A 33-year-old man is complaining of feeling thirsty all the time and passing more urine than usual. His physical examination is normal, except for a JVP at the sternal angle. His serum sodium is 150 mEq/L, glucose 120 mg/dL, and osmolality 315 mOsm/kg. The urine sodium is 20 mE/L and osmolality 260 mOsm/kg. Which of the following drugs is most likely to cause this disorder?
Nephrogenic DI can be caused by drugs such as lithium, metabolic factors, vascular disease, ureteral obstruction, and genetic factors.
A 22-year-old man has features of arm span greater than height, subluxed lenses, flattened corneas, and dilation of the aortic ring. Which of the following is the most likely diagnosis?
The severe form of Marfan syndrome is caused by a mutation in a single allele of the fibrillin gene (FBN1). The gene product is a major component of elastin-associated microfibrils. Long, thin extremities; ectopia lentis; and aortic aneurysms are the classical triad. Milder forms of the disease probably also occur but are hard to classify. Mutations in the FBN2 gene can also cause Marfan syndrome, but without aneurysms.
A 20-year-old woman is complaining of passing large amounts of urine. She is otherwise well and her physical examination is normal. The serum sodium is 140 mEq/L and the urinalysis is negative for protein and glucose. The urine sodium is 33 mEq/L, and urine osmolality is 268 mOsm/kg. She weighs 60 kg, and her 24-hour urine output is over 4 l. Which of the following is the most likely diagnosis?
In DM, there is an obligatory osmotic diuresis, but in DI there is lack of water resorption in the tubules. Both result in polyuria, but in DM, there will be substantial glucosuria as well. The large amount of urine output (usually >50 mL/ kg/day) is characteristic of polyuric states, such as DI, not a bladder problem. Psychogenic polydipsia is commonly seen in patients with psychiatric problems on medications.
Hypertriglyceridemia is usually secondary to DM or drugs, rather than a genetic disorder. It can be a normal response to caloric excess or alcohol ingestion and is common in the third trimester of pregnancy.
Subcutaneous xanthomas begin to appear at about age 20 and may involve Achillis tendons, elbows, and tibial tuberosities. Familial hypercholesterolemia may be monogenic or polygenic in its inheritance. The disorder is common, and heterozygous familial hypercholesterolemia is felt to affect 1 in 500 individuals. It can be secondary to other diseases such as hypothyroidism, nephrotic syndrome, or even porphyria. Xanthelasmas after the age of 50 are often not related to any dyslipidemia at all.
A 61-year-old woman with poorly controlled Type II diabetes is seen in follow-up. Her blood sugars are persistently elevated to levels greater than 200 mg/dL. On examination, she is obese, blood pressure 165/90 mm Hg, pulse 80/min, and there is sensory loss in the feet. Which of the following fasting lipid profiles is most likely to be consistent with her values?
In Type II diabetes, high levels of insulin and insulin resistance have multiple effects on lipid metabolism. These include increases in triglycerides, low HDL, and normal to high LDL. The high triglycerides respond to insulin therapy and to weight loss, while the low HDL responds to exercise.
A 27-year-old woman presents with feeling unwell ever since going on a high vitamin diet. She has dry skin, vomiting, headaches, and amenorrhea. Her examination and lab data are positive for hepatomegaly, splenomegaly, leukopenia, anemia, periosteal changes, sparse and coarse hair, and increased serum lipids. Which of the following is the most likely diagnosis?
Symptoms of vitamin A intoxication occur in infants or adults ingesting over 50,000 IU of vitamin A daily. The prognosis is good when vitamin A intake ceases. Rare occurrences of hypercalcemia with vitamin A intoxication have been reported.
Type III hyperlipoproteinemia
In the rare familial form, raised yellow plaques appear on palms and fingers, and reddish-yellow xanthomas occur on the elbows. This disorder is felt to be secondary to accumulation of abnormal chylomicron and very low-density lipoprotein (VLDL) remnants. It is probably due to inherited homozygous defects in Apo E-II structure.
A 54-year-old man comes to the emergency room with severe pain in his right toe. He has had less severe episodes in the past, which he always treated with pain medications. The toe is red, inflamed, and exquisitely sensitive to movement. Needle aspiration of the toe confirms uric acid crystals, and he is treated with oral indomethacin (NSAID). One month later, he remains symptom free, and allopurinol is recommended for prevention of this condition. Which of the following is the most likely mechanism of action of allopurinol?
Allopurinol inhibits the enzyme xanthine oxidase, resulting in decreased uric acid production. Allopurinol is particularly useful in the treatment of uric acid nephrolithiasis in gouty individuals. Even if the gouty individual has calcium oxalate stones, allopurinol may be helpful.
A 26-year-old man is evaluated for back pain and fatigue. He was previously healthy. On examination, he is pale, there is lumber spine tenderness, and an enlarged liver (18 cm). He is pancytopenic, and there is a vertebral fracture on lumbar x-rays. A bone marrow biopsy reveals infiltration with lipid-laden macrophages (Gaucher cells). Which of the following is the most likely diagnosis?
The diagnosis is inherited Gaucher’s disease since it is an autosomal recessive disorder. There is no acquired form of the disease. The glucocerebrosides are derived from lipid catabolites, from the membranes of senescent leukocytes and erythrocytes. Although the juvenile form may have severe neurologic symptoms (mental retardation, spasticity, ataxia), the adult form usually has no neurologic symptoms. Like Tay-Sachs, it is a lysosomal storage disease with a predilection for Ashkenazi Jews.
Triglycerides are over 150 and are raised by alcohol intake, estrogens, stress, insulin, and physical activity. Cholesterol levels are average or mildly elevated. HDL is usually low. Dietary therapy and the maintenance of ideal weight is the cornerstone of therapy.
The patient whose hands are shown in Fig. is developmentally delayed with a short, stocky build. Which of the following is the most likely diagnosis?
The deformity of the hands is due to short metacarpals. Other deformities include short metatarsals, round facies, and thickening of the calvarium. The syndrome is caused by target organ unresponsiveness to PTH, and was the first hormone resistance syndrome described
A 33-year-old man develops severe left flank pain that radiates to the front inguinal region. The pain eventually subsides after the passage of “sand-like” urine. A urinalysis reveals flat hexagonal plate like crystals (cystine). Which of the following statements about this condition is most likely true?
Cystinuria is commonly associated with hexagonal crystals in the urine. Cystine, lysine, arginine, and ornithine are excreted in great excess by patients homozygous for the disease. The tissues manifesting the transport defect of cystinuria are the proximal renal tubule and the jejunal mucosa. It is inherited as an autosomal recessive trait. Cystine kidney stones (1% of all renal stones) are the major clinical manifestation, and they are radiopaque.
A 53-year-old woman with chronic renal failure develops hyperphosphatemia and hypocalcemia. Which of the following findings is most likely associated with this electrolyte disturbance?
Hyperphosphatemia rarely causes any symptoms directly. Its secondary effects on calcium can result in hypocalcemic tetany or metastatic calcification. The usual cause of hyperphosphatemia is uremia.
A 19-year-old man has early fatigue and muscle cramps while playing sports. He is fine when walking or doing light levels of work. On examination, he appears well and the muscle strength in the proximal muscles is normal. There is no muscle fatigue with repetitive arm grip exercises. After an exercise stress test, his serum creatine kinase (CK) is elevated and lactate level is normal. Which of the following is the most likely diagnosis?
There are many types of glycogen storage diseases, each caused by a different enzymatic abnormality. The best known types of glycogen storage disease are those that have hepatichypoglycemic pathophysiology (e.g., von Gierke’s disease) or those that have muscle energy pathophysiology (McArdle’s disease). In McArdle’s symptoms usually develop in adulthood, and it is marked by cramps and muscle injury with strenuous exercise, but not with usual activities. Gaucher’s and Tay-Sachs disease are lysosomal storage diseases.
Which of the following laboratory values is consistent with the patient shown in Fig
The findings of hypocalcemia and hyperphosphatemia are the same as in hypoparathyroidism, but the serum PTH levels are appropriately increased. The normal urinary rise in cAMP does not occur when these patients are injected with exogenous (normal) PTH.
A 28-year-old woman with diabetes presents with lesions on her leg. They are not painful, and have a central depression and raised irregular margin. They are shown in Fig. Which of the following is the most likely diagnosis?
This lesion is more frequent in females and may antedate other clinical signs and symptoms of diabetes. The plaques are round, firm, and reddish-brown to yellow in color. They most commonly involve the legs but can also involve the hands, arms, abdomen, and head.
In the familial type 1 form, the defect is believed to be a deficiency of lipoprotein lipase activity. It is a rare autosomal recessive syndrome, and usually presents in childhood with typical eruptive xanthoma and abdominal pain secondary to acute pancreatitis. Secondary hyperchylomicronemia (diabetes, hypothyroidism, uremia) is a much more common syndrome.
A 25-year-old man requests cholesterol screening because of a family history of premature coronary artery disease (CAD). His lipid levels reveal an elevated total and LDL cholesterol. The high-density lipoprotein (HDL) and triglyceride values are normal. His physical examination is completely normal. Which of the following is the most common cause of genetic dyslipidemia?
Familial combined hyperlipidemia has an incidence of 1/100. It is an autosomal dominant disorder and different affected family members may display different dyslipidemic phenotypes. Familial hypercholesterolemia (1/500) and familial defective Apo B (1/1000) are also common. The other two disorders (Apo C-II deficiency and lipoprotein lipase deficiency) are extremely rare.
A 50-year-old man presents with feeling tired and unsteady on his feet. He has a poor appetite and has lost 10 lb. On examination, he appears cachectic, his heart and lungs are normal, but his liver span is 18 cm. His lab tests show a very low magnesium level (0.7 mEq/L). On further questioning, he reports drinking heavily since losing his job. Which of the following is the most likely explanation for his low magnesium level?
Magnesium deficiency is most commonly due to alcoholism. Renal loss and malabsorption are also common causes. Magnesium deficiency is not seen in hypervitaminosis E. Causes of magnesium deficiency also include milk diets in infants, the diuretic phase of acute tubular necrosis, chronic diuretic therapy, acute pancreatitis, and inappropriate antidiuretic hormone. The symptoms of hypomagnesemia include anorexia, nausea, tremor, and mood alteration. Symptoms can also be caused by the associated hypocalcemia or hypokalemia.
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