Systemic sclerosis skin is a primed microenvironment for soft tissue calcification-a hypothesis

A rare form of calcinosis in patients with systemic sclerosis-myositis overlap: report of four cases

Objectives

Calcinosis is a well-described entity that occurs in patients with systemic sclerosis (SSc) and dermatomyositis (DM). Calcinosis in SSc typically occurs over pressure points and is usually nodular. We present a case series of four patients with SSc with a much rarer, diffuse form of calcinosis to illustrate this poorly recognized pattern of extensive and debilitating disease.

Methods

Four patients with SSc and extensive calcinosis were identified from patients attending a tertiary rheumatology centre in the preceding 3 years. Their electronic case notes, radiographic images and medical photographs were reviewed.

Results

All four patients had the diffuse cutaneous subtype of SSc (dcSSc) and additionally a myositis overlap. This was in the context of 102 of 461 (22%) patients with SSc whose clinical details had been recorded in the preceding 3 years having dcSSc. Their ages at diagnosis ranged from 27 to 65 years. Three were female, two were anti-Scl70 antibody positive, and two were anti-PMScl antibody positive. Development of calcinosis occurred between 1 and 6 years after onset of SSc. Plain radiography showed very extensive calcinosis in various sites, distributed in a pattern akin to sheets of calcium-containing deposits in the skin and subcutaneous tissue.

Conclusions

Although calcinosis is common in SSc, extensive sheet-like calcinosis is very rare. Our experience suggests that when this form of calcinosis does occur, this is in the context of the diffuse cutaneous subtype of disease and with myositis overlap. The four cases described should raise awareness of this unusual and extensive pattern of disease.

Calcinosis in systemic sclerosis

PURPOSE OF REVIEW

To provide updated information on the prevalence, pathogenesis, diagnostics, and therapeutics of calcinosis cutis associated with systemic sclerosis (SSc).

RECENT FINDINGS

Observational studies show ethnic and geographical differences in the prevalence of calcinosis. In addition to clinical and serological associations, biochemical studies and in-vivo models have attempted to explain theories behind its pathogenesis, including prolonged state of inflammation, mechanical stress, hypoxia, and dysregulation in bone and phosphate metabolism. Long-term use of proton pump inhibitors may increase the risk for calcinosis in SSc. Few single center observational studies have shown mild benefit with minocycline and topical sodium thiosulfate.

SUMMARY

Calcinosis cutis is the deposition of insoluble calcium in the skin and subcutaneous tissues. It affects up to 40% of SSc patients and causes significant morbidity. Long disease duration, features of vascular dysfunction, and osteoporosis have been associated with calcinosis. Altered levels of inorganic pyrophosphate and fibroblast growth factor-23 have been implicated in dysregulated phosphate metabolism that may lead to calcinosis in SSc. Plain radiography can help with diagnosis and quantifying the calcinosis burden. Surgical treatment remains the most effective therapy when feasible. At present, no medical therapies have proven efficacy in large randomized controlled trials.

Alterations in SAMD9, AHSG, FRG2C, and FGFR4 Genes in a Case of Late-Onset Massive Tumoral Calcinosis

Background/Objective

Tumoral calcinosis (TC) is a rare, arcane, and debilitating disorder of phosphate metabolism manifesting as hard masses in soft tissues. Primary hyperphosphatemic TC has been shown to be caused by pathogenic variants in the genes encoding FGF23, GALNT3, and KLOTHO. We report a case of massive TC mechanistically associated with phosphatonin resistance associated with heterozygous alterations in the sterile alfa motif domain-containing protein-9 gene (SAMD9), alfa 2-Heremans-Schmid glycoprotein gene (AHSG), FSHD region gene 2-family member-C gene (FRG2C), and fibroblast growth factor receptor-4 gene (FGFR4).

Case Report

A middle-aged Malay woman with systemic sclerosis presented with painful hard lumps of her axillae, lower limbs, and external genitalia. She was eucalcemic with mild hyperphosphatemia associated with reduced urinary phosphate excretion. Magnetic resonance imaging revealed calcified soft tissue masses. Paradoxically, the serum intact FGF23 level increased to 89.6 pg/mL, corroborated by Western blots, which also showed overexpression of sFRP4 and MEPE, consistent with phosphatonin resistance.

Discussion

Whole genome sequencing identified 2 heterozygous alterations (p.A454T and p.T479M) in SAMD9, 2 heterozygous alterations (p.M248T and p.S256T) in AHSG, a frameshift alteration (p.Arg156fs) in FRG2C, and a heterozygous alteration (p.G388R) in FGFR4, all of which are associated with calcinosis. Nonsynonymous alterations of FRP4 and MEPE were also detected.

Conclusion

This highlights that the simultaneous occurrence of alterations in several genes critical in phosphate homeostasis may trigger massive TC despite their heterozygosity. These findings should prompt functional studies in cell and animal models to reveal mechanistic insights in the pathogenesis of such crippling mineralization disorders.

Calciphylaxis and its co-occurrence with connective tissue diseases

Calciphylaxis, also known as calcific uremic arteriopathy, is a rare calcification syndrome that presents as ischemic skin necrosis and severe pain. It has a high mortality rate and is characterised by calcification of the small and medium arteries and micro-thrombosis. Calciphylaxis mainly occurs in patients with end-stage renal disease. In recent years, there have been an increasing number of cases of calciphylaxis associated with connective tissue diseases. Given the absence of clear diagnostic criteria for calciphylaxis thus far, an early diagnosis is crucial for designing an effective multidisciplinary treatment plan. In this article, we review the research progress on calciphylaxis and describe its characteristics in the context of connective tissue diseases.

Diagnosis and management of systemic sclerosis-related calcinosis

INTRODUCTION

Calcinosis is common in patients with systemic sclerosis (SSc) and refers to the sub-epidermal deposition of calcium salts in the skin. SSc-related calcinosis is associated with significant morbidity, including through cutaneous ulceration and predisposition to become infected.

AREAS COVERED

After briefly addressing aetiopathogenesis, we describe the clinical burden of SSc-associated calcinosis and provide a structured and practical clinical approach to diagnosis and assessment, including discussion of the role of different imaging modalities. The multi-faceted treatment of SSc-associated calcinosis is presented under three broad headings of 'general measures,' and 'medical treatment' and 'surgical treatment.' We adopted a narrative approach to identify relevant manuscripts to inform our review.

EXPERT OPINION

SSc-related calcinosis is an area of major unmet clinical need and for too long has been a neglected area of research. Safe and effective treatments are badly needed to improve patient quality of life and outcomes. To facilitate future clinical trials, we require increased understanding of pathogenesis (to inform selection of potential targeted therapies) and reliable outcome measures, including those which will measure the impact and severity of calcinosis from the patient perspective. International collaborative research is ongoing to develop outcome measures and treatments for this potentially devastating complication of SSc.

Calcinosis in systemic sclerosis

PURPOSE OF REVIEW

The aim of this study was to provide updated information on the prevalence, pathogenesis, diagnostics and therapeutics of calcinosis cutis associated with systemic sclerosis (SSc).

RECENT FINDINGS

Observational studies show ethnic and geographical differences in the prevalence of calcinosis. In addition to clinical and serological associations, biochemical studies and in-vivo models have attempted to explain theories behind its pathogenesis, including prolonged state of inflammation, mechanical stress, hypoxia and dysregulation in bone and phosphate metabolism. Long-term use of proton pump inhibitors may increase the risk for calcinosis in SSc. Few single-centre observational studies have shown mild benefit with minocycline and topical sodium thiosulfate.

SUMMARY

Calcinosis cutis is the deposition of insoluble calcium in the skin and subcutaneous tissues. It affects up to 40% of SSc patients and causes significant morbidity. Long disease duration, features of vascular dysfunction and osteoporosis have been associated with calcinosis. Altered levels of inorganic pyrophosphate and fibroblast growth factor-23 have been implicated in dysregulated phosphate metabolism that may lead to calcinosis in SSc. Plain radiography can help with diagnosis and quantifying the calcinosis burden. Surgical treatment remains the most effective therapy when feasible. At present, no medical therapies have proven efficacy in large randomized controlled trials.

Cancellous bone-like tissue replacement from calcinosis in patients with systemic sclerosis with multiple external root resorption

Calcinosis is frequently observed in patients with systemic sclerosis (SSc). The fundamental treatment of calcinosis has not yet been established. During follow-up, calcinosis in the subcutaneous surface is often spontaneously extracted or remains confined by fibrous tissues. We previously identified a new symptom in SSc patients, multiple external root resorption (MERR), and these patients had calcifications in the nasal spine. Here, we report for the first time that calcinosis at the nasal spine in patients with MERR can be replaced by cancellous bone-like tissue. Patients 1 and 2 were a 62-year-old Japanese female and a 45-year-old Japanese female (respectively) with MERR who had been previously treated for SSc (Patient 1: limited type, positive for anti-centromere antibody; Patient 2: diffuse type, positive for anti-Scl70 and anti-SS-A antibodies). Patient 3 was a 57-year-old female with MERR who had been previously treated for SSc (diffuse type, positive anti-Scl-70 antibody) and underwent denosumab injection for osteoporosis. Cone-beam computed tomography (CBCT) and CT images in the calcifications at the nasal spine in Patient 1 and 2 were replaced with cancellous bone-like tissue, but not in Patient 3. Serum laboratory examination was performed to assess the systemic bone disease. All three patients had normal clinical data within the references, apart from slightly higher 1,25-dihydroxyvitamin D levels in Patient 1. SSc patients with calcinosis in the maxillofacial area need to be examined carefully for bone replacement using CBCT or CT.