The clinical picture of this patient was dominated by nonspecific constitutional symptoms, such as fatigue, malaise, vomiting, abdominal cramps, and weight loss. He had no history of maculopapular rashes, erythema nodosum, arthritis, chronic lymphocytopenia, hepatomegaly, splenomegaly, lymphadenopathy, or uveitis. He also did not have any coughing or exertional dyspnea. The child did have vomiting and polyuria, which were caused by hypercalcemia.
The renal biopsy specimen indicated acute tubulointerstitial nephritis associated with tubular calcium deposits, without glomerular abnormalities. In addition, the chest radiograph demonstrated combined hilar lymphadenopathy and reticulonodular interstitial infiltrates in the upper lung zone (Figure 2).
The chest radiography findings, when considered along with the hypercalcemia, rash, and renal biopsy results, are consistent with stage 2 radiographic sarcoidosis.
Hypercalcemia associated with hypercalciuria and nephrocalcinosis is rare in childhood and may have many causes. The most common cause is iatrogenic, followed by idiopathic infantile hypercalcemia in its mild or severe form (Williams syndrome).
Vitamin D intoxication is a rare cause of clinically manifested hypercalcemia, but it is associated with significant morbidity. It may be caused by endogenous synthesis of 1,25-dihydroxyvitamin D from subcutaneous fat necrosis and granulomatous disease or by excessive exogenous vitamin D intake. Hypercalcemia may also result from primary hyperparathyroidism or from increased levels of parathyroid hormone-related protein caused by certain malignancies. Finally, hypercalcemia may occur in patients with Jansen syndrome, hypophosphatemia, vitamin A intoxication, or blue-diaper syndrome, or it may occur in association with use of certain medications, most notably hydrochlorothiazide and other thiazide diuretics.[1,2]
An intact parathyroid hormone (PTH) level at the time of hypercalcemia is pivotal in narrowing the differential diagnosis. If the PTH level is high, the child must be thoroughly investigated for the cause of hyperparathyroidism and may require urgent surgical intervention. If the PTH level is low (as it was in this patient), additional calciotropic hormones may be assayed if appropriate testing is available. Identifying the abnormal calciotropic hormone might allow diagnosis of the specific cause, elucidation of the mechanism for the hypercalcemia, and optimal treatment.
Sarcoidosis is a multisystem disorder characterized by an increased cellular immune response to an unknown antigen and the formation of noncaseating granulomas in affected tissues. Although the lungs and lymph nodes are the predominant sites affected by sarcoidosis (75%-90%), other organs, such as the eyes, bone marrow, kidneys, liver, and spleen, may also be involved.[2,3] Cases of extrapulmonary sarcoidosis affecting the kidneys are rare; most such cases present with nephrocalcinosis or nephrolithiasis (3.6%). Renal failure is an extremely uncommon manifestation.[4,5]
Hypercalcemia in sarcoidosis is uncommon, occurring in approximately 10% of cases.[2,3] It is usually caused by the autonomous production of 1,25-dihydroxyvitamin D (calcitriol) by macrophages within the granuloma. These macrophages can convert 25-hydroxyvitamin D, produced by the liver, into calcitriol by possessing the 1-alpha-hydroxylase enzyme. Calcitriol then travels to the intestinal cells and promotes luminal absorption of calcium and phosphate into the circulation. Hypercalcemia is accompanied by hypercalciuria and, eventually, nephrocalcinosis (as seen in this case). Hypercalcemia may also eventually cause renal failure both by causing dehydration and by inducing renal vasoconstriction, thereby reducing the glomerular filtration rate.
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