Persistent phosphaturic mesenchymal tumor causing tumor-induced osteomalacia treated with image-guided ablation

Phosphaturic mesenchymal tumors (PMTs) can present with vague symptoms of diffuse bone pain with pathologic fractures that often lead to a delayed diagnosis. We present a 60-year-old patient with a PMT that was persistently hypophosphatemic after resection, who was then successfully treated with cryoablation of the tumor. Tumor-induced osteomalacia (TIO) is a rare cause of hypophosphatemia characterized by vague symptoms of gradual muscle weakness and diffuse bone pain with pathologic fractures that often lead to a delayed diagnosis. This condition is usually caused by benign phosphaturic mesenchymal tumors (PMTs). Here, we present a case of persistent PMT after surgical resection treated with image-guided ablation. We present the patient's clinical examinations and laboratory findings (phosphorus, 1,25 (OH)₂D, FGF-23, Intact PTH). Representative histologic images of a PMT are also presented. A 61-year-old male was evaluated for persistent hypophosphatemia and presumed osteomalacia. Six years earlier, he underwent surgical excision of a left ischial mass after presenting with TIO. The pathology was consistent with a PMT; however, hypophosphatemia persisted suggesting incomplete resection. He was treated with calcitriol and phosphate salts. A PET Ga68 dotatate scan of the patient revealed an avid left ischial mixed lytic and sclerotic lesions with marked amount of radiotracer uptake, suggesting persistent tumor. The patient was resistant to re-excision of the tumor due to the extended recovery period from his prior surgery and was treated instead with cryoablation of the tumor. His biochemical findings of hypophosphatemia and elevated FGF23 resolved after the ablation and have remained normal for 5 months after surgery. In patients with TIO, wide surgical excision is the treatment of choice. When this is not possible, image-guided ablation is an alternative therapeutic option.

A protein dissection study demonstrates that two specific hydrophobic clusters play a key role in stabilizing the core structure of the molten globule state of human alpha-lactalbumin

The molten globule state of alpha-lactalbumin (alpha LA) has served as a paradigm for understanding the role of these partially folded states in protein folding. We previously showed that a peptide construct consisting of the A and B helices (residues 1-38) cross-linked to the D- and C-terminal 3(10) helices (residues 101-120) of alpha LA is capable of folding to a stable molten globule-like state. Here, we report the study of three peptide constructs that are designed to investigate the contribution two short hydrophobic sequences located near the C-terminus of alpha LA make to the structure and stability of the alpha LA molten globule state. These regions of the protein have been shown to form stable non-native structures in isolation. The three peptide constructs contain residues 1-38 cross-linked to three separate C-terminal peptides via the native 28-111 disulfide bond. The C-terminal peptides consist of residues 101-114, 106-120, and 106-114. The results of CD, fluorescence, ANS binding, and urea denaturation experiments indicate that constructs that lack either of the hydrophobic sequences (residues 101-105 and 115-120) are significantly less structured. These results highlight the importance of long-range, mutually stabilizing interactions within the molten globule state of the protein. Proteins 2001;42:237-242.