A 28-year-old woman presents with abdominal pain, diarrhea, and rectal bleeding. She has a history of similar episodes in the past. What is the most likely diagnosis?

Correct Answer: A

Rationale: The correct answer is A: Ulcerative colitis. This chronic inflammatory condition affects the colon and rectum, leading to symptoms like abdominal pain, diarrhea, and rectal bleeding. The patient's recurrent episodes and history of similar symptoms point towards ulcerative colitis. Irritable bowel syndrome (choice B) typically presents with abdominal pain, bloating, and changes in bowel habits but not rectal bleeding. Celiac disease (choice C) presents with gastrointestinal symptoms after consuming gluten. Diverticulitis (choice D) presents with localized abdominal pain and fever due to inflammation or infection of the diverticula, not typically with rectal bleeding.

Correct Answer: A

Rationale: The most likely diagnosis for a 40-year-old woman presenting with fatigue, polyuria, polydipsia, hyperglycemia, and ketonuria is Type 1 diabetes mellitus. 1. Age: Type 1 diabetes commonly presents at a younger age. 2. Symptoms: Polyuria, polydipsia, fatigue are classic symptoms of uncontrolled diabetes. 3. Laboratory tests: Hyperglycemia and ketonuria indicate insulin deficiency. 4. Clinical presentation: Presence of ketonuria suggests metabolic derangement due to lack of insulin. In summary, Type 1 diabetes is the correct choice due to the age of the patient, symptoms, laboratory findings, and clinical presentation. Diabetes insipidus (choice C) presents with polyuria and polydipsia but lacks hyperglycemia and ketonuria. Type 2 diabetes (choice B) typically presents at an older age and rarely with ketonuria. Hyperthyroidism (choice D)

Correct Answer: A

Rationale: The most likely diagnosis is A: Primary biliary cirrhosis. Rationale: 1. Pruritus, jaundice, and xanthomas are classic symptoms of cholestatic liver disease. 2. Elevated cholesterol and alkaline phosphatase levels are characteristic of primary biliary cirrhosis. 3. Primary biliary cirrhosis is an autoimmune disease affecting small bile ducts, leading to liver damage. 4. Primary sclerosing cholangitis (B) presents with similar symptoms but typically affects larger bile ducts. 5. Gallstones (C) could cause jaundice but would not explain the elevated cholesterol levels. 6. Pancreatic cancer (D) may present with jaundice but is less likely given the specific lab findings.

Correct Answer: B

Rationale: The most likely diagnosis is Addison's disease (Choice B) because the symptoms match adrenal insufficiency. The low cortisol levels indicate adrenal cortex dysfunction, leading to fatigue and weight loss. Hyponatremia and hyperkalemia result from mineralocorticoid deficiency. Hyperpigmentation occurs due to elevated ACTH levels stimulating melanin production in Addison's. Cushing's syndrome (Choice A) presents with high cortisol levels, opposite to the low levels seen here. Hypothyroidism (Choice C) does not typically cause hyponatremia or hyperkalemia. Pheochromocytoma (Choice D) manifests with hypertension and catecholamine excess, not seen in this case.

Correct Answer: B

Rationale: The most likely diagnosis for the 70-year-old woman is Addison's disease. The symptoms of fatigue, anorexia, weight loss, darkened skin, along with hyponatremia, hyperkalemia, and low cortisol levels indicate adrenal insufficiency. Addison's disease is characterized by inadequate production of cortisol and aldosterone by the adrenal glands. The darkening of the skin, known as hyperpigmentation, is a classic sign of Addison's due to increased ACTH levels stimulating melanin production. In contrast, Cushing's syndrome presents with weight gain, hypertension, and high cortisol levels. Hypothyroidism typically presents with weight gain, cold intolerance, and constipation. Pheochromocytoma presents with hypertension, palpitations, and headaches due to excess catecholamine production. Therefore, the correct diagnosis in this case is Addison's disease.