Transient Hypophosphatemia: A Dangerous Event in Multiple My
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This is the case of a 56-year-old Hispanic woman with a past medical history of arterial hypertension, type 2 diabetes mellitus, and chronic anemia who was transferred from a community medical clinic to our institution for management of symptomatic anemia, severe hypercalcemia, and renal failure. Upon evaluation at our institution, the patient stated that, for the last three months, she had been experiencing fatigue, generalized weakness, back pain, decreased appetite, and unquantified weight loss. Moreover, the day prior to admission, she had an episode of lightheadedness followed by loss of consciousness for which she was taken to the community medical clinic for evaluation. Upon arrival to our institution, her blood pressure was 161/76 mmHg with a heart rate of 78 bpm, respiratory rate of 18 rpm, the temperature of 36.5°C, and peripheral oxygen saturation of 99% at room air. The physical examination provided a remarkable perspective for an acutely ill appearance, generalized paleness, and dry oral mucosa.

Initial laboratories were also remarkable for normocytic normochromic anemia of 6.5 g/dL (12.0–14.0), albumin-corrected calcium of 13.8 mg/dL (8.8–10.3), and elevated creatinine of 6.7mg/dL (0.60–1.10) with a glomerular filtration rate of 7min/mL. 25-Hydroxyvitamin D was within normal limits at 38.1 ng/ml (30.0–100.0), whereas 1,25-dihydroxy vitamin D was low at 8. pg/mL (19.9–79.3). Notwithstanding, the patient had a normal phosphorus level of 2.50 mg/dL (2.40–4.20) and normal intact parathyroid hormone in 25 pg/mL (11–67). Finally, radiographic images disclosed multiple skeletal lytic lesions. In light of such clinical presentation, the patient was admitted into the internal medicine ward with an ongoing diagnosis of symptomatic anemia, acute renal failure, and moderate hypercalcemia.

The results from bone marrow biopsy were consistent with high-risk IgG/kappa multiple myeloma, the reason why she was started on chemotherapy with cyclophosphamide, bortezomib, and dexamethasone (CyBorD). At this point, it was remarkable that the patient continued with corrected hypercalcemia of 11 mg/dL (8.8–10.3) and developed hypophosphatemia of 1.7mg/dL (2.40–4.20). During the second week of hospitalization, the patient suffered a pathological fracture of the right humerus for which a single dose of zoledronic acid was administered. Therefore, based on the evidence of the pathological fracture, the patient was evaluated by radiation-oncology specialists and was treated with external beam radiotherapy (IMRT technique) up to about the total dose of 4000 cGy.

In view of the persistent hypophosphatemia and the new laboratory results, it's considered secondary hyperparathyroidism, and pseudohypercalcemia as the etiology of hypophosphatemia. The patient was initiated on calcitriol, and as a result, electrolytes normalized. She was discharged after 30 days of hospitalization, with remarkable laboratories at the moment of discharge for normal renal function with creatinine at 0.96 mg/dL (0.6–1.10), albumin-corrected calcium at 9.9 mg/dL (8.8–10.3), and phosphorus at 4.70 mg/dL (2.40–4.20). Eventually, the patient was successfully treated with an autologous stem cell transplant with excellent response.

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