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The main intracellular cation is Potassium, which plays a crucial role in maintaining the cell's resting membrane potential and proper cellular function. Its concentration is significantly higher inside cells compared to outside, essential for nerve impulse transmission, muscle contraction, and heart rhythm regulation. In surgical and critical care settings, monitoring potassium levels is vital since imbalances can lead to life-threatening arrhythmias or muscle weakness. Sodium, by contrast, predominates extracellularly. Maintaining proper intracellular potassium levels is crucial for cellular homeostasis and patient stability during perioperative management.

Reference: Guyton and Hall Textbook of Medical Physiology, Guyton AC, Hall JE, 14th Edition.
An effective preventive measure for pinworm infection is hand hygiene because pinworm eggs are typically transmitted via the fecal-oral route. After scratching the perianal area, eggs can contaminate the fingers and subsequently be ingested or spread to surfaces, increasing the risk of reinfection and transmission to others. Frequent handwashing with soap and water interrupts this cycle by removing eggs from the hands before they can be ingested. This simple practice is the cornerstone of controlling pinworm infections, especially in children. Other measures are supportive but do not directly prevent transmission like hand hygiene does.

Reference: Mims’ Medical Microbiology, Richard Goering, 6th Edition.
Toxicity of Vitamin D leads to hypercalcemia because it increases the intestinal absorption of calcium and promotes bone resorption. Excessive Vitamin D raises serum calcium levels, causing symptoms like nausea, vomiting, polyuria, and nephrocalcinosis. This hypercalcemic effect is unique to Vitamin D toxicity, distinguishing it from other vitamins. Management focuses on stopping Vitamin D intake and addressing hypercalcemia.

Reference: Harrison’s Principles of Internal Medicine, J. Larry Jameson et al., 20th Edition.
Kernicterus is a serious neurological complication that occurs when unconjugated bilirubin crosses the immature blood-brain barrier in neonates. This leads to bilirubin-induced brain toxicity, primarily affecting the basal ganglia and brainstem nuclei. If untreated, severe jaundice can cause irreversible damage, resulting in movement disorders, hearing loss, and cognitive impairment. Early recognition and treatment of hyperbilirubinemia are essential to prevent this condition. Hence, kernicterus is the most critical complication of untreated neonatal jaundice.

Reference: Nelson Textbook of Pediatrics, Robert M. Kliegman et al., 21st Edition.
The fever pattern in brucellosis is typically relapsing because the infection causes intermittent bacteraemia as Brucella organisms multiply intracellularly and then are released periodically into the bloodstream. This leads to recurring febrile episodes separated by afebrile intervals. Unlike continuous or remittent fevers, the relapsing nature is a hallmark feature that helps differentiate brucellosis from other febrile illnesses. Recognizing this pattern is key to clinical diagnosis and management.

Reference: Harrison's Principles of Internal Medicine, Jameson et al., 20th Edition.
Untreated cholera causes profuse, watery diarrhea leading to rapid loss of fluids and electrolytes. This significant fluid loss results in severe dehydration, which reduces circulating blood volume causing hypovolemic shock. If not promptly managed with rehydration, this shock can progress to multi-organ failure and death. The primary life-threatening complication is therefore dehydration shock, making timely fluid replacement crucial. Other complications like renal failure or cardiac arrest may occur secondary to severe shock but are not the initial major issue.

Reference: Harrison's Principles of Internal Medicine, J. Larry Jameson, 20th Edition.
The skin biopsy is the most useful test for diagnosing leprosy as it allows direct visualization of the Mycobacterium leprae bacteria within nerve and skin tissue. Histopathological examination reveals specific features such as granulomas and acid-fast bacilli, confirming the diagnosis. This test also helps classify the disease type (tuberculoid or lepromatous), guiding appropriate treatment. Other tests like blood culture or imaging do not detect the organism reliably. Thus, a skin biopsy provides definitive evidence of leprosy infection.

Reference: Harrison's Principles of Internal Medicine, J. Larry Jameson et al., 20th Edition.
Unprotected sex is a major risk factor for HIV infection because it allows the direct exchange of bodily fluids such as semen, vaginal secretions, and blood, which can contain the HIV virus. Without the barrier protection of condoms, HIV can easily enter the body through mucous membranes or small tears in the genital area. This mode of transmission is responsible for the majority of new HIV infections worldwide. Preventive measures, such as consistent condom use, significantly reduce the risk of HIV transmission by blocking the virus from reaching susceptible cells.

Reference: Harrison’s Principles of Internal Medicine, Jameson et al., 20th Edition.
Hemoptysis, or coughing up blood, is a common and significant symptom of pulmonary tuberculosis (TB). It occurs due to the destruction of lung tissue and erosion of blood vessels by the Mycobacterium tuberculosis infection. This leads to cavitary lesions that predispose the patient to bleeding. Hemoptysis reflects active pulmonary involvement and is a critical clinical sign for TB diagnosis and monitoring. Unlike jaundice, polyuria, or bradycardia, which are not linked to pulmonary pathology, hemoptysis directly indicates respiratory tract damage in TB.

Reference: Harrison's Principles of Internal Medicine, J. Larry Jameson, 20th Edition.

ফ্রিতে ২ লাখ প্রশ্নের টপিক, সাব-টপিক ভিত্তিক ও ১০০০+ জব শুলুশন্স বিস্তারিতে ব্যাখ্যাসহ পড়তে ও আপনার পড়ার ট্র্যাকিং রাখতে সাইটে লগইন করুন।

লগইন করুন
The PCR of saliva is the preferred diagnostic test for confirming rabies in humans because it directly detects the presence of rabies viral RNA in body fluids during the early symptomatic phase. Serum antibody tests are not reliable in the acute phase as antibodies may take time to develop, and CSF analysis is nonspecific. PCR offers high sensitivity and specificity, enabling timely and accurate diagnosis essential for patient management and public health interventions. Urine culture is irrelevant for rabies diagnosis since rabies virus is not excreted in urine.

Reference: Harrison's Principles of Internal Medicine, Kasper et al., 20th Edition.
Plasmodium falciparum is most commonly associated with severe malaria because it infects red blood cells of all ages, leading to higher levels of parasitemia. This results in the sequestration of infected erythrocytes in small blood vessels, causing microvascular obstruction, tissue hypoxia, and organ dysfunction. P. falciparum’s ability to cause cerebral malaria, severe anemia, and multi-organ failure distinguishes it from other species. These factors contribute to its higher mortality and severity compared to P. vivax, P. malariae, and P. ovale.

Reference: Harrison's Principles of Internal Medicine, Kasper et al., 20th Edition.
Malnourished individuals have a weakened immune system, which impairs their ability to control Leishmania donovani infection, the causative agent of kala-azar (visceral leishmaniasis). This immunosuppressed state increases susceptibility to the parasite and progression to disease. Malnutrition particularly affects cell-mediated immunity, critical for controlling intracellular pathogens like Leishmania. Therefore, malnutrition is a major risk factor for the development and severity of kala-azar.

Reference: Harrison's Principles of Internal Medicine, Kasper et al., 20th Edition.
Amoebiasis primarily affects the colon because the causative organism, *Entamoeba histolytica*, invades the colonic mucosa after ingestion of contaminated food or water. This leads to ulceration and inflammation of the colonic lining, causing symptoms such as bloody diarrhea and abdominal pain. Although the liver can be secondarily involved via hematogenous spread (amebic liver abscess), the initial and primary site of infection is the colon. Effective treatment targets this region to prevent complications.

Reference: Harrison's Principles of Internal Medicine, Jameson et al., 20th Edition.
Blood culture is considered the gold standard and confirmatory test for diagnosing Salmonella typhi infection because it directly detects the presence of the bacteria in the bloodstream during the early phase of illness. It has higher specificity and allows for antibiotic sensitivity testing, which guides appropriate treatment. Other tests like the Widal test are less specific and may produce false positives due to previous vaccination or exposure. Urine culture and stool microscopy are less reliable in the acute phase and serve more as adjuncts in the later stages or carriers.

Reference: Harrison's Principles of Internal Medicine, J. Larry Jameson, 20th Edition.
Severe bleeding is a critical marker of severe dengue infection because it signifies the progression to dengue hemorrhagic fever or dengue shock syndrome, both of which can be life-threatening. This complication results from increased vascular permeability, thrombocytopenia, and coagulopathy, leading to hemorrhagic manifestations. Unlike mild rash, low-grade fever, or headache, which are common and non-specific symptoms, severe bleeding indicates a breakdown in hemostatic mechanisms and requires urgent medical intervention to prevent mortality. Prompt recognition of bleeding is essential to manage fluid resuscitation and support care.

Reference: Harrison’s Principles of Internal Medicine, Kasper et al., 20th Edition.
Antibiotic stewardship is essential in clinical practice because it reduces inappropriate use of antibiotics, which helps prevent the development of antibiotic resistance. By ensuring antibiotics are used only when necessary and with the correct choice, dose, and duration, stewardship programs improve patient outcomes and limit the spread of resistant organisms. This approach also preserves the effectiveness of existing antibiotics for future patients. Therefore, the primary goal of antibiotic stewardship is to promote responsible antibiotic use, not to increase costs or limit availability.

Reference: Principles and Practice of Infectious Diseases, Mandell, Douglas, and Bennett, 9th Edition.
Specimens should be collected before starting antibiotics to ensure accurate identification of the causative microorganism. Antibiotics administered prior to specimen collection can reduce the bacterial load, leading to false-negative cultures or altered microbial flora. This compromise in diagnostic accuracy may result in inappropriate treatment. Collecting specimens prior to antibiotic therapy allows for the isolation and sensitivity testing of pathogens, guiding targeted antimicrobial therapy and improving patient outcomes.

Reference: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Mandell et al., 9th Edition.
- Insulin is the principal hormone responsible for lowering blood glucose levels by promoting cellular uptake of glucose, particularly into muscle and adipose tissue, and by stimulating glycogenesis in the liver.
- It also inhibits hepatic gluconeogenesis and glycogenolysis, reducing endogenous glucose production.
- Unlike glucagon, cortisol, and growth hormone, which raise blood glucose, insulin directly facilitates glucose utilization and storage, thereby maintaining normal glycaemia.
- Its deficiency or resistance leads to hyperglycaemia, highlighting its critical role in glucose homeostasis.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: The Endocrine System, Page 340.
- The most frequent underlying cause of iron deficiency anemia in adults is chronic blood loss, commonly from the gastrointestinal tract.
- This continuous loss depletes iron stores over time, leading to anemia.
- In adults, dietary iron deficiency is less common due to generally adequate intake, while malabsorption and increased requirements (e.g., pregnancy) are less frequent causes.
- Identifying and treating the source of blood loss is essential for management.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Disorders of Iron Metabolism and Anemia, Page 591.

ফ্রিতে ২ লাখ প্রশ্নের টপিক, সাব-টপিক ভিত্তিক ও ১০০০+ জব শুলুশন্স বিস্তারিতে ব্যাখ্যাসহ পড়তে ও আপনার পড়ার ট্র্যাকিং রাখতে সাইটে লগইন করুন।

লগইন করুন
- The specific antidote for acute paracetamol toxicity is N-acetylcysteine, which acts by replenishing hepatic glutathione stores.
- This allows detoxification of the toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI), preventing hepatic cellular injury and fulminant liver failure.
- Early administration (preferably within 8–10 hours) significantly reduces morbidity and mortality.
- Methionine is an alternative but less commonly used. Atropine and flumazenil have no role in paracetamol poisoning management.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Disorders of Liver Function, Page 684.
- Genital herpes is caused by the herpes simplex virus (HSV), a viral pathogen characterized by painful genital ulcers and recurrent episodes due to latency in sensory ganglia.
- In contrast, Chlamydia trachomatis, Treponema pallidum (syphilis), and Neisseria gonorrhoeae are bacterial pathogens responsible for their respective infections.
- Recognition of genital herpes as a viral STI is critical for understanding its clinical course, transmission dynamics, and the approach to antiviral therapy.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Sexually Transmitted Infections, Page 1145.
- The presentation of a young boy with recurrent respiratory infections, eczema, and petechiae along with thrombocytopenia and an immunoglobulin pattern of decreased IgM and increased IgA and IgE is characteristic of Wiskott-Aldrich syndrome.
- This X-linked immunodeficiency results from defects in the WAS gene, leading to abnormal platelet formation (causing thrombocytopenia with small platelets) and impaired T-cell function causing susceptibility to infections.
- The altered immunoglobulin profile with low IgM and elevated IgA and IgE further supports this diagnosis.
- The triad of eczema, thrombocytopenia, and recurrent infections is pathognomonic of this syndrome.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Immunodeficiency, Page 506.
- Hashimoto's thyroiditis is a common autoimmune thyroid disorder characterized by the presence of anti-thyroid peroxidase (anti-TPO) antibodies and lymphocytic infiltration of the thyroid gland, leading to gradual thyroid failure and hypothyroidism.
- It is the most frequent cause of chronic autoimmune thyroiditis and presents with a painless, diffusely enlarged thyroid.
- Unlike De Quervain and subacute granulomatous thyroiditis, which are typically post-viral and self-limiting, Hashimoto’s is a chronic condition marked by autoimmune destruction of thyroid tissue.
- Riedel thyroiditis involves fibrous replacement and is rare, not autoimmune-mediated.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Disorders of the Thyroid Gland, Page 759.
- The patient’s presentation of confusion, high fever, dilated pupils, hyperreflexia, inducible clonus, and labile blood pressure after taking fluoxetine (a selective serotonin reuptake inhibitor) and sumatriptan (a serotonergic agent) is characteristic of serotonin syndrome.
- This syndrome results from excess serotonergic activity in the central nervous system.
- Key clinical features include neuromuscular hyperactivity (clonus, hyperreflexia), autonomic instability (labile BP, hyperthermia), and altered mental status.
- The rapid onset and combination of serotonergic drugs support this diagnosis, distinguishing it from neuroleptic malignant syndrome and other hyperthermic states.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Disorders of the Nervous System, Page 364.
- The first-line treatment for a patient with unstable ventricular tachycardia is synchronous cardioversion, because it delivers a timed electrical shock synchronized to the QRS complex, restoring normal rhythm without precipitating ventricular fibrillation.
- Unstable VT, characterized by hemodynamic compromise (e.g., hypotension, chest pain, altered consciousness), requires immediate rhythm control.
- Intravenous antiarrhythmics like amiodarone are used once the patient is stabilized or if VT is stable.
- Unsynchronized defibrillation is reserved for pulseless VT or ventricular fibrillation.
- Vagal maneuvers have no role in ventricular arrhythmias.
- Prompt cardioversion prevents clinical deterioration and sudden cardiac death.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Cardiac Arrhythmias, Page 600.
- Positive anti-mitochondrial antibodies (AMA) are the hallmark serological finding in primary biliary cholangitis (PBC), present in over 90% of cases and providing a highly specific diagnostic marker.
- AMA targets components of the mitochondrial inner membrane, reflecting autoimmune destruction of small intrahepatic bile ducts.
- While elevated alkaline phosphatase indicates cholestasis and anti-nuclear antibodies (ANA) can be seen, these are less specific.
- Liver biopsy can support diagnosis but is not definitive without AMA positivity.

Thus, AMA serology offers the most specific confirmation of PBC among available tests.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Diseases of the Liver and Biliary System, Page 684.
- Lipase is the most specific serum enzyme for diagnosing acute pancreatitis because it is produced primarily by the pancreas and remains elevated longer than amylase, allowing for a wider diagnostic window.
- Unlike amylase, lipase levels are less influenced by non-pancreatic conditions such as salivary gland disorders or intestinal diseases.
- Elevated serum lipase reflects pancreatic injury with higher sensitivity and specificity, making it the preferred biochemical marker in clinical practice.
- This specificity aids in distinguishing pancreatitis from other abdominal pathologies presenting with similar symptoms.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Disorders of the pancreas, Page 843.
- The presentation of bilateral hilar lymphadenopathy combined with non-caseating granulomas on transbronchial lung biopsy is characteristic of sarcoidosis.
- This systemic granulomatous disease commonly affects young adults, causing progressive dyspnea and dry cough.
- Unlike tuberculosis, sarcoidosis granulomas are non-caseating, and the absence of necrosis helps distinguish it from infectious causes.
- Hypersensitivity pneumonitis and Wegener’s granulomatosis have differing clinical and histological features, such as more prominent interstitial infiltration and necrotizing granulomas, respectively.
- Hence, the clinical and pathological findings strongly support the diagnosis of sarcoidosis.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Disorders of the respiratory system, Page 727.
- Streptococcus pneumoniae is the leading cause of community-acquired pneumonia in adults due to its high prevalence in the upper respiratory tract and ability to evade host defenses.
- It typically presents with sudden onset of fever, productive cough with purulent sputum, and chest pain.
- The organism’s polysaccharide capsule is a key virulence factor that enables it to resist phagocytosis and establish infection.
- Pneumococcal pneumonia is associated with lobar consolidation visible on chest X-ray, distinguishing it clinically and radiologically from atypical pneumonias.
- Effective treatment relies on antibiotics targeting this bacterium, emphasizing its importance as the primary causative agent in adult community-acquired pneumonia.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Lower Respiratory Tract Infections, Page 697.

ফ্রিতে ২ লাখ প্রশ্নের টপিক, সাব-টপিক ভিত্তিক ও ১০০০+ জব শুলুশন্স বিস্তারিতে ব্যাখ্যাসহ পড়তে ও আপনার পড়ার ট্র্যাকিং রাখতে সাইটে লগইন করুন।

লগইন করুন
- In iron deficiency anemia, there is a deficiency of iron which is essential for hemoglobin synthesis.
- This leads to the production of smaller red blood cells (microcytic) with reduced hemoglobin content (hypochromic).
- Consequently, red blood cells show a characteristic microcytic, hypochromic appearance on the peripheral smear.
- This morphological change reflects impaired hemoglobinization, a hallmark of iron deficiency anemia.
- Normocytic, normochromic cells are typical of early or mild anemia, while macrocytic cells are seen in vitamin B12/folate deficiency.
- Spherocytes are associated with hemolytic anemias, not iron deficiency.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Anaemia, Page 620.
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