhalation of mold conidia (spores) of Blastomyces dermatitidis, which convert to yeasts and invade the lungs, occasionally spreading hematogenously to the skin or focal sites in other tissues.
Pulmonary blastomycosis tends to occur as individual cases of progressive infection
Symptoms are nonspecific and may include a productive or dry hacking cough, chest pain, dyspnea, fever, chills, and drenching sweats. Pleural effusion occurs occasionally. Some patients have rapidly progressive infections, and adult respiratory distress syndrome may develop.
Coccidioidomycosis (Valley Fever; San Joaquin Fever)
A disease caused by the fungus Coccidioides immitis, usually occurring in a primary form as an acute benign asymptomatic or self-limited respiratory infection, occasionally disseminating to cause focal lesions in skin, subcutaneous tissues, lymph nodes, bones, liver, kidneys, meninges, brain, or other tissues.
Primary coccidioidomycosis is usually asymptomatic, but nonspecific respiratory symptoms resembling influenza or acute bronchitis sometimes occur or, less often, acute pneumonia or pleural effusion. Symptoms, in decreasing order of frequency, include fever, cough, chest pain, chills, sputum production, sore throat, and hemoptysis.
Progressive disseminated coccidioidomycosis may develop a few weeks, months, or occasionally years after primary infections,, is more common in men than women and is more likely to occur in association with HIV infection, immunosuppressive therapy
Symptoms often are nonspecific, including low-grade fever, anorexia, weight loss, and weakness. Extensive pulmonary involvement may cause progressive cyanosis, dyspnea, and discharge of mucopurulent or bloody sputum. Extrapulmonary lesions are usually focal, involving one or more tissue sites in bones, joints, skin, subcutaneous tissues, viscera, brain, or meninges. Draining sinus tracts sometimes connect deeper lesions to the skin. Localized extrapulmonary lesions often become chronic and recur frequently, sometimes long after completion of seemingly successful antifungal therapy.