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Extensive Metastatic Vascular Calcification in a Patient with Chronic Renal Failure and Tubercular Osteomyelitis as Seen on F-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography
Address for correspondence: Dr. Nishikant Avinash Damle, Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi - 110 029, India. E-mail: nkantdamle@gmail.com
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Abstract
A 48-year-old male with known tubercular osteomyelitis of the left elbow and chronic renal failure presented with PTH independent hypercalcemia and underwent F-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) to look for any underlying malignancy that might be causing his hypercalcemia. The PET/CT did not reveal any malignancy, but extensive metastatic calcification of small- and medium-sized arteries was noted throughout the body with relative sparing of large vessels. Alkaline tissue such as lungs, gastric mucosa, and kidneys that are usually involved in metastatic calcification were also spared. The underlying pathology for this kind of metastatic calcification was most likely chronic granulomatous disease, which was tubercular osteomyelitis in this patient. We present the PET/CT scan images of this unusual case of metastatic vascular calcification.
Keywords
Chronic renal failure
F-18 fluorodeoxyglucose positron emission tomography/computed tomography
metastatic calcification
TB osteomyelitis
vascular calcification
![Metastatic calcification can be associated with diseases such as hyperparathyroidism, Vitamin D intoxication, milk-alkali syndrome, chronic granulomatous diseases, neoplasms, and other conditions that lead to the derangement in calcium metabolism and deposition of calcium and phosphorous salts in otherwise normal tissues.[1] Here, we present the images of an F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scan done in a 48-year-old male with known tubercular osteomyelitis affecting the elbow with PTH-independent hypercalcemia to look for any malignancy. The patient was also suffering from chronic renal failure but had normal parathormone (PTH) levels of 11.5 ng/ml. The scan revealed multiple metabolically active lymph nodes involving cervical, axillary, mediastinal, retroperitoneal, and pelvic regions with calcification and necrosis suggestive of tubercular pathology. The patient was a known case of tubercular osteomyelitis, and metabolically active disease was noted involving his left elbow joint. The PET/CT did not reveal any definite evidence of malignancy, but incidentally, diffuse metastatic calcifications were noted extensively in small- and medium-sized arteries throughout the body. Figure 1a and b show metastatic calcification involving the medium and small arteries of the abdominal viscera (hepatic artery, celiac trunk, and splenic artery pointed by black arrows) and renal arteries on CT and PET/CT, respectively. Figure 1c and d show metastatic calcification of bilateral femoral arteries (white arrowhead) and multiple branches of the internal iliac arteries supplying the pelvis and perineum on CT and PET/CT, respectively. Noncontrast computed tomography maximum intensity projection images showed metastatic calcification of small- and medium-sized vessels of the abdomen [Figure 1e] and upper and lower limbs [Figure 1f]. FDG-avid coarse calcifications were seen in the shoulder and hip joints as well as the gluteal region. Figure 1c and d show soft tissue (muscle as well as subcutaneous soft tissue) calcification in the bilateral gluteal regions (solid white arrows) on CT [Figure 1c], showing increased FDG uptake on PET/CT [Figure 1d]. Furthermore, both kidneys appeared small and contracted (left > right) [stars in Figure 1a and b]. The patient's chronic kidney disease could have been a differential for the cause of the extensive vascular metastatic calcification, but normal PTH levels indicated otherwise. Moreover, relative sparing of the large arteries, which are usually involved in metastatic calcification due to chronic kidney disease[2] was noted. This was suggestive of a different pathogenesis for metastatic calcification secondary to chronic kidney disease, such as a lack of inhibitors of vascular calcification[3] or a different cause altogether, such as tubercular osteomyelitis. In chronic granulomatous diseases such as sarcoidosis, tuberculosis, and granulomatous infections, unregulated conversion of 25 (OH) Vitamin D into 1,25 (OH)2 Vitamin D (calcitriol) leads to hypercalcemia and therefore, metastatic calcification.[2] Another unusual finding in this patient was the absence of calcification in alkaline tissues such as lungs, kidneys, gastric mucosa, and basal ganglia (Figure) where metastatic calcification is commonly seen.[4] Metastatic calcification can be detected using a CT scan or Technetium-99 m labeled bone scintigraphy.[56] Appropriate differentials for soft-tissue calcifications can be approached by the distribution patterns, additional laboratory testing and clinical findings.](/content/210/2023/38/1/img/IJNM-38-74-g001.png)
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Conflicts of interest
There are no conflicts of interest.
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