Volume 121 Number 4
olism: disorders of calcium homeostasis. J PEDIATR 1976;88: 177-99. 3. Suh SM, Tashijan AH, Matsuo N, Parkinson DR, Fraser D. Pathogenesi s of hypocalcemia in primary hypomagnesemia: normal end-organ responsiveness to parathyroid hormone, impaired parathyroid gland function. J Clin Invest 1973;52:15360. 4. Bettinelli A, Bianchetti MG, Girardin E, et al. Use of calcium excretion values to distinguish two forms of primary renal tubular hypokalemic alkalosis: Bartter and Gitelman syndromes. J PEDIATR 1992;120:38-43.
Renal abnormalities associated with Williams syndrome To the Editor. We read the article "Spectrum of Renal Anomalies in Patients With Williams Syndrome," by Ingelfinger and Newburger, l with great interest. They suggested that renal abnormalities are not uncommon in association with Williams syndrome and therefore recommended that patients with this syndrome undergo specific screening for renal structure and function as well as continued monitoring of renal function and blood pressure. We also retrospectively studied the renal abnormalities in eight children with Williams syndrome whom we saw between 1975 and 1992; four were male. The mean age of these patients at the time of review was 10 years (range birth to 16 years of age), and the mean period of observation was 6 years (range 6 months to 12 years). We evaluated blood urea nitrogen and serum creatinine concentrations, urinalysis results, blood pressure, and results of intravenous pyelography and arteriography. In two of the eight patients, intravenous pyetography and arteriography were not done. Systemic hypertension was present in two of the eight patients; these two were reported previously2 and had renal artery stenosis. One patient with a single kidney had an activated renin-angiotensin system, although his renal function was normal. Neither renal dysfunction nor activation of the renin-angiotensin system was detected in the other. The other six patients did not have any renal abnormalities. The age distribution of our patients was lower than that of the patients described by Ingelfinger and Newburger (median age 19 years). The discrepancy in the incidence of renal abnormalities could mean that Williams syndrome is a progressive vascular disease resulting in kidney involvement. In fact, one patient whom we reported previously has progressive systemic arterial stenosis. We agree that it is important to evaluate the renal abnormalities in children with Williams syndrome in the long term. Yoshiharu Suzuki, MD Shinjiro Shimazaki, MD Kazunari Kaneko, MD Toshihiro Ino, MD Keifiro Yabuta. MD Department of Pediatrics Juntendo University School of Medicine Hongo 3-1-1, Bunkyo-ku, Tokyo, Japan 9/35/39983
Editorial correspondence
667
REFERENCES
1. Ingelfinger JR, Newburger JW. Spectrum of renal anomalies in patients with Williams syndrome. J PEDIATR 1991;119: 771-3. 2. Ino T, Akimoto K, Nishimoto K, et al. Progressive vascular lesion in Williams-Beuren syndrome. Pediatr Cardiol 1988; 9:55-8.
Diagnostic tests for acyl-coenzyme A dehydrogenase deficiency To the Editor." Parini et al. (J PEDIATR 1991;119:77-80) performed both 22-hour fasting and 6-hour fat loading tests, preceded by a 10-hour fast, in a 2-year-old patient with long-chain acyl-coenzyme A dehydrogenas e (LCAD) deficiencY. The authors recommend the use of these tests to facilitate identification of patients with B-oxidation defects. They justify their choice of procedure by claiming that the risk is less than that of a patient with an undiagnosed defect who is waiting at home for enzymatic test results before treatment can be initiated. The importance of rapid diagnosis in these patients is undebatable, but the danger of fasting for relatively prolonged periods precludes such studies as routine diagnostic tools. A patient with medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency died after a similar fasting test.l Monitoring plasma glucose levels is an insufficient safety measure because serious clinical symptoms might develop in MCAD-deficient patients who yet have normoglycemia.2, 3 Normoglycemia does not protect against9 as was our experience with a 14-month-old patient with LCAD deficiency who was hospitalized with an intercurrent infection. She was treated with an intravenously administered dextrose solution for 2 days but, despite normoglycemia, became comatose and required hemodialysis. A recently described method for estimating the B-oxidation pathway by using [9,10-3H]myristic acid oxidation can facilitate the treatment of most patients with suspected B-0xidation defects. 4 The assay can be performed .on leukocytes, and the results are available within hours. In our opinion, this assay should be used instead of the in vivo tests in all patients with susPected B-oxidation defects. If further localization of the defect is required, a 4-hour fast preceding the fat-loading tests is probably sufficient. 5 In our experience, patients with LCAD and MCAD deficiencies respond favorably to a high-carbohydrate, low-fat diet regardless of its fatty acid composition as long as frequent feeding, including a late-night high-carbohydrate drink, is maintained. Therefore patients with these defects can be treated in the fashion described above until a definitive diagnosis is available. Orly N. Elpeleg, MD Metabolic Unit Shaare-Zedek Medical Center Jerusalem 91031, Israel 9/35/39984
olism: disorders of calcium homeostasis. J PEDIATR 1976;88: 177-99. 3. Suh SM, Tashijan AH, Matsuo N, Parkinson DR, Fraser D. Pathogenesi s of hypocalcemia in primary hypomagnesemia: normal end-organ responsiveness to parathyroid hormone, impaired parathyroid gland function. J Clin Invest 1973;52:15360. 4. Bettinelli A, Bianchetti MG, Girardin E, et al. Use of calcium excretion values to distinguish two forms of primary renal tubular hypokalemic alkalosis: Bartter and Gitelman syndromes. J PEDIATR 1992;120:38-43.
Renal abnormalities associated with Williams syndrome To the Editor. We read the article "Spectrum of Renal Anomalies in Patients With Williams Syndrome," by Ingelfinger and Newburger, l with great interest. They suggested that renal abnormalities are not uncommon in association with Williams syndrome and therefore recommended that patients with this syndrome undergo specific screening for renal structure and function as well as continued monitoring of renal function and blood pressure. We also retrospectively studied the renal abnormalities in eight children with Williams syndrome whom we saw between 1975 and 1992; four were male. The mean age of these patients at the time of review was 10 years (range birth to 16 years of age), and the mean period of observation was 6 years (range 6 months to 12 years). We evaluated blood urea nitrogen and serum creatinine concentrations, urinalysis results, blood pressure, and results of intravenous pyelography and arteriography. In two of the eight patients, intravenous pyetography and arteriography were not done. Systemic hypertension was present in two of the eight patients; these two were reported previously2 and had renal artery stenosis. One patient with a single kidney had an activated renin-angiotensin system, although his renal function was normal. Neither renal dysfunction nor activation of the renin-angiotensin system was detected in the other. The other six patients did not have any renal abnormalities. The age distribution of our patients was lower than that of the patients described by Ingelfinger and Newburger (median age 19 years). The discrepancy in the incidence of renal abnormalities could mean that Williams syndrome is a progressive vascular disease resulting in kidney involvement. In fact, one patient whom we reported previously has progressive systemic arterial stenosis. We agree that it is important to evaluate the renal abnormalities in children with Williams syndrome in the long term. Yoshiharu Suzuki, MD Shinjiro Shimazaki, MD Kazunari Kaneko, MD Toshihiro Ino, MD Keifiro Yabuta. MD Department of Pediatrics Juntendo University School of Medicine Hongo 3-1-1, Bunkyo-ku, Tokyo, Japan 9/35/39983
Editorial correspondence
667
REFERENCES
1. Ingelfinger JR, Newburger JW. Spectrum of renal anomalies in patients with Williams syndrome. J PEDIATR 1991;119: 771-3. 2. Ino T, Akimoto K, Nishimoto K, et al. Progressive vascular lesion in Williams-Beuren syndrome. Pediatr Cardiol 1988; 9:55-8.
Diagnostic tests for acyl-coenzyme A dehydrogenase deficiency To the Editor." Parini et al. (J PEDIATR 1991;119:77-80) performed both 22-hour fasting and 6-hour fat loading tests, preceded by a 10-hour fast, in a 2-year-old patient with long-chain acyl-coenzyme A dehydrogenas e (LCAD) deficiencY. The authors recommend the use of these tests to facilitate identification of patients with B-oxidation defects. They justify their choice of procedure by claiming that the risk is less than that of a patient with an undiagnosed defect who is waiting at home for enzymatic test results before treatment can be initiated. The importance of rapid diagnosis in these patients is undebatable, but the danger of fasting for relatively prolonged periods precludes such studies as routine diagnostic tools. A patient with medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency died after a similar fasting test.l Monitoring plasma glucose levels is an insufficient safety measure because serious clinical symptoms might develop in MCAD-deficient patients who yet have normoglycemia.2, 3 Normoglycemia does not protect against9 as was our experience with a 14-month-old patient with LCAD deficiency who was hospitalized with an intercurrent infection. She was treated with an intravenously administered dextrose solution for 2 days but, despite normoglycemia, became comatose and required hemodialysis. A recently described method for estimating the B-oxidation pathway by using [9,10-3H]myristic acid oxidation can facilitate the treatment of most patients with suspected B-0xidation defects. 4 The assay can be performed .on leukocytes, and the results are available within hours. In our opinion, this assay should be used instead of the in vivo tests in all patients with susPected B-oxidation defects. If further localization of the defect is required, a 4-hour fast preceding the fat-loading tests is probably sufficient. 5 In our experience, patients with LCAD and MCAD deficiencies respond favorably to a high-carbohydrate, low-fat diet regardless of its fatty acid composition as long as frequent feeding, including a late-night high-carbohydrate drink, is maintained. Therefore patients with these defects can be treated in the fashion described above until a definitive diagnosis is available. Orly N. Elpeleg, MD Metabolic Unit Shaare-Zedek Medical Center Jerusalem 91031, Israel 9/35/39984
