Correspondence
Case 9-1999: Wegener's Granulomatosis
N Engl J Med 1999; 341:541-542August 12, 1999
- Article
To the Editor:
Case 9-1999 (March 25 issue)1 involves a 75-year-old woman with Wegener's granulomatosis. Dr. Schwartz's discussion of the neurologic aspects of this patient's illness is scholarly. However, he fails to address important parts of the history and laboratory findings. The patient had profound muscular weakness: “Two weeks before admission, she fell in the bathtub and remained there all night because of generalized weakness. One day before admission, she again fell, striking her occiput and lying on the floor for two hours because of diffuse weakness.” Laboratory data (presented in Table 2 of the report) included serum calcium and phosphorus levels of 6.7 and 1.7 mg per deciliter, respectively. These data are pathognomonic for profound vitamin D deficiency, or osteomalacia. The diagnosis would have been made by the demonstration of an abnormally low blood level of 25-hydroxyvitamin D and would have been confirmed by an elevated blood level of intact parathyroid hormone. Severe muscular weakness is part of the clinical picture in this condition.2 The patient may also have had diffuse bone pain or tenderness.
The pathophysiology of vitamin D deficiency is well established. In the absence of vitamin D, absorption of calcium from the gut, both ingested calcium and calcium in the enteric circulation, ceases. The parathyroid glands elaborate increasing amounts of parathyroid hormone in an effort to maintain the blood calcium level in the normal range through bone resorption. Secondary hypophosphatemia develops as the hormone prevents phosphate reabsorption by renal tubules. Late in the course of the disease, when all bone surfaces are covered with unmineralized osteoid, maintenance of the blood calcium level fails. At this time, the blood calcium level falls, resulting in the findings noted in the case under discussion.
Vitamin D deficiency is not uncommon in the elderly population of the United States3 (and unpublished data). The deficiency frequently escapes notice, since the condition of hospitalized patients slowly improves if they are ingesting a multivitamin that includes vitamin D or consuming the usual hospital diet, which contains vitamin D in milk and in deep-sea fish. The improvement is usually ascribed to the successful treatment of the illness for which they have been hospitalized.
The diagnosis of osteomalacia, or vitamin D deficiency, should have been added to the diagnosis of Wegener's granulomatosis in this case. In elderly patients, the principle of Ockham's razor is frequently inapplicable.
3 ReferencesUriel S. Barzel, M.D.
Montefiore Medical Center, Bronx, NY 104671
Case Records of the Massachusetts General Hospital (Case 9-1999)
Full Text | Web of Science | Medline2
Barzel US . Vitamin D deficiency: a risk factor for osteomalacia in the aged. J Am Geriatr Soc 1983;31:598-601
Web of Science | Medline3
Thomas MK ,Lloyd-Jones DM ,Thadhani RI , et al. Hypovitaminosis D in medical inpatients. N Engl J Med 1998;338:777-783
Full Text | Web of Science | Medline
Author/Editor Response
Dr. Schwartz replies:
To the Editor: Dr. Barzel's comments on vitamin D deficiency in the elderly are appreciated. In this case, however, the chemical values were obtained on the 17th hospital day, after progressive obtundation, probably poor oral intake, and presumed therapy with intravenous fluids. As shown in Table 2 of the article, the total serum calcium level of 6.7 mg per deciliter was accompanied by a decreased serum albumin level (1.8 g per deciliter). Assuming a normal pH, about 0.8 mg of calcium is bound per gram of albumin, resulting in a normal level of ionized calcium, 5.3 mg per deciliter, in this patient. Since the physical examination did not suggest a myopathy, it is not obvious that vitamin D deficiency accounted for the preadmission history of diffuse weakness.
William J. Schwartz, M.D.
University of Massachusetts Medical School, Worcester, MA 01655
