HISTORY — A 20-year-old man with end-stage renal disease and a painful, violaceous, plaque-like skin eruption over the lower extremities was admitted to the hospital. His past medical history was remarkable for a rapidly progressive glomerulonephritis, an unsuccessful cadaveric renal transplant, and poorly controlled hypertension. Shortly after admission, he developed respiratory distress requiring mechanical ventilation. Over the next few weeks, his skin lesions spread to the abdomen and back and became ulcerative and necrotic, forming eschars. The patient eventually required tracheotomy for chronic ventilator support.
HOSPITAL COURSE — Later in the hospitalization, the serum calcium increased to 14 mg/dL, and a serum mid-chain parathyroid hormone level was increased at 246 pg/mL. A skin biopsy revealed diffuse subcutaneous and vascular calcification with in situ thrombosis. A bone scan is shown
PHYSICAL EXAMINATION — Afebrile; respirations 24 on the ventilator; blood pressure 100/90. General: chronically ill appearing. Chest: scattered rhonchi. Cardiac examination: II/VI systolic ejection murmur at the left sternal border. Skin: multiple plaque-like lesions with areas of necrosis, ulceration, and eschars.
LABORATORY FINDINGS — Hct 19.7 percent; WBC 14,500/mm3. Na+ 125 mEq/L; K+ 3.6 mEq/L; Cl - 89 mEq/L; HCO3 -16 mEq/L; BUN 95 mg/dL; creatinine 10.3 mg/dL; phosphate 6.5 mg/dL; calcium 7.2 mg/dL. Chest radiograph : diffuse infiltrates. Right heart catheterization: PAOP 12 mmHg; CI 3.7 L/min/m2; SVR 1170 dyne sec cm -5.
QUESTION — What is the cause of the patient's respiratory failure?