LAUSR

To the Editor: Calcinosis cutis is a rare disease characterized by depositions of amorphous calcium salts in the skin. Metastatic calcification is often responsible for this situation. In patients undergoing hemodialysis, high levels of calcium and phosphorus due to hyperparathyroidism are the most important causes of calcinosis cutis. Primary hyperoxaluria is an unusual hereditary metabolic disorder characterized by abnormal overproduction of serum oxalate and recurrent kidney stones. Rarely, it can lead to crystal arthropathy and calcinosis cutis. Especially after long-term hemodialysis treatment, this disease can also cause severe hypercalcemia in rare cases. Herein, we present a 35-year-old female patient who was admitted to the nephrology clinic with painful lesions on the fingertips, bilateral wrist arthritis, and severe hypercalcemia. She had endstage renal disease due to recurrent kidney stones and had been treated with hemodialysis for 9 years. Her kidney stones had never been examined. She had a history of total parathyroidectomy for tertiary hyperparathyroidism 4 years ago. A physical examination revealed painful lesions of 1 to 2 mm on the erythematous ground in the distal phalanx of the fingers and nail beds. At the same time, there was swelling, hyperemia, and joint motion restriction in the two wrists. Therefore, in another hospital, low-dose steroid therapy was started 1 month ago, considering seronegative arthritis. She had not used a calcium-based phosphorus binder and/or vitamin D3 or synthetic vitamin D analog for the past 3 months. Laboratory tests revealed serum calcium: 15.7 (normal: 8.5–10.5) mg/dL, serum phosphorus: 3.5 (normal: 2.3–4.7) mg/dL, parathormone: 0.3 (normal: 18–88) pg/mL, serum alkaline phosphatase: 240 (normal: 30–120) U/L, serum albumin: 2.5 g/dL, and hemoglobin: 7.9 g/dL. The erythrocyte sedimentation rate was 61 /hours, C-reactive protein (CRP) was 5.4 mg/L, and rheumatoid factor was 3 (0–14) IU/mL. Posteroanterior (PA) chest X-ray demonstrated nodular opacities in the upper zones of both lungs (arrows) and resorption of bilateral humeral heads (arrowheads) (Figure 1A). Thoracic computed tomography (CT) showed massive sclerosis and subperiosteal resorption in both clavicles (arrowheads), first ribs (arrows), and humeral heads without any pathology in the upper zones of the lung parenchyma (Figure 1B). Bone morrow biopsy was performed due to severe hypercalcemia and erythropoiesis-stimulating agents resistance anemia. Her biopsy demonstrated crystal deposition with sequential in a radial pattern and granulomatous reactions (Figure 2A). It included double light-refracting crystals under a polarized microscope (Figure 2B) concordant with oxalate crystals. The diagnosis of primary hyperoxaluria was confirmed with a mutational analysis of the AGXT gene (Lys12GlnfsX156 homozygous mutation). Invasion of the bone marrow by a granuloma in response to the oxalate deposition was considered as the cause of the severe hypercalcemia. All clinical signs were associated with primary hyperoxaluria. Six-hour-long hemodialysis with low calcium dialysate (1.25 mmol/L) was performed six times per week to remove the oxalate and treating the hypercalcemia. After the 2nd week, the patient’s pain subsided. Serum calcium levels decreased to reasonable levels (serum calcium: 9.5 mg/dL). Frequent and longer hemodialysis treatment was planned until transplantation. The patient was referred to the transplantation center for both liver and kidney transplantation. As a result, primary hyperoxaluria may be fatal by causing accumulation of oxalate in all organs, especially bones and kidneys. It should be considered in the differential diagnosis of arthritis and calcinosis cutis. Correspondence to: E. Tatar, MD, Division of Nephrology, University of Health Sciences, Izmir Bozyaka Education and Research Hospital, +9035170, Karabaglar, Izmir, Turkey. E-mail: [email protected] Conflict of Interest: The authors declared no conflicts of interest with respect to the authorship and/or publication of this article. Disclosure: Informed consent was obtained from patient included in the case report.