S. aureus is the most common cause of localized folliculitis. Enteropathy-type T cell lymphoma most commonly occurs in the jejunum or the ileum. Nearly 40% of tourists to endemic regions of Latin America, Africa, and Asia develop so-called traveler’s diarrhea, most commonly due to enterotoxigenic or enteroaggregative Escherichia coli as well as to Campylobacter , Shigella , Aeromonas , norovirus, Coronavirus, and Salmonella, Institutionalized persons: Infectious diarrhea is one of the most frequent categories of nosocomial infections in many hospitals and long-term care facilities; the causes are a variety of micro-organisms but most commonly C. difficile, Gastrinoma , one of the most common neuroendocrine tumors, most typically presents with refractory peptic ulcers, but diarrhea occurs in up to one-third of cases and may be the only clinical manifestation in 10%, One of the most common causes of chronic diarrhea in adults is lactase deficiency , which affects three-fourths of non-whites worldwide and 5–30% of persons in the United States, Intraluminal maldigestion:This condition most commonly results from pancreatic exocrine insufficiency, which occurs when > 90% of pancreatic secretory function is lost, Mucosal malabsorption occurs from a variety of enteropathies, but it most commonly occurs from celiac disease, Further evaluation of osmotic diarrhea should include tests for lactose intolerance and magnesium ingestion, the two most common causes, Peptic ulcers are the most common cause of upper gastrointestinal sources of bleeding(UGIB), accounting for up to ∼ 50% of cases; an increasing proportion is due to non-steroidal anti-inflammatory drugs (NSAIDs), with the prevalence of Helicobacter pylori decreasing. Cholestatic hepatitis has been reported with chlorpromazine, imipramine, tolbutamide, sulindac, cimetidine, and erythromycin estolate, Choledocholithiasis is the most common cause of extrahepatic cholestasis, The most common etiologies of isolated glomerular hematuria are IgA nephropathy, hereditary nephritis, and thin basement membrane disease, The syndrome of inappropriate antidiuresis is the most common cause of euvolemic hyponatremia, Syndrome of inappropriate antidiuresis(SIAD) also occurs with malignancies, most commonly with small cell lung carcinoma (75% of cases of malignancy-associated SIAD), SIAD is also a common complication of certain drugs, most commonly the selective serotonin reuptake inhibitors (SSRIs), Although redistribution and reduced tissue uptake can acutely cause hyperkalemia, a decrease in renal K+ excretion is the most common underlying cause, Delay in treatment is one of the most common causes of mortality with toxic alcohol poisoning, Chronic hypercalcemia is most commonly caused by primary hyperparathyroidism, as opposed to the second most common etiology of hypercalcemia, an underlying malignancy, Although there are many potential causes of hypocalcemia, impaired PTH or vitamin D production are the most common etiologies, In adults, hypoparathyroidism most commonly results from inadvertent damage to all four glands during thyroid or parathyroid gland surgery, Hyporeninemic hypoaldosteronism typically causes non-AG metabolic acidosis, most commonly in older adults with diabetes mellitus or tubulointerstitial disease and renal insufficiency, Chronic respiratory alkalosis is the most common acid-base disturbance in critically ill patients and, when severe, portends a poor prognosis, Salicylates are the most common cause of drug-induced respiratory alkalosis as a result of direct stimulation of the medullary chemoreceptor, The most common organic cause of erectile dysfunction (ED) is a disturbance of blood flow to and from the penis, Oral phosphodiesterase type 5 inhibitor therapy is the most commonly employed therapy for th treatmnt of erectile dysfunction (ED), PCOS is the most common cause of ovarian androgen excess, Nonclassic congenital adrenal hyperplasia (CAH) is most commonly due to 21-hydroxylase deficiency but also can be caused by autosomal recessive defects in other steroidogenic enzymes necessary for adrenal corticosteroid synthesis, Superficial spreading melanoma is the most common type of melanoma, Chronic low-grade irritant dermatitis is the most common type of Irritant contact dermatitis(ICD), and the most common area of involvement is the hands, The most common cause of Allergic contact dermatitis(ACD) is exposure to plants, especially to members of the family Anacardiaceae, including the genus Toxicodendron, Nummular eczema occurs more frequently in men and is most commonly seen in middle age, The most common location of seborrheic dermatitisis is the scalp, where it may be recogized as severe dandruff, The most common variety of psoriasis is called plaque-type.The most commonly involved areas are the elbows, knees, gluteal cleft, and the scalp, Guttate psoriasis (eruptive psoriasis) is most common in children and young adults, Filiform warts are most commonly seen on the face, neck, and skinfolds and present as papillomatous lesions on a narrow base. B cell CLL/small lymphocytic lymphoma represents the most common lymphoid leukemia, and when presenting as a lymphoma, it accounts for ~7% of non-Hodgkin’s lymphomas, The most common treatments for patients with typical B cell CLL/small lymphocytic lymphoma have been chlorambucil or fludarabine, alone or in combination, The most common presentation of mantle cell lymphoma is with palpable lymphadenopathy, frequently accompanied by systemic symptoms, The most common presentation for follicular lymphoma is with new, painless lymphadenopathy, Diffuse large B cell lymphoma is the most common type of non-Hodgkin’s lymphoma, representing approximately one-third of all cases. The streamlined outline format includes tables diagrams clinical photos and radiographs for a concentrated efficient review. The most commonly affected nerve trunk in leprosy is the ulnar nerve at the, elbow, whose involvement results in clawing of the fourth and fifth fingers, loss of dorsal interosseous musculature in the affected hand, and loss of sensation in these distributions, Meningovascular syphilis reflects meningitis together with inflammatory vasculitis of small, medium, or large vessels. Thalassemias are the most common genetic disorders in the world, affecting nearly 200 million people worldwide. Most of the patients involved have uncontrolled peritonsillar infections progressing to septic cervical venous thrombophlebitis (Lemierre’s syndrome) and resulting in hematogenous dissemination with a predilection for the joints.