Detection of measles virus nucleocapsid transcripts in circulating blood cells from patients with Paget disease

Paget disease of bone is characterized by abnormalities in all phases of bone remodeling, but the fundamental cellular abnormality resides in the osteoclast (OCL). Osteoclasts in bone involved by Paget disease contain viral-like nuclear and cytoplasmic inclusions that react with antibodies directed against paramyxovirus nucleocapsid proteins, such as measles virus, respiratory syncytial virus, or canine distemper virus. However, the identity of the virus or the mechanisms responsible for its persistence or pathologic role in Paget disease is unclear. Furthermore, although Paget disease persists for many years, it remains a highly localized process with new lesions rarely if ever developing in previously unaffected bones. Since osteoclasts are formed by fusion of mononuclear precursors derived from colony forming unit-granulocyte macrophage (CFU-GM), the granulocyte-macrophage progenitor, we used reverse transcriptase polymerase chain reaction (RT-PCR) analysis to determine if CFU-GM, more differentiated osteoclast precursors, and peripheral blood cells derived from CFU-GM express measles virus nucleocapsid (MV-N) transcripts. We found that osteoclast precursors, as well as peripheral blood mononuclear cells, express MV transcripts in 9 of 13 patients. Sequence analysis of the PCR amplified products confirmed nucleotide identity of MV-N transcripts expressed in peripheral blood and bone marrow-derived cells from the same patient. In contrast, MV-N transcripts were not detected in OCL precursors or the peripheral blood from 10 normal subjects. In situ hybridization studies using 35S-labeled antisense riboprobes to MV-N transcripts further confirmed the expression of MV transcripts in these cells. Sequence analysis of the PCR amplified product from one of these patients also identified a novel mutation that converted lysine441 to glutamic acid441 in the MV-N transcript. These data demonstrate that OCL precursors and circulating peripheral blood cells also express MV transcripts in patients with Paget disease and suggest that the pagetic marrow microenvironment plays a critical role in maintaining the highly localized nature of the lesions in Paget disease.

Abnormal systemic metabolism of iron, porphyrin, and calcium in Fahr's syndrome

Striopallidodentate calcinosis (Fahr's disease) is characterized clinically by seizures, rigidity, and dementia and pathologically by mineral deposition in the basal ganglia, dentate nucleus, and cerebral cortex. Disorders of iron and calcium-phosphate metabolism are thought to play a role in its pathogenesis. We present the case of a patient with familial striopallidodentate calcinosis who had porphyria cutanea tarda, refractory anemia, and pseudohypoparathyroidism type 2. The serum level of ferritin was markedly increased, serum iron and iron-binding capacity were below normal, and at autopsy she had deposition of iron in liver, spleen, bone marrow, and brain. She showed intermittent mild hypocalcemia, increased serum values of parathyroid hormone, elevated renal tubular reabsorption of phosphate, and low serum levels of 1,25-dihydroxyvitamin D, suggesting blunted renal responsiveness to endogenous parathyroid hormone. Pseudohypoparathyroidism type 2 was confirmed by infusion of synthetic parathyroid hormone, which gave a normal urinary cyclic adenosine monophosphate response, but a blunted phosphaturic response. After splenectomy for hypersplenism and weekly phlebotomies, she showed progressive improvement in function, mental status, weight, and seizure control. The hypothesis advanced is that the underlying pathophysiology of the separate diseases contributed to the formation of the brain stones through mechanisms of defective iron transport and free radical production.