Familial tumoral calcinosis: from characterization of a rare phenotype to the pathogenesis of ectopic calcification

Combined Gout and Pseudogout Demonstrate Unique Clinicopathologic Features Compared to Those With Only Gout

Although monosodium urate and calcium pyrophosphate dihydrate (CPPD) crystals have been documented together in synovial fluid, there are no descriptions regarding their simultaneous histologic presence within the same tophi. Furthermore, the incidence, significance, and clinicopathologic features of such patients have not been analyzed. We retrospectively reviewed consecutive cases of pathologic specimens over an ~4-year period with a confirmed histologic diagnosis of "gout" or "gouty tophi", focusing on concomitantly documented CPPD. A total of 159 gout cases involved 156 patients, including 127 males and 29 females (ratio 4.4:1), with ages ranging from 14 to 99 years (median 67). Nine (5.7%) patients (6 males; 3 females; ratio 2:1; age range 49 to 91 years, median 74) had evidence of both gout and CPPD crystals within the same tophaceous deposits. Concomitant gout/CPPD were more commonly associated with the upper extremities (5 [3, hands; 2, elbows]) than lower extremities (4, feet). Seven patients had a prior history of gout and 1 CPPD. The 150 cases from 147 patients of gout alone occurred in 121 males and 26 females (ratio 4.7:1), with ages ranging from 14 to 99 years (median 67). Gout alone was far more common in the lower extremities (109 cases) than the upper extremities (41). For combined gout/pseudogout, deposits of CPPD were intimately associated with the gouty tophi, deposited in irregular, curvilinear to serpiginous aggregates onto a significantly higher volume of uric acid crystals but never observed away from the tophaceous deposits. Confirmation of the uric acid crystals required polarization of unstained sections. In conclusion, the presence of concomitant CPPD and gouty crystals in the same tophaceous deposits is infrequently observed in pathology specimens. Compared with gout only, preliminary data suggests that patients with combined gout/pseudogout tophi are more likely to be older, female, and exhibit upper extremity involvement. Most such patients also have a prior history of gout.

Establishment and Molecular Characterization of a Human Stem Cell Line from a Primary Cell Culture Obtained from an Ectopic Calcified Lesion of a Tumoral Calcinosis Patient Carrying a Novel GALNT3 Mutation

BACKGROUND/OBJECTIVES

Tumoral calcinosis (TC) is an extremely rare inherited disease characterized by multilobulated, dense ectopic calcified masses, usually in the periarticular soft tissue regions. In a previous study, we isolated a primary cell line from an ectopic lesion of a TC patient carrying a previously undescribed GALNT3 mutation. Here, we researched whether a stem cell (SC) subpopulation, which may play a critical role in TC progression, could be present within these lesions.

METHODS

A putative SC subpopulation was initially isolated by the sphere assay (marked as TC1-SC line) and characterized for its stem-like phenotype through several cellular and molecular assays, including colony forming unit assay, immunofluorescence staining for mesenchymal SC (MSC) markers, gene expression analyses for embryonic SC (ESC) marker genes, and multidifferentiation capacity. In addition, a preliminary expression pattern of osteogenesis-related pathways miRNAs and genes were assessed in the TC1-SC by quantitative Real-Time PCR (qPCR).

RESULTS

These cells were capable of differentiating into both the adipogenic and the osteogenic lineages. Moreover, they showed the presence of the MSC and ESC markers, confirmed respectively by using immunofluorescence and qualitative reverse transcriptase PCR (RT-PCR), and a good rate of clonogenic capacity. Finally, qPCR data revealed a signature of miRNAs (i.e., miR-21, miR-23a-3p, miR-26a, miR-27a-3p, miR-27b-3p, and miR-29b-3p) and osteogenic marker genes (i.e., ALP, RUNX2, COLIA1, OPG, OCN, and CCN2) characteristic for the established TC1-SC line.

CONCLUSIONS

The establishment of this in vitro cell model system could advance the understanding of mechanisms underlying TC pathogenesis, thereby paving the way for the discovery of new diagnostic and novel gene-targeted therapeutic approaches for TC.

Familial tumoral calcinosis: a rare autosomal recessive disease

Familial tumoral calcinosis (FTC) is a rare autosomal recessive disorder where renal tubular phosphate excretion is decreased in the absence of renal failure. The underlying defect is due to inactivating mutations in the fibroblast growth factor 23, α-Klotho or UDP-N-acetyl-alpha-D-galactosamine: polypeptide N-acetylgalactosaminyl transferase-3 genes, resulting in hyperphosphatemia. Patients typically present with calcified soft tissue masses resulting from calcium phosphate deposits. Medical management with phosphate binders, a carbonic anhydrase inhibitor, in addition to limiting phosphorus intake, is the mainstay of treatment. This case serves to highlight the pathophysiology of a rare diagnosis of FTC and the efficacy of the limited therapeutic options available.

Familial hyperphosphatemic tumoral calcinosis: A rare case report from Syria

Key Clinical Message

Tumoral calcinosis is a very rare disease mainly caused by a disturbance in phosphate metabolism. It is advisable to contemplate screening more organs such as testes, thyroid, and spleen in patients with TC. This study provides insight into tumoral calcinosis for physicians in the region and encourages future work on the matter.

Abstract

Familial hyperphosphatemic tumoral calcinosis (FHTC) characterized by progressive deposition of calcium phosphate crystals in soft tissues. Tumoral calcinosis (TC) is often underdiagnosed in Syria as it cannot be confirmed without genetic testing, which is unavailable in Syria. We present the first reported case from Syria of a man with TC. This case has findings that were not reported in other cases such as testicular calcification, brain calcification, enlarged thyroid, and splenomegaly. Determining these genes in the case presented wasn't possible and future studies need to overcome this hurdle.

A Sole Case of the FGF23 Gene Mutation c.202A>G (p.Thr68Ala) Associated with Multiple Severe Vascular Aneurysms and a Hyperphosphatemic Variant of Tumoral Calcinosis-A Case Report

Tumoral calcinosis is an extremely rare genetic disease caused by mutations in three genes, GALNT3, FGF23, and KL, which disrupt phosphorus metabolism. The hallmark of this condition is the formation of tumors in the soft tissues around the joints. Other phenotypic features of tumoral calcinosis are dental involvement and brain and vascular calcifications. The clinical case reported herein presents for the first time to the scientific community the c.202A>G (p.Thr68Ala) mutation of the FGF23 gene, associated with a hyperphosphatemic variant of tumoral calcinosis and multiple severe vascular aneurysms. A female patient underwent multiple surgeries for tumor formations in her soft tissues that first appeared at the age of 12 months. On this occurrence, the patient was found to have hyperphosphatemia, low phosphate clearance, increased tubular reabsorption with normal levels of total and ionized calcium, vitamin D3, and parathyroid hormone, and no effect of treatment with sevelamer hydrochloride and a low-phosphate diet. At the age of 39, the patient underwent imaging studies due to edema and a pulsating formation in the neck area, which revealed multiple vascular aneurysms with thrombosis, for which she received operative and interventional treatment. In this connection, and because of the established phosphorus metabolism disturbance, a genetic disease was suspected. The sequence analysis and deletion/duplication testing of the 358 genes performed on this occasion revealed that the woman was homozygous for a variant of the c.202A>G (p.Thr68Ala) mutation of the FGF23 gene. The established mutation is not present in population databases. The presented clinical case is the first and only one in the world to demonstrate the role of this type of FGF23 gene mutation in the development of a hyperphosphatemic variant of tumoral calcinosis characterized by aggressive formation of multiple vascular aneurysms.

Recurrent Bilateral Lower Motor Neuron Type of Facial Palsy with Hearing Impairment: Hyperphosphatemic Familial Tumoral Calcinosis

Hyperphosphatemic familial tumoral calcinosis (HFTC) presents with varied neurological manifestations that have been reported in the literature like facial palsy, vision and hearing impairment, stroke, and headache. In this article, we reported a 12-year-old girl child patient with recurrent facial weakness with bilateral hearing impairment and multiple ulcerative lesions on lower limbs and elbows. On examination, she had lower motor neuron (LMN) facial palsy with conductive hearing loss. The investigations showed hyperphosphatemia (9.3 mg/dL) with normal serum calcium (10.4 mg/dL), alkaline phosphatase (147.9 U/L), parathyroid hormone (23.12 pg/mL), and renal function tests. Elevated serum calcium and phosphorus product (96.72 mg 2 /mL 2 ) and elevated renal tubular reabsorption of phosphate (TMPxGFR) value (9.16) were noted. Skeletal survey showed hyperostosis in the long bone diaphysis, vertebrae, ribs, pelvic bone, skull, and facial bones with narrowing of cranial ostium, characteristically without any peri-articular soft tissue calcifications. An angiogram showed multiple intravascular calcifications. She was managed with a low-phosphate diet, sevelamer, niacinamide, acetazolamide, sucroferric oxyhydroxide to lower serum phosphate level, and topical sodium thiosulfate ectopic cutaneous calcification. Exome sequencing showed novel homozygous inframe deletion of ACG in FGF23 gene exon 3 at c.374_376 delins position (p. Asp125del) in the proband and a mutation in the heterozygous state in the mother and elder sibling, thus confirming a molecular diagnosis of HFTC. Our case had a unique neurological presentation of recurrent bilateral lower motor nerve facial palsy, hearing loss, multiple ectopic cutaneous calcifications without peri-articular deposits, multiple intravascular, intracranial, and vertebral endplate calcification, which has not been reported earlier. The proband showed a novel pathogenic variant suggesting an expanding phenotype of HFTC.

Zebrafish Models to Study Ectopic Calcification and Calcium-Associated Pathologies

Ectopic calcification refers to the pathological accumulation of calcium ions in soft tissues and is often the result of a dysregulated action or disrupted function of proteins involved in extracellular matrix mineralization. While the mouse has traditionally been the go-to model organism for the study of pathologies associated with abnormal calcium deposition, many mouse mutants often have exacerbated phenotypes and die prematurely, limiting the understanding of the disease and the development of effective therapies. Since the mechanisms underlying ectopic calcification share some analogy with those of bone formation, the zebrafish (Danio rerio)-a well-established model for studying osteogenesis and mineralogenesis-has recently gained momentum as a model to study ectopic calcification disorders. In this review, we outline the mechanisms of ectopic mineralization in zebrafish, provide insights into zebrafish mutants that share phenotypic similarities with human pathological mineralization disorders, list the compounds capable of rescuing mutant phenotypes, and describe current methods to induce and characterize ectopic calcification in zebrafish.

A Rare Case of Bilateral Hip Tumoral Calcinosis With Intertrochanteric Fracture Treated by Closed Reduction Internal Fixation (CRIF) Using a Proximal Femoral Nail

Tumoral calcinosis, also referred to as Teutschländer disease is a rare familial disorder characterized by painless, periarticular lumps or masses. Large amorphous calcific concentrations that surround the joints are the defining feature. These lesions have fibrous septa that divide them into lobules and may often show fluid/calcium levels (milk of calcium/suspended hydroxyapatite crystals). In our case report, a 24-year-old male came to the outpatient department (OPD) with complaints of pain over the right hip for two days and swelling over both hips for six years. He was apparently well two days prior to the hospital visit, when he met with a road traffic accident, falling off his bike. A plain radiograph of the pelvis and bilateral hip joints along with cross-table lateral views were done, which depicted a typical appearance of amorphous and multilobulated ("cloud-like") calcifications located in a periarticular distribution in both hips along with an intertrochanteric fracture in the right hip. A CT scan, done for better delineation of the calcific masses and fracture pattern, showed no obvious erosion or osseous destruction by the adjacent soft-tissue masses. Laboratory investigations revealed a serum calcium level of 8.8 mg/dl and a serum phosphorous level of 6.0 mg/dl.  The patient was taken up for surgery after routine pre-operative investigations and a pre-anaesthesia check-up. Closed reduction internal fixation (CRIF) was done using a proximal femoral nail (PFN). A biopsy of the soft-tissue masses was sent for histopathology, which was suggestive of lobules of calcific material surrounded by histiocytic giant cells. The patient responded well to the treatment with no residual discharge from the incision site, and his treatment was continued with phosphate binders as prescribed by the endocrinologist.

A novel FGF23 mutation in hyperphosphatemic familial tumoral calcinosis and its deleterious effect on protein O-glycosylation

BACKGROUND

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare disease characterized by hyperphosphatemia and ectopic calcification, predominantly at periarticular locations. This study was performed to characterize the clinical profile of tumoral calcinosis and to identify gene mutations associated with HFTC and elucidated its pathogenic role.

METHODS

The three subjects (two male and one female) were aged 30, 25 and 15 years, respectively. The clinical features, histopathological findings, and outcomes of three subjects with HFTC were retrospectively reviewed. The three subjects were analyzed for FGF23, GALNT3 and KL mutations. Function of mutant gene was analyzed by western blotting and wheat germ agglutinin affinity chromatography.

RESULTS

All subjects had hyperphosphatemia and elevated calcium-phosphorus product. Calcinosis positions included the left shoulder, left index finger, and right hip. Bone and joint damage were present in two cases and multiple foci influenced body growth in one case. The histopathological features were firm, rubbery masses comprising multiple nodules of calcified material bordered by the proliferation of mononuclear or multinuclear macrophages, osteoclastic-like giant cells, fibroblasts, and chronic inflammatory cells. The novel mutation c.484A>G (p.N162D) in exon 3 of FGF23 was identified in one subject and his family members. Measurement of circulating FGF23 in the subject confirmed low intact FGF23 and increased C-terminal fragment. In vitro experiments showed that the mutant FGF23 proteins had defective O-glycosylation and impaired protein proteolysis protection.

CONCLUSION

We identified a novel FGF23 missense mutation, and confirmed its damaging role in FGF23 protein O-glycosylation. Our findings expand the current spectrum of FGF23 variations that influence phosphorus metabolism.

Role of Glycosylation in Vascular Calcification

Glycosylation is an important step in post-translational protein modification. Altered glycosylation results in an abnormality that causes diseases such as malignancy and cardiovascular diseases. Recent emerging evidence highlights the importance of glycosylation in vascular calcification. Two major types of glycosylation, N-glycosylation and O-glycosylation, are involved in vascular calcification. Other glycosylation mechanisms, which polymerize the glycosaminoglycan (GAG) chain onto protein, resulting in proteoglycan (PG), also have an impact on vascular calcification. This paper discusses the role of glycosylation in vascular calcification.

Bone Involvement in Hyperphosphatemic Familial Tumoral Calcinosis: A New Phenotypic Presentation

Mutations in FGF23, KL, and GALNT3 have been identified as the cause for the development of hyperphosphatemic familial tumoral calcinosis (HFTC). Patients with HFTC typically present in childhood or adolescence with periarticular soft tissue deposits that eventually progress to disrupt normal joint articulation. Mutations in the GALNT3 gene were shown to account for the hyperphosphatemic state in both HFTC and hyperostosis-hyperphosphatemia syndrome (HHS), the latter characterized by bone involvement. We present the case of a patient of a Druze ethnic origin with known HFTC that presented to our department with the first documented case of pathologic fracture occurring secondary to the disease. Our report introduces this new phenotypic presentation, suggests a potential role for prophylactic bone screening, and highlights the need for preconception genetic screening in selected populations.

Recurrence of tumoral calcinosis: a case report

We describe radiographic, contrast-enhanced MDCT and MRI findings with pathologic correlations of an unusual recurrence of tumoral calcinosis, also called Teutschlander disease. The disease was silent in the first decade of life, when it appeared with elbows recurring lesions, until the seventh decade of life, when a left hip active growth lesion developed. A review about tumoral calcinosis pathogenesis, clinical course and imaging differential diagnosis is reported. (www.actabiomedica.it).

Effects of parathyroidectomy on tumoral calcinosis in uremic patients with secondary hyperparathyroidism

BACKGROUND

Tumoral calcinosis (TC) is a rare disease derived from uremic secondary hyperparathyroidism (SHPT). However, parathyroidectomy (PTX) seems to be ineffective at relieving TC in some patients. In this study, we investigated the relationship between PTX and TC shrinkage.

METHODS

We retrospectively followed up nine TC patients who underwent PTX, dividing them into two groups: those with TC size reduced by > 80% were in the "effective group" (group A), and the rest in the "ineffective group" (group B).

RESULTS

We enrolled nine patients (7 men; mean age 38.6 ± 10.9 years) with SHPT-related TC. One patient with calciphylaxis was excluded due to sudden death. The efficiency of PTX in causing TC regression was 62.5% (5 patients in group A). Group A had a shorter overall duration of TC (6 [5.5, 6.0] vs. 9 [8.0, 10.0] months; P = 0.02) and higher serum levels of alkaline phosphatase (ALP; 408.0 [217.9, 1101.7] vs. 90.8 [71.0, 102.1] pg/ml; P = 0.03) and high-sensitivity C-reactive protein (hs-CRP; 82.7 [55.0, 112.4] vs. 3.1 [3.1, 4.5] mg/l; P = 0.02). Average calcium supplementation within 1 week of surgery was significantly greater in group A than in group B (96.8 [64.1, 105.3] vs. 20.1 [13.1, 32.7] g; P = 0.04). Patients in both the groups demonstrated similar serum phosphate levels before PTX, but these levels were higher in group B than in group A at follow-up times (3 months, P = 0.03; 6 months, P = 0.03).

CONCLUSIONS

The shorter duration of pre-existing TC and higher ALP levels before PTX, as well as lower serum phosphate levels after PTX, were correlated with effective SHPT-TC shrinkage.

Disorders of phosphate metabolism

Phosphate in both inorganic and organic form is essential for several functions in the body. Plasma phosphate level is maintained by a complex interaction between intestinal absorption, renal tubular reabsorption, and the transcellular movement of phosphate between intracellular fluid and bone storage pools. This homeostasis is regulated by several hormones, principally the parathyroid hormone, 1,25-dihydroxyvitamin D and fibroblast growth factor 23. Abnormalities in phosphate regulation can lead to serious and fatal complications. In this review phosphate homeostasis and the aetiology, pathophysiology, clinical features, investigation and management of hypophosphataemia and hyperphosphataemia will be discussed.

Quantitative Trait Locus and Integrative Genomics Revealed Candidate Modifier Genes for Ectopic Mineralization in Mouse Models of Pseudoxanthoma Elasticum

Pseudoxanthoma elasticum, a prototype of heritable multisystem ectopic mineralization disorders, is caused by mutations in the ABCC6 gene encoding a putative efflux transporter, ABCC6. The phenotypic spectrum of pseudoxanthoma elasticum varies, and the correlation between genotype and phenotype has not been established. To identify genetic modifiers, we performed quantitative trait locus analysis in inbred mouse strains that carry the same hypomorphic allele in Abcc6 yet with highly variable ectopic mineralization phenotypes of pseudoxanthoma elasticum. Abcc6 was confirmed as a major determinant for ectopic mineralization in multiple tissues. Integrative analysis using functional genomics tools that included GeneWeaver, String, and Mouse Genome Informatics identified a total of nine additional candidate modifier genes that could influence the organ-specific ectopic mineralization phenotypes. Integration of the candidate genes into the existing ectopic mineralization gene network expands the current knowledge on the complexity of the network that, as a whole, governs ectopic mineralization in soft connective tissues.

Pseudoxanthoma Elasticum as a Paradigm of Heritable Ectopic Mineralization Disorders: Pathomechanisms and Treatment Development

Ectopic mineralization is a global problem and leading cause of morbidity and mortality. The pathomechanisms of ectopic mineralization are poorly understood. Recent studies on heritable ectopic mineralization disorders with defined gene defects have been helpful in elucidation of the mechanisms of ectopic mineralization in general. The prototype of such disorders is pseudoxanthoma elasticum (PXE), a late-onset, slowly progressing disorder with multisystem clinical manifestations. Other conditions include generalized arterial calcification of infancy (GACI), characterized by severe, early-onset mineralization of the cardiovascular system, often with early postnatal demise. In addition, arterial calcification due to CD73 deficiency (ACDC) occurs late in life, mostly affecting arteries in the lower extremities in elderly individuals. These three conditions, PXE, GACI, and ACDC, caused by mutations in ABCC6, ENPP1, and NT5E, respectively, are characterized by reduced levels of inorganic pyrophosphate (PPi) in plasma. Because PPi is a powerful antimineralization factor, it has been postulated that reduced PPi is a major determinant for ectopic mineralization in these conditions. These and related observations on complementary mechanisms of ectopic mineralization have resulted in development of potential treatment modalities for PXE, including administration of bisphosphonates, stable PPi analogs with antimineralization activity. It is conceivable that efficient treatments may soon become available for heritable ectopic mineralization disorders with application to common calcification disorders.

Dialysis as a Treatment Option for a Patient With Normal Kidney Function and Familial Tumoral Calcinosis Due to a Compound Heterozygous FGF23 Mutation

Primary tumoral calcinosis is a rare autosomal recessive disorder characterized by ectopic calcified tumoral masses. Mutations in 3 genes (GALNT3, FGF23, and KL) have been linked to this human disorder. We describe a case of a 28-year-old man with a history of painful firm masses over his right and left gluteal region, right clavicle region, knees, and left elbow. Biochemical analysis disclosed hyperphosphatemia (phosphate, 9.0 mg/dL) and normocalcemia (calcium, 4.8 mg/dL), with normal kidney function and fractional excretion of phosphate of 3%. Parathyroid hormone was suppressed (15 pg/mL), associated with a low-normal 25-hydroxyvitamin D (26 ng/mL) concentration but high 1,25-dihydroxyvitamin D concentration (92 pg/mL). Serum intact FGF-23 (fibroblast growth factor 23) was undetectable. Genetic analysis revealed tumoral calcinosis due to a compound heterozygous mutation in FGF23, c.201G>C (p.Gln67His) and c.466C>T (p.Gln156*). Due to lack of other treatment options and because the patient was facing severe vascular complications, we initiated a daily hemodialysis program even in the setting of normal kidney function. This unusual therapeutic option successful controlled hyperphosphatemia and reduced metastatic tumoral lesions. This is a report of a new mutation in FGF23 in which dialysis was an effective treatment option for tumoral calcinosis with normal kidney function.

Ectopic mineralization of cartilage and collagen-rich tendons and ligaments in Enpp1asj-2J mice

Generalized arterial calcification of infancy (GACI), an autosomal recessive disorder caused by mutations in the ENPP1 gene, manifests with extensive mineralization of the cardiovascular system. A spontaneous asj-2J mutant mouse has been characterized as a model for GACI. Previous studies focused on phenotypic characterization of skin and vascular tissues. This study further examined the ectopic mineralization phenotype of cartilage, collagen-rich tendons and ligaments in this mouse model. The mice were placed on either control diet or the ‘acceleration diet’ for up to 12 weeks of age. Soft connective tissues, such as ear (elastic cartilage) and trachea (hyaline cartilage), were processed for standard histology. Assessment of ectopic mineralization in articular cartilage and fibrocartilage as well as tendons and ligaments which are attached to long bones were performed using a novel cryo-histological method without decalcification. These analyses demonstrated ectopic mineralization in cartilages as well as tendons and ligaments in the homozygous asj-2J mice at 12 weeks of age, with the presence of immature osteophytes displaying alkaline phosphatase and tartrate-resistant acid phosphatase activities as early as at 6 weeks of age. Alkaline phosphatase activity was significantly increased in asj-2J mouse serum as compared to wild type mice, indicating increased bone formation rate in these mice. Together, these data highlight the key role of ENPP1 in regulating calcification of both soft and skeletal tissues.

[Vascular calcification in pseudoxanthoma elasticum in children]

INTRODUCTION

Vascular calcifications are associated with several diseases that affect vascular connective tissue and skin and cause considerable morbidity and mortality. The prototype of these conditions is pseudoxanthoma elasticum. We report, in this study, 4 pediatric cases of vascular calcifications diagnosed as elastic pseudoxanthoma.

OBSERVATIONS

These 4 children were 2-11 years old and presented variable clinical features. Vascular involvement and arterial hypertension was observed in all patients, skin involvement in 2 cases, gastrointestinal involvement in 2 cases, neurological impairment in one case, and cardiac involvement in one case. Demonstration of ABCC6 gene mutations provided diagnostic confirmation in all cases.

CONCLUSION

Pseudoxanthoma elasticum is a rare genetic disease, which can lead to many complications. Appropriate knowledge and early diagnosis are essential.

Correlation of polypeptide N-acetylgalactosamine transferases-3 and -6 to different stages of endometriosis

PURPOSE

To investigate the expression patterns of N-acetyl galactosamine transferases (GalNAc-Ts)-3 and GalNAc-T6 in clinicopathologically characterized endometriosis (EMS), and to explore their clinical significance.

METHODS

Ectopic and eutopic endometrial tissue samples were obtained and confirmed with CD-10 immunohistochemistry in patients with EMS (n = 12), whereas normal control endometrium was obtained from patients with uterine septum (n = 12). The mRNA and protein levels of GalNAc-T3 and GalNAc-T6 were detected in these samples using quantitative real-time PCR, immunohistochemistry, and western blotting.

RESULTS

GalNAc-T3 and GalNAc-T6 were expressed in the endometrium of all groups, with no significant changes observed during the menstrual cycle. The expression of GalNAc-T3 and GalNAc-T6 in ectopic endometrium was significantly lower than that in eutopic (P < 0.05) or control endometrium (P < 0.05), whereas there were no significant differences (P > 0.05) between eutopic and control endometria. Furthermore, the expression of GalNAc-T3 and GalNAc-T6 was significantly lower in patients with stage III/IV EMS compared to patients with stage I/II (P < 0.05).

CONCLUSIONS

Both GalNAc-T3 and GalNAc-T6 expression levels were downregulated in ectopic endometrium, which may increase the adhesion and invasion of endometrial cells and contribute to the development of EMS. Moreover, we found a strong correlation between the expression of GalNAc-T3 and GalNAc-T6 and different stages of EMS.

An interaction domain in human SAMD9 is essential for myxoma virus host-range determinant M062 antagonism of host anti-viral function

In humans, deleterious mutations in the sterile α motif domain protein 9 (SAMD9) gene are associated with cancer, inflammation, weakening of the immune response, and developmental arrest. However, the biological function of SAMD9 and its sequence-structure relationships remain to be characterized. Previously, we found that an essential host range factor, M062 protein from myxoma virus (MYXV), antagonized the function of human SAMD9. In this study, we examine the interaction between M062 and human SAMD9 to identify regions that are critical to SAMD9 function. We also characterize the in vitro kinetics of the interaction. In an infection assay, exogenous expression of SAMD9 N-terminus leads to a potent inhibition of wild-type MYXV infection. We reason that this effect is due to the sequestration of viral M062 by the exogenously expressed N-terminal SAMD9 region. Our studies reveal the first molecular insight into viral M062-dependent mechanisms that suppress human SAMD9-associated antiviral function.

FGF23-S129F mutant bypasses ER/Golgi to the circulation of hyperphosphatemic familial tumoral calcinosis patients

FGF23 is essential for the homeostasis of phosphate, and vitamin D. Loss-of-function mutations in this hormone cause hyperphosphatemic familial tumoral calcinosis (HFTC). Earlier reports suggested that intact FGF23 from loss of function mutants such as FGF23/S129F (iFGF23/S129F) is retained intracellularly while the carboxy-terminal fragment is secreted. We sought to investigate the fate of iFGF23/S129F mutant hormone in vivo and in vitro. Five patients clinically diagnosed with HFTC and confirmed by DNA sequencing to carry the c.386 C>T; p.S129F mutation in the homozygous state were studied. Healthy and heterozygous individuals were used as controls in the study. Using ELISA assays, we showed that iFGF23/S129F was 2-5 folds higher in patients' plasma, compared to heterozygous or healthy controls. Importantly, the mutant hormone could not be detected in the patients' sera. However, using proteinase inhibition profiling, we found that a serum metalloproteinase degraded the iFGF23/S129F explaining our failure to detect it in sera. The serum metalloproteinase degrades the WT and the mutant at different rates. Also, confocal microscopy imaging using wild-type (WT) FGF23 or FGF23/S129F mutant in transiently transfected HEK293 and HeLa cells showed weak staining of the Golgi complex with some vesicular staining resembling the ER. Additionally, FGF23 variants (FGF23/WT, FGF23/S129F, FGF23/S71G, and FGF23/R176Q) from stably transfected HEK293 cells secreted high levels into a serum-free medium that can be detected by ELISA and Western blot. Our results suggest that iFGF23/S129F mutant bypasses the ER/Golgi quality control system to the circulation of HFTC patients by an unknown pathway. Finally, we hypothesize that either the mutant hormone is unable to bind α-Klotho-FGFR1c, or it binds the dyad receptor with low affinity and, therefore, incapable of initiating maximal intracellular signaling. Our findings raise the potential use of the WT hormone in therapies of some HFTC patients.

Identification of two novel mutations in the GALNT3 gene in a Chinese family with hyperphosphatemic familial tumoral calcinosis

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare, autosomal recessive genetic disease. This disease is characterized by the progressive calcification of soft tissues leading to symptoms of pressure and hyperphosphatemia but normal concentrations of serum calcium with or without an elevation of 1,25-dihydroxyvitamin D₃ levels.HFTC is caused by loss-of-function mutations in the GALNT3, FGF23 or KL genes. Here, we identified two novel mutations in the GALNT3 gene in a Chinese family with HFTC. Identification of a novel genotype in HFTC provides clues for understanding the phenotype-genotype relationships in HFTC and may assist not only in the clinical diagnosis of HFTC but also in the interpretation of the genetic information used for prenatal diagnosis and genetic counseling.

Tumoral Calcinosis as an Initial Complaint of Juvenile-Onset Amyopathic Dermatomyositis

Calcinosis is rarely observed in juvenile-onset amyopathic dermatomyositis in contrast to juvenile-onset dermatomyositis. A 6-year-old female presented with several 0.5 to 2 cm-sized painless grouped masses on both knees for 3 years. The patient also presented with multiple erythematous scaly patches and plaques on both elbows, knuckles, buttock, ankles and cheeks. Her mother had similar skin lesions which were erythematous scaly patches on the knuckles and elbows, since her childhood. When skin biopsy was performed from a left knee nodule, liquid chalky discharge was observed. The biopsy results were consistent with calcinosis cutis. Other biopsies from erythematous patch of the patient and erythematous patch of her mother showed vacuolization of basal cell layer with inflammatory cell infiltrations. Laboratory findings showed normal range of serum phosphorus (4.5 mg/dl), calcium (9.3 mg/dl), 1,25-dihydroxy-vitamin D (10.8 ng/ml) and parathyroid hormone levels (11 pg/ml). Both patient and her mother had no history of muscle weakness and showed normal levels of muscle-specific enzyme. Both patients were diagnosed with juvenile-onset amyopathic dermatomyositis based on histopathology and cutaneous manifestations with no evidence of muscle weakness and no serum muscle enzyme abnormalities. Tumoral calcium deposits observed in daughter was diagnosed as dystrophic calcinosis which can be rarely seen in juvenile-onset amyopathic dermatomyositis. The patient is being treated with oral acetazolamide (40 mg/kg/d) for calcinosis.

The effects of bisphosphonates on ectopic soft tissue mineralization caused by mutations in the ABCC6 gene

Pseudoxanthoma elasticum (PXE) and generalized arterial calcification of infancy (GACI) are heritable ectopic mineralization disorders. Most cases of PXE and many cases of GACI harbor mutations in the ABCC6 gene. There is no effective treatment for these disorders. We explored the potential efficacy of bisphosphonates to prevent ectopic calcification caused by ABCC6 mutations by feeding Abcc6(-/-) mice with diet containing etidronate disodium (ETD) or alendronate sodium trihydrate (AST) in quantities corresponding to 1x, 5x, or 12x of the doses used to treat osteoporosis in humans. The mice were placed on diet at 4 weeks of age, and the degree of mineralization was assessed at 12 weeks by quantitation of the calcium deposits in the dermal sheath of vibrissae, a progressive biomarker of the mineralization, by computerized morphometry of histopathologic sections and by direct chemical assay of calcium. We found that ETD, but not AST, at the 12x dosage, significantly reduced mineralization, suggesting that selected bisphosphonates may be helpful for prevention of mineral deposits in PXE and GACI caused by mutations in the ABCC6 gene, when combined with careful monitoring of efficacy and potential side-effects.

Calcium orthophosphates (CaPO4): occurrence and properties

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates (CaPO4). This type of materials is of the special significance for the human beings because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with CaPO4, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenorthophosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of CaPO4. Similarly, dental caries and osteoporosis might be considered as in vivo dissolution of CaPO4. In addition, natural CaPO4 are the major source of phosphorus, which is used to produce agricultural fertilizers, detergents and various phosphorus-containing chemicals. Thus, there is a great significance of CaPO4 for the humankind and, in this paper, an overview on the current knowledge on this subject is provided.

Tumoral calcinosis in a patient with hypoparathyroidism, sensorineural deafness, and renal dysplasia syndrome undergoing hemodialysis

We describe a hemodialysis patient with hypoparathyroidism due to HDR (hypoparathyroidism, sensorineural deafness, and renal dysplasia) syndrome caused by GATA3 mutation. She presents tumoral calcinosis which is a rare complication of end-stage renal failure. A novel mutation of GATA3 is identified in this patient.

Hyperphosphatemic familial tumoral calcinosis: odontostomatologic management and pathological features

BACKGROUND

Hyperphosphatemic familial tumoral calcinosis (HFTC) is to a rare autosomal recessive disorder characterized by cutaneous and sub-cutaneous calcified masses, usually adjacent to large joints. The aim of the current study was to report on the clinico-pathological features of a patient with HFCT, with emphasis on alterations in the jawbones and teeth and the subsequent therapeutic interventions.

CASE REPORT

A 13-year-old male patient with HFTC diagnosis came to our attention for dental anomalies and maxillary and mandibular hypoplasia. OPT highlighted multiple impacted teeth, short and bulbous teeth, and pulp chamber and canal obliterations. Lateral cephalometric radiograms pointed out retrusion of both jaws, skeletal class II malocclusion, and deep-bite. He underwent orthopedic, orthodontic, conservative, and surgical treatments, allowing the correction of maxillo-facial and dental abnormalities and dysmorphisms without adverse effects. The surgical samples were sent for conventional and confocal laser scanning microscope (CLSM) histopathological examination, which highlighted several metaplastic micro- and macro-calcifications in the soft tissues, and typical islands of homogenous, non-tubular, dentino-osteoid calcified structures in dentinal tissues.

CONCLUSIONS

The management of maxillo-facial abnormalities in patients affected by HFTC is very difficult and, requires a combined therapeutic approach. To date, very few indications have been published in the literature.

Severe vascular calcification and tumoral calcinosis in a family with hyperphosphatemia: a fibroblast growth factor 23 mutation identified by exome sequencing

BACKGROUND

Tumoral calcinosis is an autosomal recessive disorder characterized by ectopic calcification and hyperphosphatemia.

METHODS

We describe a family with tumoral calcinosis requiring amputations. The predominant metabolic anomaly identified in three affected family members was hyperphosphatemia. Biochemical and phenotypic analysis of 13 kindred members, together with exome analysis of 6 members, was performed.

RESULTS

We identified a novel Q67K mutation in fibroblast growth factor 23 (FGF23), segregating with a null (deletion) allele on the other FGF23 homologue in three affected members. Affected siblings had high circulating plasma C-terminal FGF23 levels, but undetectable intact FGF23 or N-terminal FGF23, leading to loss of FGF23 function.

CONCLUSIONS

This suggests that in human, as in experimental models, severe prolonged hyperphosphatemia may be sufficient to produce bone differentiation proteins in vascular cells, and vascular calcification severe enough to require amputation. Genetic modifiers may contribute to the phenotypic variation within and between families.

Familial tumoral calcinosis

INTRODUCTION

Tumoral calcinosis is a rare condition characterised by progressive, ectopic, periarticular deposits of calcium. These tumour-like growths often infiltrate muscle and tendon, usually presenting as multiple masses or as a painless, solitary mass. Our case report will focus on familial tumoral calcinosis, an autosomal recessive metabolic disorder generally observed in patients within the first two decades of life.

CASE PRESENTATION

Our case report introduces two Sudanese siblings from consanguineous parents who presented with simultaneous recurrent multiple soft tissue swellings.

CONCLUSION

The cases discussed highlight the main features of familial tumoral calcinosis and indicate the need for improved clinical guidance on the investigations, treatment and genetic screening of familial tumoral calcinosis.

PSEUDOXANTHOMA ELASTICUM: DIAGNOSTIC FEATURES, CLASSIFICATION, AND TREATMENT OPTIONS

INTRODUCTION

Pseudoxanthoma elasticum (PXE), a multisystem orphan disease, clinically affects the skin, the eyes, and the cardiovascular system with considerable morbidity and mortality. The clinical manifestations reflect the underlying pathology consisting of ectopic mineralization of peripheral connective tissues.

AREAS COVERED

The diagnostic criteria of PXE include characteristic clinical findings, together with histopathology of accumulation of pleiomorphic elastic structures in the dermis with progressive mineralization, and the presence of mutations in the ABCC6 gene. PXE-like cutaneous changes can also be encountered in other ectopic mineralization disorders, including generalized arterial calcification of infancy (GACI) caused by mutations in the ENPP1 gene. In some cases, overlapping clinical features of PXE/GACI, associated with mutations either in ABCC6 or ENPP1, have been noted. PXE demonstrates considerable inter- and intrafamilial heterogeneity, and consequently, accurate diagnosis is required for appropriate classification with prognostic implications. There is no effective and specific treatment for the systemic manifestations of PXE, but effective therapies to counteract the ocular complications are in current clinical use.

EXPERT OPINION

A number of observations in the murine model, the Abcc6^-/- mouse, have indicated that the mineral composition of diet, particularly the magnesium content, can influence the severity of the mineralization phenotype. These observations suggest that appropriate dietary interventions, coupled with lifestyle modifications, including smoking cessation, might alleviate the symptoms and improve the quality of life of individuals affected with this, currently intractable, orphan disease.

Hyperphosphatemic familial tumoral calcinosis: response to acetazolamide and postulated mechanisms

Hyperphosphatemic familial tumoral calcinosis (HFTC) is characterized by enhanced renal phosphate absorption, hyperphosphatemia, and tumor-like extraosseous calcifications due to inactivating mutations in FGF23 or associated proteins. Surgical excision is needed when low phosphate diet and phosphate binders are ineffective. Sporadic reports have supported acetazolamide use. We report on a 7-year-old African American boy who presented with severe HFTC requiring numerous surgical excisions. Tumors continued to appear and others reoccurred despite phosphate restriction and sevelamer carbonate. At the age of 9.5 years, acetazolamide (40 mg/kg/day) was added and resulted in mild metabolic acidosis (bicarbonate 25.3 mEq/L vs. 21.4 mEq/L, P < 0.001; serum pH 7.38 vs. 7.31, P = 0.013, pre- and post-acetazolamide, respectively) but no change in tubular reabsorption of phosphate (TRP) (96.9% vs. 95.9%, P = 0.34) or serum phosphate (6.6 mg/dl vs. 6.9 mg/dl, P = 0.52 pre- and post-acetazolamide, respectively). Following the initiation of acetazolamide therapy, the patient experienced significant improvement in disease course as indicated by resolution of localized bone pain, cessation of tumor formation, and no tumor recurrence. Despite mild metabolic acidosis, our patient had improved linear growth and did not develop any other side effects related to therapy. Intact FGF23 remained abnormally low throughout disease course, while C-terminal FGF23 increased with acetazolamide. We conclude that acetazolamide can control severe HFTC by inducing mild metabolic acidosis despite no change in serum phosphate or TRP. This effect may be exerted though improved calcium-phosphate complex solubility and increased FGF23 locally.

Mutations in the ABCC6 gene as a cause of generalized arterial calcification of infancy: genotypic overlap with pseudoxanthoma elasticum

Generalized arterial calcification of infancy (GACI) is an autosomal recessive disorder characterized by congenital calcification of large- and medium-sized arteries, associated with early myocardial infarction, heart failure, and stroke, and premature death. Most cases of GACI are caused by mutations in the ENPP1 gene. We first studied two siblings with GACI from a non-consanguineous family without mutations in the ENPP1 gene. To search for disease-causing mutations, we identified genomic regions shared between the two affected siblings but not their unaffected parents or brother. The ABCC6 gene, which is mutated in pseudoxanthoma elasticum (PXE), resided within a small region of homozygosity shared by the affected siblings. Sequence analysis of ABCC6 revealed that the two affected siblings were homozygous for the missense mutation p.R1314W. Subsequently, ABCC6 mutations were identified in five additional GACI families with normal ENPP1 sequences. Genetic mutations in ABCC6 in patients with PXE are associated with ectopic tissue mineralization in the skin and arterial blood vessels. Thus, our findings provide additional evidence that the ABCC6 gene product inhibits calcification under physiologic conditions and confirm a second locus for GACI. In addition, our study emphasizes the potential utility of shared homozygosity mapping to identify genetic causes of inherited disorders.

Ectopic mineralization disorders of the extracellular matrix of connective tissue: molecular genetics and pathomechanisms of aberrant calcification

Ectopic mineralization of connective tissues is a complex process leading to deposition of calcium phosphate complexes in the extracellular matrix, particularly affecting the skin and the arterial blood vessels and common in age-associated disorders. A number of initiating and contributing metabolic and environmental factors are linked to aberrant mineralization in these diseases, making the identification of precise pathomechanistic pathways exceedingly difficult. However, there has been significant recent progress in understanding the ectopic mineralization processes through study of heritable single-gene disorders, which have allowed identification of discrete pathways and contributing factors leading to aberrant connective tissue mineralization. These studies have provided support for the concept of an intricate mineralization/anti-mineralization network present in peripheral connective tissues, providing a perspective to development of pharmacologic approaches to limit the phenotypic consequences of ectopic mineralization. This overview summarizes the current knowledge of ectopic heritable mineralization disorders, with accompanying animal models, focusing on pseudoxanthoma elasticum and generalized arterial calcification of infancy, two autosomal recessive diseases manifesting with extensive connective tissue mineralization in the skin and the cardiovascular system.

Dietary phosphate modifies lifespan in Drosophila

Phosphate is required for many important cellular processes and having too little phosphate (hypophosphatemia) or too much (hyperphosphatemia) can cause disease and reduce lifespan in humans. Drosophila melanogaster has been a powerful tool to discover evolutionarily well-conserved nutrient-sensing pathways that are important for the lifespan extension. We have established Drosophila as a model system for studying the effects of dietary phosphate during development and adult life. When absorption of phosphate is blocked by sevelamer or cellular uptake is inhibited by phosphonoformic acid (PFA), larval development is delayed in a phosphate-dependent fashion. Conversely, restriction of phosphate absorption with sevelamer or reduced cellular uptake after treatment with PFA is able to extend the adult lifespan of otherwise normal flies. Gaining an understanding of the specific pathways and mediators that regulate cellular and organismic phosphate levels might ultimately lead to the development of improved dietary and therapeutic approaches to the treatment of human disorders of hypo- and hyperphosphatemia.

Mineralization/anti-mineralization networks in the skin and vascular connective tissues

Ectopic mineralization has been linked to several common clinical conditions with considerable morbidity and mortality. The mineralization processes, both metastatic and dystrophic, affect the skin and vascular connective tissues. There are several contributing metabolic and environmental factors that make uncovering of the precise pathomechanisms of these acquired disorders exceedingly difficult. Several relatively rare heritable disorders share phenotypic manifestations similar to those in common conditions, and, consequently, they serve as genetically controlled model systems to study the details of the mineralization process in peripheral tissues. This overview will highlight diseases with mineral deposition in the skin and vascular connective tissues, as exemplified by familial tumoral calcinosis, pseudoxanthoma elasticum, generalized arterial calcification of infancy, and arterial calcification due to CD73 deficiency. These diseases, and their corresponding mouse models, provide insight into the pathomechanisms of soft tissue mineralization and point to the existence of intricate mineralization/anti-mineralization networks in these tissues. This information is critical for understanding the pathomechanistic details of different mineralization disorders, and it has provided the perspective to develop pharmacological approaches to counteract the consequences of ectopic mineralization.

Warfarin accelerates ectopic mineralization in Abcc6(-/-) mice: clinical relevance to pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE) is a multisystem ectopic mineralization disorder caused by mutations in the ABCC6 gene. Warfarin, a commonly used anticoagulant, is associated with increased mineralization of the arterial blood vessels and cardiac valves. We hypothesized that warfarin may accelerate ectopic tissue mineralization in PXE, with clinical consequences. To test this hypothesis, we developed a model in which Abcc6(-/-) mice, which recapitulate features of PXE, were fed a diet supplemented with warfarin and vitamin K1. Warfarin action was confirmed by significantly increased serum levels of oxidized vitamin K. For mice placed on a warfarin-containing diet, quantitative chemical and morphometric analyses revealed massive accumulation of mineral deposits in a number of tissues. Mice fed a warfarin-containing diet were also shown to have abundant uncarboxylated form of matrix Gla protein, which allowed progressive tissue mineralization to ensue. To explore the clinical relevance of these findings, 1747 patients with PXE from the approximately 4000 patients in the PXE International database were surveyed about the use of warfarin. Of the 539 respondents, 2.6% reported past or present use of warfarin. Based on the prevalence of PXE (approximately 1:50,000), thousands of patients with PXE worldwide may be at risk for worsening of PXE as a result of warfarin therapy.

Genetic determinants of phosphate response in Drosophila

Phosphate is required for many important cellular processes and having too little phosphate or too much can cause disease and reduce life span in humans. However, the mechanisms underlying homeostatic control of extracellular phosphate levels and cellular effects of phosphate are poorly understood. Here, we establish Drosophila melanogaster as a model system for the study of phosphate effects. We found that Drosophila larval development depends on the availability of phosphate in the medium. Conversely, life span is reduced when adult flies are cultured on high phosphate medium or when hemolymph phosphate is increased in flies with impaired Malpighian tubules. In addition, RNAi-mediated inhibition of MAPK-signaling by knockdown of Ras85D, phl/D-Raf or Dsor1/MEK affects larval development, adult life span and hemolymph phosphate, suggesting that some in vivo effects involve activation of this signaling pathway by phosphate. To identify novel genetic determinants of phosphate responses, we used Drosophila hemocyte-like cultured cells (S2R+) to perform a genome-wide RNAi screen using MAPK activation as the readout. We identified a number of candidate genes potentially important for the cellular response to phosphate. Evaluation of 51 genes in live flies revealed some that affect larval development, adult life span and hemolymph phosphate levels.

Restricting dietary magnesium accelerates ectopic connective tissue mineralization in a mouse model of pseudoxanthoma elasticum (Abcc6(-/-) )

Ectopic mineralization, linked to a number of diseases, is a major cause of morbidity and mortality in humans. Pseudoxanthoma elasticum (PXE) is a heritable multisystem disorder characterized by calcium phosphate deposition in various tissues. The mineral content of diet has been suggested to modify the disease severity in PXE. The aim of this study is to explore the role of diet with reduced magnesium in modifying tissue mineralization in a mouse model of PXE. Abcc6(-/-) mice were placed on either standard rodent diet (control) or an experimental diet low in magnesium at weaning (4 weeks) and examined for mineralization in the skin and internal organs at the ages of 1.5, 2 or 6 months by computerized morphometric analysis of histopathological sections and by chemical assay of calcium and phosphate. Abcc6(-/-) mice on experimental diet demonstrated an accelerated, early-onset mineralization of connective tissues, as compared to control mice. Wild-type or heterozygous mice on experimental diet did not show evidence of mineralization up to 6 months of age. All mice on experimental diet showed decreased urinary calcium, increased urinary phosphate and elevated parathyroid serum levels. However, no difference in bone density at 6 months of age was noted. Our findings indicate that the mineral content, particularly magnesium, can modify the extent and the onset of mineralization in Abcc6(-/-) mice and suggest that dietary magnesium levels may contribute to the phenotypic variability of PXE. The control of mineralization by dietary magnesium may have broader implications in general population in the context of vascular mineralization.

Zebrafish as a model system to study heritable skin diseases

Heritable skin diseases represent a broad spectrum of clinical manifestations due to mutations in ∼500 different genes. A number of model systems have been developed to advance our understanding of the pathomechanisms of genodermatoses. Zebrafish (Danio rerio), a freshwater vertebrate, has a well-characterized genome, the expression of which can be easily manipulated. The larvae develop rapidly, with all major organs having largely developed by 5-6 days post-fertilization, including the skin which consists at that stage of the epidermis comprising two cell layers and separated from the dermal collagenous matrix by a basement membrane zone. Here, we describe the use of morpholino-based antisense oligonucleotides to knockdown the expression of specific genes in zebrafish and to examine the consequent knockdown efficiency and skin phenotypes. Zebrafish can provide a useful model system to study heritable skin diseases.

Mouse Samd9l is not a functional paralogue of the human SAMD9, the gene mutated in normophosphataemic familial tumoral calcinosis

Normophosphataemic familial tumoral calcinosis, charac-terized by ectopic mineralization of skin, is caused by mutations in the SAMD9 gene located in human chromosome 7q21, next to a paralogous gene, SAMD9-like (SAMD9L). The mouse does not have a SAMD9 orthologue, Samd9, because it has been deleted during evolution owing to genomic rearrangements. It has been suggested that the mouse Samd9l gene serves as a functional paralogue of human SAMD9. In this study, we examined Samd9l knockout mice with respect to ectopic mineralization. We also crossed these mice with Abcc6(tm1JfK) mice, a model system to study pseudoxanthoma elasticum, to see whether the absence of the Samd9l gene modifies the mineralization process. Necropsy analysis of Samd9l(tm1Homy) mice revealed no evidence of ectopic mineralization, and deletion of the Samd9l gene in mice failed to modify the mineralization process on the Abcc6(tm1JfK) background. Collectively, the results suggest that mouse Samd9l is not a functional paralogue of human SAMD9.

Clinical consequences of mutations in sodium phosphate cotransporters

Three families of sodium phosphate cotransporters have been described. Their specific roles in human health and disease have not been defined. Review of the literature reveals that the type II sodium phosphate cotransporters play a significant role in transepithelial transport in a number of tissues including kidney, intestine, salivary gland, mammary gland, and lung. The type I transporters seem to play a major role in renal urate handling and mutations in these proteins have been implicated in susceptibility to gout. The ubiquitously expressed type III transporters play a lesser role in phosphate homeostasis but contribute to cellular phosphate uptake, mineralization, and inflammation. The recognition of species differences in the expression, regulation, and function of these transport proteins suggests an urgent need to find ways to study them in humans.

Cutaneous features of pseudoxanthoma elasticum in a patient with generalized arterial calcification of infancy due to a homozygous missense mutation in the ENPP1 gene

BACKGROUND

Pseudoxanthoma elasticum (PXE) manifests with cutaneous lesions consisting of yellowish papules coalescing into plaques of inelastic skin. Histopathology demonstrates accumulation of pleiomorphic elastic structures with progressive mineralization. The classic form of PXE is caused by mutations in the ABCC6 gene.

OBJECTIVES

A 2-year-old patient with PXE of the neck, inguinal folds and lower abdomen, and with extensive tissue mineralization, was evaluated for the underlying mutations in candidate genes known to be involved in ectopic mineralization disorders.

METHODS

The patient's genotype was studied by sequencing ABCC6, MGP and ENPP1 genes, encoding proteins which harbour mutations in ectopic mineralization disorders.

RESULTS

No pathogenetic mutations were found in the ABCC6 or MGP genes. Sequencing of ENPP1 disclosed a homozygous missense mutation, p.Y513C, associated with generalized arterial calcification of infancy.

CONCLUSIONS

This study demonstrates the presence of the cutaneous features of PXE in a genetically distinct disease, generalized arterial calcification of infancy, and thus expands the spectrum of PXE-related disorders.

Striking pathology gold: a singular experience with daily reverberations: sinonasal hemangiopericytoma (glomangiopericytoma) and oncogenic osteomalacia

Sinonasal hemangiopericytoma-like tumors(SNHPC)(glomangiopericytomas)were originally conceived as histologically similar to, but biologically distinct from, their soft tissue counterparts. Re-evaluation of "hemangiopericytiomas" has determined that SNHPC (glomangiopericytomas) represent bona-fide pericyte-derived tumors, whereas most soft tissue neoplasms previously designated as hemangiopericytomas represent cellular variants of solitary fibrous tumors or other lesions with a hemangiopericytomalike growth pattern. We present an interesting case of a woman with SNHPC (glomangiopericytomas) causing oncogenic osteomalacia, and discuss the recent advances in our understanding of phosphaturic mesenchymal tumors. This particular case is an example of "Striking Pathology Gold"-a situation where the pathologist actively guides the diagnostic process, and witnesses its repercussions. "Striking Pathology Gold" may be a rare event in one's career. However it serves to remind us of our place in the world as physicians. Working behind the scenes, we quietly change the course of countless individual destinies for the better.