Examkin

Soru

Zorluk: Çok zorNephrology

Match each of the following patient presentations, which are characterized by specific acid-base and electrolyte derangements (Left), with the precise underlying cellular or transporter defect (Right).

  • A 24-year-old female presents with chronic fatigue. Laboratory evaluation reveals a K+K^+ of 2.8 mEq/L, Mg2+Mg^{2+} of 1.2 mEq/L, and HCO3−HCO_3^- of 32 mEq/L. Her blood pressure is 110/70 mm Hg. A 24-hour urine collection shows a calcium-to-creatinine ratio of 0.05.Loss-of-function mutation affecting the thiazide-sensitive Na+Na^+-Cl−Cl^- cotransporter in the distal convoluted tubule.
  • A 19-year-old male is evaluated for severe, treatment-resistant hypertension with a blood pressure of 175/110 mm Hg. Laboratories demonstrate a K+K^+ of 2.6 mEq/L and HCO3−HCO_3^- of 31 mEq/L. Both plasma renin activity and serum aldosterone concentrations are markedly suppressed.Gain-of-function mutation preventing ubiquitin-mediated degradation of the epithelial sodium channel (ENaCENaC) in the collecting duct.
  • A 38-year-old female presents with recurrent nephrolithiasis and is found to have bilateral medullary nephrocalcinosis on imaging. Laboratories show a K+K^+ of 3.1 mEq/L, Cl−Cl^- of 112 mEq/L, and HCO3−HCO_3^- of 16 mEq/L. Her fasting morning urine pHpH is 6.8.Defective secretion of H+H^+ by the apical H+H^+-ATPase pump in the alpha-intercalated cells of the collecting duct.
  • A 55-year-old male with multiple myeloma presents with bone pain. Laboratories reveal a K+K^+ of 2.9 mEq/L and HCO3−HCO_3^- of 15 mEq/L with a normal serum anion gap. Urinalysis demonstrates significant glycosuria despite a simultaneous serum glucose of 90 mg/dL.Generalized impairment of solute transport, including Na+Na^+/glucose cotransport and HCO3−HCO_3^- reabsorption, in the proximal convoluted tubule.

Cevap

The correct matches align the hypocalciuric normotensive patient with the DCT NCCT defect, the hypertensive patient with suppressed aldosterone to ENaC hyperactivity, the patient with nephrocalcinosis and alkaline urine to impaired alpha-intercalated cell H+ secretion, and the multiple myeloma patient with normoglycemic glycosuria to proximal convoluted tubule dysfunction.
Arriving at the correct diagnosis for each tubulopathy requires synthesizing the acid-base status, serum electrolytes, blood pressure, and specific urinary findings (calcium excretion, glucose, pH). Once the clinical syndrome is accurately identified, it maps precisely to a unique anatomical location and molecular transporter defect within the nephron.

Adım Adım Çözüm

1
Evaluate the patient presenting with normotension, hypokalemia, metabolic alkalosis, and hypocalciuria.
Identify Gitelman syndrome, which maps to a defect in the distal convoluted tubule (NCCT).
The unique combination of salt-wasting (hypokalemia, alkalosis) with normotension and low urine calcium uniquely points to a distal convoluted tubule defect rather than a loop of Henle defect (Bartter syndrome).
2
Evaluate the patient with severe hypertension, hypokalemic metabolic alkalosis, and suppressed renin/aldosterone.
Identify Liddle syndrome, which maps to a gain-of-function mutation in ENaC.
If aldosterone is suppressed despite features of hyperaldosteronism, the defect must be constitutive activation of the downstream sodium channel in the collecting duct.
3
Evaluate the patient with a non-anion gap metabolic acidosis, hypokalemia, nephrocalcinosis, and fasting urine pH of 6.8.
Identify Type 1 (distal) RTA, which maps to defective H+ secretion by alpha-intercalated cells.
The inability to acidify urine below a pH of 5.5, combined with calcium phosphate stones, localizes the defect precisely to the distal nephron's proton pumps.
4
Evaluate the patient with multiple myeloma presenting with non-anion gap metabolic acidosis, hypokalemia, and normoglycemic glycosuria.
Identify Fanconi syndrome (Type 2 proximal RTA), which maps to generalized proximal convoluted tubule dysfunction.
Glycosuria in the absence of hyperglycemia implies a failure of the proximal tubule's Na+/glucose cotransporter, which often accompanies a failure to reabsorb bicarbonate in Fanconi syndrome.

Anahtar Kavram

Pathophysiology and localization of renal tubular defects, including renal tubular acidoses and inherited tubulopathies.
Tahmini Süre:3m 0s
Bu soruyu puanla

Konular

Nephrology

Bu konudan daha fazla soru