Parathyroid-hormone-related peptide in hematologic malignancies

An infant developing hypercalcemia and hypophosphatemia due to the use of exclusively almond milk

OBJECTIVES

Plant-based milk alternatives are increasingly utilized in children with cow milk allergy, lactose intolerance, and personal preference. However, notable differences exist in mineral content between cow milk and plant-based alternatives. Almond milk, in particular, varies in mineral and caloric content across different brands. This case report highlights a toddler who developed hypercalcemia and hypophosphatemia attributed to almond milk consumption.

CASE PRESENTATION

A fourteen-month-old girl with a history of biliary atresia underwent liver transplant at seven months of age. She was exclusively consuming almond milk for two months prior to presentation. She was admitted to the hospital for severe hypercalcemia (14.6 mg/dL) and hypophosphatemia (1.6 mg/dL). She had elevated random urine calcium to creatinine ratio (2.56 mg/g) and low urine phosphorus to creatinine ratio (<0.44 mg/g) were noted. Parathyroid hormone (PTH) level was appropriately suppressed (<6 pg/mL), while 1,25 dihydroxyvitamin D level was slightly elevated at 88 pg/mL. Initial management included intravenous fluids, followed by a switch to a formula with higher phosphorus and lower calcium concentrations. The patient was discharged after six days with normalized calcium and phosphorus levels, which remained within the normal range.

CONCLUSIONS

Although plant-derived milk serves as a viable alternative to cow milk, careful consideration of mineral content, particularly in infants and toddlers, is imperative. Sole reliance on almond milk for nutritional needs in this population is not recommended. Caregivers should be informed about the potential risks associated with almond milk consumption in infants and toddlers.

PTHrP Regulates Fatty Acid Metabolism via Novel lncRNA in Breast Cancer Initiation and Progression Models

Parathyroid hormone-related peptide (PTHrP) is the primary cause of malignancy-associated hypercalcemia (MAH). We previously showed that PTHrP ablation, in the MMTV-PyMT murine model of breast cancer (BC) progression, can dramatically prolong tumor latency, slow tumor growth, and prevent metastatic spread. However, the signaling mechanisms using lineage tracing have not yet been carefully analyzed. Here, we generated Pthrpflox/flox; Cre+ mT/mG mice (KO) and Pthrpwt/wt; Cre+ mT/mG tumor mice (WT) to examine the signaling pathways under the control of PTHrP from the early to late stages of tumorigenesis. GFP+ mammary epithelial cells were further enriched for subsequent RNA sequencing (RNAseq) analyses. We observed significant upregulation of cell cycle signaling and fatty acid metabolism in PTHrP WT tumors, which are linked to tumor initiation and progression. Next, we observed that the expression levels of a novel lncRNA, GM50337, along with stearoyl-Coenzyme A desaturase 1 (Scd1) are significantly upregulated in PTHrP WT but not in KO tumors. We further validated a potential human orthologue lncRNA, OLMALINC, together with SCD1 that can be regulated via PTHrP in human BC cell lines. In conclusion, these novel findings could be used to develop targeted strategies for the treatment of BC and its metastatic complications.

Cancer-related hypercalcemia and potential treatments

Cancer-related hypercalcemia is a common finding typically seen in patients with advanced cancer and occurs in about 20 to 30 percent of cases. The most common cause of hypercalcemia in hospitalized patients is hypercalcemia due to malignancy.This clinical problem is seen in patients with both solid tumors and patients with hematologic malignancies. Hypercalcemia is associated with a poor prognosis in oncology patients. This pathologic condition can occur due to many different mechanisms but is usually caused by abnormal calcium use resulting from bone resorption, intestinal absorption, or renal excretion. Hypercalcemia may present with a wide range of symptoms ranging from gastrointestinal system symptoms to neurologic symptoms. Timely diagnosis and initiation of treatment by the physician significantly reduce the risk of complications. Treatment aims to decrease serum calcium by increasing calciuresis, decreasing bone resorption, and decreasing intestinal calcium absorption. The mainstays of treatment are IV hydration, bisphosphonates and calcitonin, denosumab, and in some patients, prednisone, and cinacalcet. Patients with underlying advanced kidney disease and refractory severe hypercalcemia should be evaluated for hemodialysis. Every physician dealing with oncology patients should know the fastest and most effective management of hypercalcemia. We aimed to contribute in this sense.

Immunoarray Measurements of Parathyroid Hormone-Related Peptides Combined with Other Biomarkers to Diagnose Aggressive Prostate Cancer

Parathyroid hormone-related peptide (PTHrP) is related to bone metastasis and hypercalcemia in prostate and breast cancers and should be an excellent biomarker for aggressive forms of these cancers. Current clinical detection protocols for PTHrP are immunoradiometric assay and radioimmunoassay but are not sensitive enough to detect PTHrPs at early stages. We recently evaluated a prostate cancer biomarker panel, including serum monocyte differentiation antigen (CD-14), ETS-related gene protein, pigment epithelial-derived factor, and insulin-like growth factor-1, with promise for identifying aggressive prostate cancers. This panel predicted the need for patient biopsy better than PSA alone. In the present paper, we report an ultrasensitive microfluidic assay for PTHrPs and evaluate their diagnostic value and the value of including them with our prior biomarker panel to diagnose aggressive forms of prostate cancer. The immunoarray features screen-printed carbon sensor electrodes coated with 5 nm glutathione gold nanoparticles with capture antibodies attached. PTHrPs are bound to a secondary antibody attached to a polyhorseradish peroxidase label and delivered to the sensors to provide high sensitivity when activated by H₂O₂ and a mediator. We obtained an unprecedented 0.3 fg mL^-1 limit of detection for PTHrP bioactive moieties PTHrP 1-173 and PTHrP 1-86. We also report the first study of PTHrPs in a large serum pool to identify aggressive malignancies. In assays of 130 human patient serum samples, PTHrP levels distinguished between aggressive and indolent prostate cancers with 83-91% clinical sensitivity and 78-96% specificity. Logistic regression identified the best predictive model as a combination of PTHrP 1-86 and vascular endothelial growth factor-D. PTHrP 1-173 alone also showed a high ability to differentiate aggressive and indolent cancers.

Parathyroid hormone-related protein (PTHrP) and malignancy

PTHrP (parathyroid hormone related protein) is an important mediator of malignancy-related tumor progression and hypercalcemia that shares considerable homology and functionality with parathyroid hormone. In this chapter, we review what has been elucidated to date regarding PTHrP's role in malignancies. Starting with a review of calcium metabolism and regulation, we then summarize the discovery and structure of PTHrP and development of sensitive immunoassays for specific measurement. Subsequently, we explore its role in tumor progression, with emphasis on the primary tumor as well as skeletal and non-osseus metastases. We then consider the clinical implications of PTHrP in cancer before concluding with a discussion of both established and potential treatments for malignancy associated hypercalcemia and bone metastases.

Pathophysiology of Hypercalcemia

Extracellular calcium is normally tightly regulated by parathyroid hormone (PTH), 1,25-dihydroxyvitamin D, as well as by calcium ion (Ca⁺⁺) itself. Dysregulated PTH production leading to hypercalcemia occurs most commonly in sporadic primary hyperparathryoidism (PHPT) but may also result from select genetic mutations in familial disorders. Parathyroid hormone-related protein shares molecular mechanisms of action with PTH and is the most common cause of hypercalcemia of malignancy. Other cytokines and mediators may also cause resorptive hypercalcemia once bone metastases have occurred. Less commonly, extrarenal production of calcitriol can occur in malignancies and in infectious and noninfectious inflammatory conditions and can cause hypercalcemia.

Parathyroid hormone‐related protein inhibition blocks triple‐negative breast cancer expansion in bone through epithelial to mesenchymal transition reversal

Parathyroid hormone‐related protein (PTHrP) plays a major role in skeletal metastasis but its action mechanism has not been fully defined. We previously demonstrated the crucial importance of PTHrP in promoting mammary tumor initiation, growth, and metastasis in a mouse model with a mammary epithelium‐targeted Pthlh gene ablation. We demonstrate here a novel mechanism for bone invasion involving PTHrP induction of epithelial to mesenchymal transition (EMT) and cancer stem cells (CSCs) regulation. Clustered regularly interspaced short palindromic repeats (CRISPR)‐mediated Pthlh gene ablation was used to study EMT markers, phenotype, and invasiveness in two triple‐negative breast cancer (TNBC) cell types (established MDA‐MB‐231 and patient‐derived PT‐TNBC cells). In vitro, Pthlh ablation in TNBC cells reduced EMT markers, mammosphere‐forming ability, and CD44^high/CD24^low cells ratio. In vivo, cells were injected intratibially into athymic nude mice, and therapeutic treatment with our anti‐PTHrP blocking antibody was started 2 weeks after skeletal tumors were established. In vivo, compared to control, lytic bone lesion from Pthlh ‐ablated cells decreased significantly over 2 weeks by 27% for MDA‐MB‐231 and by 75% for PT‐TNBC‐injected mice (p < 0.001). Micro‐CT (μCT) analyses also showed that antibody therapy reduced bone lytic volume loss by 52% and 48% for non‐ablated MDA‐MB‐231 and PT‐TNBC, respectively (p < 0.05). Antibody therapy reduced skeletal tumor burden by 45% and 87% for non‐ablated MDA‐MB‐231 and PT‐TNBC, respectively (p < 0.002) and caused a significant decrease of CSC/EMT markers ALDH1, vimentin, and Slug, and an increase in E‐cadherin in bone lesions. We conclude that PTHrP is a targetable EMT molecular driver and suggest that its pharmacological blockade can provide a potential therapeutic approach against established TNBC‐derived skeletal lesions. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

PTHrP Drives Pancreatic Cancer Growth and Metastasis and Reveals a New Therapeutic Vulnerability

Pancreatic cancer metastasis is a leading cause of cancer-related deaths, yet very little is understood regarding the underlying biology. As a result, targeted therapies to inhibit metastasis are lacking. Here, we report that the parathyroid hormone-related protein (PTHrP encoded by PTHLH) is frequently amplified as part of the KRAS amplicon in patients with pancreatic cancer. PTHrP upregulation drives the growth of both primary and metastatic tumors in mice and is highly enriched in pancreatic ductal adenocarcinoma metastases. Loss of PTHrP-either genetically or pharmacologically-dramatically reduces tumor burden, eliminates metastasis, and enhances overall survival. These effects are mediated in part through a reduction in epithelial-to-mesenchymal transition, which reduces the ability of tumor cells to initiate metastatic cascade. Spp1, which encodes osteopontin, is revealed to be a downstream effector of PTHrP. Our results establish a new paradigm in pancreatic cancer whereby PTHrP is a driver of disease progression and emerges as a novel therapeutic vulnerability. SIGNIFICANCE: Pancreatic cancer often presents with metastases, yet no strategies exist to pharmacologically inhibit this process. Herein, we establish the oncogenic and prometastatic roles of PTHLH, a novel amplified gene in pancreatic ductal adenocarcinoma. We demonstrate that blocking PTHrP activity reduces primary tumor growth, prevents metastasis, and prolongs survival in mice.This article is highlighted in the In This Issue feature, p. 1601.

Mechanisms of Hypercalcemia in Non-Hodgkin Lymphoma and Associated Outcomes: A Retrospective Review

INTRODUCTION

The etiology of hypercalcemia in non-Hodgkin lymphoma (NHL) has been most often attributed to either elevated serum levels of 1,25-dihydroxycholecalciferol (calcitriol) or parathyroid-related protein (PTHrP). In a single-center retrospective review, we evaluated the incidence of, and outcomes associated with, hypercalcemia in NHL.

PATIENTS AND METHODS

The medical records of patients with a histologically confirmed diagnosis of NHL and ≥ 1 episode of hypercalcemia were evaluated for demographic and lymphoma-specific factors, including the response to therapy and overall survival.

RESULTS

Fifty-four patients with NHL met the inclusion criteria. Most patients (57.4%) had diffuse large B-cell lymphoma, of which, 70% were the nongerminal center subtype. Approximately one half (42.6%) of the included patients had undergone serologic investigation into the etiology of hypercalcemia; however, only 17 patients (31.5%) had both a serum PTHrP and a calcitriol level properly collected. Of the 17 cases for which both a serum calcitriol and a PTHrP were collected, most (61.1%) were found to have neither an elevation of serum calcitriol nor an elevation of PTHrP. The degree of calcitriol elevation correlated with worse progression-free survival (P = .04) but not overall survival.

CONCLUSION

The major mechanism by which NHL patients develop hypercalcemia is not mediated by calcitriol or PTHrP. Hypercalcemia is most prevalent in patients with diffuse large B-cell lymphoma of the nongerminal cell subtype. Patients with calcitriol-mediated hypercalcemia showed a trend toward worse outcomes, suggesting that calcitriol might be a marker of high-grade lymphoma, transformation to such, or a surrogate for more advanced disease.

Calcitriol-mediated hypercalcemia in a patient with bilateral adrenal non-Hodgkin's B-cell lymphoma case report

Calcitriol-mediated hypercalcemia is a frequent manifestation of hematological malignancies. However, there are a few reports of cases presenting with increased angiotensin-converting enzyme (ACE) level, which suggests a possible mechanism similar to that of granulomatous diseases. We present a patient with hypercalcemia, normal parathyroid hormone, and parathyroid hormone-related protein levels but high calcitriol and ACE levels that, after further investigation, was diagnosed with bilateral adrenal non-Hodgkin's B-cell lymphoma. Primary adrenal lymphoma represents only 1% of all non-Hodgkin's lymphomas and is usually asymptomatic but should be considered by clinicians among the malignancies that cause calcitriol-mediated hypercalcemia.

Waldenstroms Macroglobulinemia Patient Presenting with Rare 'lytic' Lesions and Hypercalcemia: A Diagnostic Dilemma

Waldenstroms macroglobulinemia (WM) is an uncommon B-cell lymphoproliferative neoplasm characterized by lymphoplasmacytic cells infiltrating the Bone Marrow, along with demonstration of an IgM monoclonal gammopathy in the serum. Lytic lesions are considered one of the basis for differentiating a patient of Multiple Myeloma (MM) and WM. However, very few cases have been reported with a patient presenting with lytic lesions in a WM patient, thereby, complicating the disease. By finding the extent of these lytic lesions and bone involvement, Not only can we signify the presence or absence of bone lesions, but we can also direct the more efficient use of skeletal X-rays for documentation of the extent, location, and response of bone abnormalities to interventional chemotherapy and radiation therapy. Our case was mimicking the classic case of MM. Using the International Criteria for diagnosis for WM, diagnosis for MM was excluded and diagnosis for WM was made. After two weeks of therapy, the patient showed marked clinical improvement.

Epithelial-mesenchymal transition-related microRNA-200s regulate molecular targets and pathways in renal cell carcinoma

Our recent studies of microRNA (miRNA) expression signatures demonstrated that the epithelial-mesenchymal transition (EMT)-related microRNA-200 family (miR-200s: miR-200a/b/c, miR-141 and miR-429) were significantly downregulated in renal cell carcinoma (RCC) and putative tumor-suppressive miRNAs in RCC. In this study, our aim was to investigate the functional significance of the miR-200s in cancer cells and to identify novel miR-200s-regulated molecular targets and pathways in RCC. Expression levels of all the miR-200s members were significantly downregulated in human RCC tissues compared with normal renal tissues. Restoration of mature miR-200s in RCC cell line resulted in significant inhibition of cell proliferation and migration, suggesting that miR-200s function as tumor suppressors in RCC. Furthermore, we utilized gene expression analysis and in silico database analysis to identify miR-200s-regulated molecular targets and pathways in RCC. The miR-200s was categorized into two groups, according to their seed sequences, miR-200b/c/429 and miR-200a/141. Our data demonstrated that the 'Focal adhesion' and 'ErbB signaling' pathways were significantly regulated by miR-200b/c/429 and miR-200a/141, respectively. The identification of novel tumor-suppressive miR-200s-regulated molecular targets and pathways has provided new insights into RCC oncogenesis and metastasis.

Mechanisms and treatment of hypercalcemia of malignancy

PURPOSE OF REVIEW

Hypercalcemia of malignancy is a common paraneoplastic syndrome and a frequent complication of advanced breast and lung cancer, and multiple myeloma. The development of this malignancy complication often purports a poor prognosis. Thorough evaluation to establish the cause of hypercalcemia is essential because some patients may actually have undiagnosed primary hyperparathyroidism.

RECENT FINDINGS

Production of humoral factors by the primary tumor, collectively known as humoral hypercalcemia of malignancy (HHM), is the mechanism responsible for 80% of cases. The vast majority of HHM is caused by tumor-produced parathyroid hormone-related protein followed by infrequent tumor production of 1,25-dihydroxyvitamin D and parathyroid hormone. The remaining 20% of cases are caused by bone metastasis with consequent bone osteolysis and release of skeletal calcium. Key therapies are saline hydration to promote calciuresis and bisphosphonates to reduce pathologic osteoclastic bone resorption. Calcitonin and glucocorticoids, especially in 1,25-dihydroxyvitamin D-mediated HHM, also have calcium-lowering effects.

SUMMARY

Recent discoveries on mechanisms of malignancy-associated hypercalcemia highlight the critical role of the osteoclast. Bisphosphonates and other novel therapies being evaluated in clinical trial target this bone-resorbing cell type and provide effective and durable serum calcium reduction.

PTHrP drives breast tumor initiation, progression, and metastasis in mice and is a potential therapy target

Parathyroid hormone-related protein (PTHrP) is a secreted factor expressed in almost all normal fetal and adult tissues. It is involved in a wide range of developmental and physiological processes, including serum calcium regulation. PTHrP is also associated with the progression of skeletal metastases, and its dysregulated expression in advanced cancers causes malignancy-associated hypercalcemia. Although PTHrP is frequently expressed by breast tumors and other solid cancers, its effects on tumor progression are unclear. Here, we demonstrate in mice pleiotropic involvement of PTHrP in key steps of breast cancer - it influences the initiation and progression of primary tumors and metastases. Pthrp ablation in the mammary epithelium of the PyMT-MMTV breast cancer mouse model caused a delay in primary tumor initiation, inhibited tumor progression, and reduced metastasis to distal sites. Mechanistically, it reduced expression of molecular markers of cell proliferation (Ki67) and angiogenesis (factor VIII), antiapoptotic factor Bcl-2, cell-cycle progression regulator cyclin D1, and survival factor AKT1. PTHrP also influenced expression of the adhesion factor CXCR4, and coexpression of PTHrP and CXCR4 was crucial for metastatic spread. Importantly, PTHrP-specific neutralizing antibodies slowed the progression and metastasis of human breast cancer xenografts. Our data identify what we believe to be new functions for PTHrP in several key steps of breast cancer and suggest that PTHrP may constitute a novel target for therapeutic intervention.

Parathyroid hormone related protein (PTHrP) in tumor progression

Parathyroid hormone-related protein (PTHrP) is widely expressed in fetal and adult tissues and is a key regulator for cellular calcium transport and smooth muscle cell contractility, as well as a crucial control factor in cell proliferation, development and differentiation. PTHrP stimulates or inhibits apoptosis in an autocrine/paracrine and intracrine fashion, and is particularly important for hair follicle and bone development, mammary epithelial development and tooth eruption. PTHrP's dysregulated expression has traditionally been associated with oncogenic pathologies as the major causative agent of malignancy-associated hypercalcemia, but recent evidence revealed a driving role in skeletal metastasis progression. Here, we demonstrate that PTHrP is also closely involved in breast cancer initiation, growth and metastasis through mechanisms separate from its bone turnover action, and we suggest that PTHrP as a facilitator of oncogenes would be a novel target for therapeutic purposes.

[Humoral hypercalcemia revealing a malignant non hodgkin lymphoma]

INTRODUCTION

Hypercalcemia is a rare complication of non-Hodgkin lymphoma. Usually, hypercalcemia occurs late in the disease course, except for high-grade lymphoma. Most often hypercalcemia is related to excessive level of circulating PTH-rP or sometimes, 1,25(OH)2D3. Concomitant high plasmatic concentration of PTH-rP and 1,25(OH)2D3 is uncommon.

EXEGESIS

We report the case of a 82-year-old man who presented with abdominal pain and weight loss, leading to the diagnosis of diffuse large-B-cell lymphoma (high-grade lymphoma) associated with symptomatic hypercalcemia (3.21mmol/l). PTH-rP and 1,25(OH)2D3 plasmatic levels were high. Calcium concentration was normalized with glucocorticoids and sequential chemotherapy.

CONCLUSION

This case report confirms that hypercalcemia, as consequence of excessive plasmatic level of PTH-rP secreted by tumoral cells, can occur early in the course of high-grade lymphoma. Glucocorticoids and chemotherapy are the best treatment options.

Parathyroid hormone-related protein is reduced in severe chronic heart failure

In the cardiovascular system, parathyroid hormone-related peptide (PTHrP) is expressed in various cells such as cardiac vascular smooth muscle cells, coronary endothelial cells and cardiomyocytes and acts as an autocrine/paracrine substance. We compared PTHrP levels in 35 consecutive patients with severe CHF (33 male, mean age 66.2 +/- 8.9 years) with 26 normal controls (24 male, mean age 63.1 +/- 8.6 years). PTHrP levels were reduced in severe CHF patients (11.10 +/- 1.37 fmol/ml) compared with the controls (20.62 +/- 3.30 fmol/ml, p = 0.005). PTHrP values decreased as a function of New York Heart Association classification. These results suggest that PTHrP levels decrease in proportion to the severity of heart failure and could potentially be used to monitor progression of disease non-invasively.

Non-Hodgkin's lymphoma presenting as multiple bone lesions and hypercalcemia

We report a rare case of a patient with non-Hodgkin's lymphoma who developed multiple bone lesions and hypercalcemia. A 50-year-old woman complained of drowsiness and multiple bone pain on admission. Radiographic examination revealed multiple bone fractures and osteolytic lesions. She was diagnosed with diffuse large B cell lymphoma by biopsy of an inguinal lymph node. Elevation of parathyroid hormone-related protein (PTHrP) and hypercalcemia were confirmed pretreatment, and those serum levels decreased during chemotherapy for lymphoma. However, the disease was resistant to chemotherapy combined with rituximab. These findings suggest that hypercalcemia is associated with PTHrP and the prognosis of patients with bone lymphoma in advanced stage is poor, although it is thought to be a relatively favorable prognosis in localized primary lymphoma of bone.

Current management strategies for hypercalcemia

The two most common causes of hypercalcemia are primary hyperparathyroidism and neoplastic disease. Parathyroidectomy is the only curative intervention for the former condition. In the rare cases of patients with primary hyperparathyroidism who present with clinical symptoms due to their hypercalcemia, pharmacological treatment may be required. Fluid repletion and intravenous (IV) administration of bisphosphonates are recommended in the literature. Calcium receptor agonists (calcimimetic agents) are at the present time only available for use within clinical trials. Cancer patients usually present with symptoms of hypercalcemia. Rapid institution of antihypercalcemic treatment is essential in preventing life-threatening deterioration. Fluid repletion and administration of bisphosphonates are the treatment mainstays in hypercalcemia of malignancy. Five bisphosphonates are currently licensed in Europe for treatment of tumor-associated hypercalcemia: etidronate, clodronate, pamidronate, ibandronate, and zoledronate. In the US, pamidronate and zoledronate are licensed for use in this indication. Bisphosphonates containing nitrogen atoms (e.g. pamidronate, ibandronate, and zoledronate) are more potent than those without (e.g. etidronate, clodronate, and tiludronate). In patients with malignant hypercalcemia, the efficacy of the individual bisphosphonate depends on dose administered and initial serum calcium concentration. At present, pamidronate has been studied in the greatest number of investigations and in the largest number of patients. In the literature, the efficacy of pamidronate in restoring normocalcemia ranges between 40% and 100%, depending on the dose used and baseline serum calcium concentration. More recently, one study reported that pamidronate was inferior to zoledronate. In this study, the duration of response was also longer in the two zoledronate groups (30 and 40 days) than in the pamidronate group (17 days). The most serious adverse events of bisphosphonates concern renal function. Increases in serum creatinine levels have been more frequently reported following treatment of tumor-associated hypercalcemia with etidronate (8%) and clodronate (5%) than with the nitrogen-containing bisphosphonates pamidronate (2%) and ibandronate (1%). The frequency of increases in serum creatinine levels following treatment with zoledronate is difficult to estimate. Administration of the nitrogen-containing bisphosphonates has been associated with transient (usually mild) fever, lymphocytopenia, malaise, and myalgias. These events occur within 36 hours of the first dose and are self-limiting. Hypocalcemia occurs in up to 50% of patients treated with bisphosphonates for hypercalcemia of malignancy, although symptomatic hypocalcemia is rare. The toxicity and low efficacy of plicamycin (mithramycin) mean that use of this agent should be restricted to patients with hypercalcemia of malignancy who fail to respond to IV bisphosphonates. Calcitonin is characterized by good tolerability but poor efficacy in normalizing the serum calcium level. However, a major advantage of calcitonin is the acute onset of the hypocalcemic effect, which contrasts with the delayed but more pronounced effect of bisphosphonates. Combination calcitonin and bisphosphonate treatment may therefore be of value when rapid reduction of serum calcium is warranted. Gallium nitrate may be a valuable treatment for hypercalcemia of malignancy. It is characterized by high efficacy and few adverse events apart from renal toxicity (10% of cases). However, data are very limited and further trials are necessary.

Symptomatic hypercalcemia as presenting manifestation of lymphoma in a patient with acquired immunodeficiency syndrome

Hypercalcemia can be an uncommon manifestation of various infections and malignancies in HIV-positive patients. A case of severe symptomatic hypercalcemia as the first sign of non-Hodgkin's lymphoma in a patient found later to be HIV positive is presented. Differential diagnosis of calcium disorders should include test for HIV and underlying conditions including lymphoma in the diagnostic work up.

Increased expression of 25-hydroxyvitamin D-1alpha-hydroxylase in dysgerminomas: a novel form of humoral hypercalcemia of malignancy

Humoral hypercalcemia of malignancy (HHM) is a common paraneoplastic disorder usually associated with increased synthesis of parathyroid hormone-related peptide (PTHrP). Unlike non-cancer forms of hypercalcemia, HHM does not routinely involve increased circulating levels of the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Dysgerminomas are a notable exception to this rule, previous reports having described hypercalcemia with elevated serum 1,25(OH)2D3. To investigate the etiology of this form of HHM we have characterized expression and activity of the enzyme that catalyzes synthesis of 1,25(OH)2D3, 25-hydroxyvitamin D-1alpha-hydroxylase (1alpha-hydroxylase), in a collection of 12 dysgerminomas. RT-PCR analyses indicated that mRNA for 1alpha-hydroxylase was increased 222-fold in dysgerminomas compared to non-tumor ovarian tissue. Parallel enzyme assays in tissue homogenates showed that dysgerminomas produced fivefold higher levels of 1,25(OH)2D3 compared to normal ovarian tissue. Immunolocalization studies indicated that 1alpha-hydroxylase was expressed by both tumor cells and by macrophages within the inflammatory cell infiltrate associated with dysgerminomas. The immunological nature of the increased 1,25(OH)2D3 production observed in dysgerminomas was further emphasized by correlation between expression of 1alpha-hydroxylase and the endotoxin recognition factors CD14 and toll-like receptor 4 (TLR4). These data suggest that inflammatory mechanisms associated with dysgerminomas are the underlying cause of the increased expression and activity of 1alpha-hydroxylase associated with these tumors. We further postulate that this autocrine/paracrine action of 1alpha-hydroxylase may lead to increased circulating levels of 1,25(OH)2D3 and a form of HHM which is distinct from that seen with PTHrP-secreting tumors.

Parathyroid hormone-related peptide and survival of patients with cancer and hypercalcemia

PURPOSE

Parathyroid hormone-related peptide (PTHrP) is the predominant cause of malignancy-associated hypercalcemia. However, its prognostic utility is unclear. We aimed to determine the prognostic value of serum PTHrP levels in patients who had hypercalcemia associated with malignancy.

METHODS

In this prospective case series, we evaluated 76 patients with a diagnosis of cancer and hypercalcemia (serum calcium level >/=10.3 mg/dL on at least two occasions). PTHrP levels >/=1 pmol/L were considered elevated. We used multivariate Cox regression analysis to identify factors associated with mortality.

RESULTS

Fifty patients (66%) died during follow-up. In a multivariate analysis, higher pretreatment calcium levels and elevated PTHrP levels were associated with increased mortality, with effects of PTHrP varying by age (P = 0.03). Survival was associated with pretreatment calcium levels both in patients over 65 years of age (hazard ratio [HR] per mg/dL = 1.5; 95% confidence interval [CI]: 1.2 to 1.8; P <0.001) and in patients aged 65 years or less (HR = 1.3; 95% CI: 1.1 to 1.5; P = 0.003). Adjusted for pretreatment calcium levels, elevated PTHrP levels were associated with increased mortality in patients aged </=65 years (HR = 3.8; 95% CI: 1.6 to 8.8; P = 0.002), but not in older patients (HR = 0.7; 95% CI: 0.3 to 1.9; P = 0.51).

CONCLUSION

PTHrP is a useful prognostic factor in malignancy-associated hypercalcemia, at least in patients aged </=65 years.

Parathyroid hormone-related protein (PTHrP) produced by dog lymphoma cells

Parathyroid hormone-related protein (PTHrP) was investigated in a canine lymphoma case with hypercalcemia by means of immunoradiomentric assay (IRMA) and molecular analysis. The plasma calcium level of the patient dog was 13.7 mg/dl. The PTHrP concentration examined by IRMA was 6.1 pmol/L in the plasma sample from the dog, but it was undetectable (< 1.1 pmol/L) in plasma samples from 4 lymphoma cases without hypercalcemia or 5 normal dogs. The PTHrP concentration examined in the culture supernatant of the lymphoma cells from this case was 1.3 pmol/L, whereas those of the lymphoma cells from a lymphoma case without hypercalcemia was undetectable. PTHrP mRNA was clearly detected not only in the lymphoma cells from this dog with hypercalcemia but also in lymphoma cells from 4 lymphoma cases without hypercalcemia and 2 canine lymphoma cell lines.

Ca(2+)-sensing receptor expression and PTHrP secretion in PC-3 human prostate cancer cells

Prostate cancer metastasizes frequently to bone. Elevated extracellular calcium concentrations ([Ca(2+)](o)) stimulate parathyroid hormone-related protein (PTHrP) secretion from normal and malignant cells, potentially acting via the [Ca(2+)](o)-sensing receptor (CaR). Because prostate cancers produce PTHrP, if high [Ca(2+)](o) stimulates PTHrP secretion via the CaR, this could initiate a mechanism whereby osteolysis caused by bony metastases of prostate cancer promotes further bone resorption. We investigated whether the prostate cancer cell lines LnCaP and PC-3 express the CaR and whether polycationic CaR agonists stimulate PTHrP release. Both PC-3 and LnCaP prostate cancer cell lines expressed bona fide CaR transcripts by Northern analysis and RT-PCR and CaR protein by immunocytochemistry and Western analysis. The polycationic CaR agonists [Ca(2+)](o), neomycin, and spermine each concentration dependently stimulated PTHrP secretion from PC-3 cells, as measured by immunoradiometric assay, with maximal, 3.2-, 3.6-, and 4.2-fold increases, respectively. In addition, adenovirus-mediated infection of PC-3 cells with a dominant negative CaR construct attenuated high [Ca(2+)](o)-evoked PTHrP secretion, further supporting the CaR's mediatory role in this process. Finally, pretreating PC-3 cells with transforming growth factor (TGF)-beta(1) augmented both basal and high [Ca(2+)](o)-stimulated PTHrP secretion. Thus, in PTHrP-secreting prostate cancers metastatic to bone, the CaR could initiate a vicious cycle, whereby PTHrP-induced bone resorption releases [Ca(2+)](o) and TGF-beta stored within bone, further increasing PTHrP release and osteolysis.

Hypercalcemia after High-Dose Chemoradiotherapy for Refractory Multiple Myeloma; Subject Heading

A 43-year-old man with refractory myeloma underwent allogeneic bone marrow transplantation from his HLA-matched sibling. He was conditioned with TBI (12 Gy) followed by melphalan (140 mg/m(2) ). Immediately after conditioning was initiated, he began complaining of severe lumbago, and the level of serum calcium rose from 2.25 to 3.34 mmol / l. However, the biochemical markers for tumor-lysis syndrome such as potassium, uric acid, and lactic dehydrogenase remained unchanged. Hydration with saline and pamidronate were started, but he developed acute renal failure requiring hemodialysis for 3 weeks. His plasma parathyroid hormonerelated protein (PTHrP)-NH2-terminal (3.9 pmol/l) and serum PTHrP-C-terminal (125.0 pmol / l) levels markedly increased immediately after conditioning. These results suggested that the increased release of PTHrP from myeloma cells, which resulted from destruction of myeloma cells by conditioning, was the primary contributes to the occurrence of hypercalcemia. We should be aware of the occurrence of hypercalcemia when high-dose therapy is to be given to patients with refractory myeloma.

Expression and in vitro modification of parathyroid hormone-related protein (PTHrP) and PTH/PTHrP-receptor in human myeloma cells

To elucidate the role of PTHrP in myeloma, we examined the expression levels of PTHrP and its receptor in human myeloma cell lines and clinical specimens from 13 myeloma cases. In vitro modification of PTHrP expression and production induced by TGF-beta and PMA in PTHrP expressing myeloma cell lines was also investigated. PTHrP expression was detected in six out of seven myeloma cell lines with an inverse correlation with the expression of its receptor, and in 10 out of 13 clinical specimens in varying degrees. The PTHrP expression and secretion into culture medium were enhanced by supplemental TGF-beta and PMA. PMA also seemed to affect PTHrP upregulation via TGF-beta activation. The fundamental role of PTHrP in bone lesions and hypercalcemia in myeloma may be important to consider even during the initial phase of the disease and particularly in the progression of bone complications with hypercalcemia.

Hypercalcemia as the presenting feature of t-cell lymphoid blast crisis of ph-positive chronic myeloid leukemia

Hypercalcemia is a rare complication of chronic myeloid leukemia (CML), usually seen in the accelerated or blastic phases of the disease and associated with a poor prognosis. T-cell lymphoid phenotype is also an infrequent finding in the blast crisis (BC) of CML. A CML patient who had hypercalcemia as the presenting feature of a T-cell BC is reported. She was a 78 year-old woman who, at four months of CML diagnosis, developed weakness, bone pain, and mental confusion, with hypercalcemia being subsequently found. Although the peripheral blood and bone marrow were consistent with the chronic phase of CML, mediastinal enlargement, a soft tissue mass adjacent to the iliac bone, and multiple osteolytic lesions were seen. Serum levels of parathyroid hormone (PTH) and PTH-related peptide were normal, whereas the search for a second neoplasm was negative. The hypercalcemia initially responded to conventional treatment, but it reappeared two weeks later. Coincidentally, a high proportion of blast cells of T-cell origin at the cortical thymocyte stage were observed in the patient's peripheral blood and bone marrow, and she died shortly afterwards.

Extracellular calcium-sensing receptor expression and its potential role in regulating parathyroid hormone-related peptide secretion in human breast cancer cell lines

Metastasis of breast cancer to bone occurs with advanced disease and produces substantial morbidity. Secretion of PTH-related peptide (PTHrP) from breast cancer cells is thought to play a key role in osteolytic metastases and is increased by transforming growth factor-beta (TGFbeta), which is released from resorbed bone. Elevated extracellular calcium (Ca2+(o)) also stimulates PTHrP secretion from various normal and malignant cells, an action that could potentially be mediated by the Ca2+(o)-sensing receptor (CaR) originally cloned from the parathyroid gland. Indeed, we previously showed that both normal breast ductal epithelial cells and primary breast cancers express the CaR. In this study we investigated whether the MCF-7 and MDA-MB-231 human breast cancer cell lines express the CaR and whether CaR agonists modulate PTHrP secretion. Northern blot analysis and RT-PCR revealed bona fide CaR transcripts, and immunocytochemistry and Western analysis with a specific anti-CaR antiserum demonstrated CaR protein expression in both breast cancer cell lines. Furthermore, elevated Ca2+(o) and the polycationic CaR agonists, neomycin and spermine, stimulated PTHrP secretion dose dependently, with maximal, 2.1- to 2.3-fold stimulation. In addition, pretreatment of MDA-MB-231 cells overnight with TGFbeta1 (0.2, 1, or 5 ng/ml) augmented both basal and high Ca2+-stimulated PTHrP secretion. Thus, in PTHrP-secreting breast cancers metastatic to bone, the CaR could potentially participate in a vicious cycle in which PTHrP-induced bone resorption raises the levels of Ca2+(o) and TGFbeta within the bony microenvironment, which then act in concert to evoke further PTHrP release and worsening osteolysis.

Assessment of cellular expression of parathyroid hormone-related protein mRNA and protein in multiple myeloma

The capacity of multiple myeloma cells to generate parathyroid hormone-related protein (PTHrP) has been examined by in situ assessment of PTHrP mRNA and PTHrP protein in myeloma cells of patients in whom the disease was associated with the development of hypercalcaemia. The presence of PTHrP mRNA was evaluated by in situ hybridization using an antisense riboprobe, and PTHrP by immunohistochemistry using a monoclonal antibody, in archival bone marrow trephine specimens from 17 patients. PTHrP mRNA was detected in myeloma cells in 16 of the 17 patients, indicating a high frequency of PTHrP gene expression in myeloma cells in these subjects. PTHrP protein was, on the other hand, detected in the myeloma cells of only five of these patients. The impact of the mercury-based fixation and decalcification procedure used for processing the bone marrow trephine specimens was assessed to determine the influence of this process on the outcome of the immunohistochemical assay for PTHrP. It was shown that this preparative procedure resulted in a marked reduction of immunohistochemically detectable PTHrP, which provides a possible explanation for the lower frequency of positivity for PTHrP in myeloma cells in the bone marrow specimens. The present findings are consistent with the view that PTHrP can be generated in myeloma cells in vivo, and could contribute to osteolysis and hypercalcaemia, as in patients with cancer.

Expression and regulation of parathyroid hormone-related peptide in normal and malignant melanocytes

We examined parathyroid hormone-related peptide (PTHrP) production and regulation in both normal human melanocytes and in a human amelanotic melanoma cell line (A375). Northern blot and immunocytochemical analysis demonstrated that both cultured A375 cells and normal human melanocytes express PTHrP, but A375 cells expressed much higher levels of the peptide. PTHrP secretory rate increased at least 10-fold after treatment with 10% fetal bovine serum (100.2 +/- 2.8 pmol/10(6) cells vs. basal <15 pmol/10(6) cells) in proliferating A375 cells but only twofold in confluent cells. Treatment of A375 cells with increasing concentrations of 1, 25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] or its low-calcemic analog EB-1089 revealed that EB-1089 was 10-fold more potent than 1, 25-(OH)(2)D(3) on inhibition of both cell proliferation and PTHrP expression. Furthermore, inoculation of A375 cells into the mammary fat pad of female severe combined immunodeficiency mice resulted in the development of hypercalcemia and elevated concentrations of plasma immunoreactive PTHrP in the absence of detectable skeletal metastases. Our study, therefore, demonstrates a stepwise increase in PTHrP expression when cells progress from normal to malignant phenotype and suggests that EB-1089 should be further evaluated as a therapeutic agent in human melanoma.

Paraneoplastic rheumatic syndromes

Paraneoplastic rheumatic syndromes are challenging from both a clinical and research standpoint. Progress over the past decade has provided clarification of clinical syndromes. At the same time, our increasing ability to define and quantitate mediators of inflammation is shedding new light on pathogenesis. In turn, this understanding may answer questions regarding more common rheumatic diseases.

Extracellular calcium-sensing receptor (CaR) expression and its potential role in parathyroid hormone-related peptide (PTHrP) secretion in the H-500 rat Leydig cell model of humoral hypercalcemia of malignancy

Humoral hypercalcemia of malignancy (HHM) occurs when secretion of parathyroid hormone-related peptide (PTHrP) by cancer cells causes hypercalcemia in the absence of skeletal metastases. High extracellular calcium (Ca(2+)(o)) increases secretion of PTH-like bioactivity by rat H-500 leydig cells, a transplantable model of HHM, an action potentially mediated by the Ca(2+)(o)-sensing receptor (CaR). In this study we investigated whether H-500 cells express the CaR and, if so, whether CaR agonists modulate PTHrP secretion. Northern blot analysis and RT-PCR revealed bona fide CaR transcript(s), and immunocytochemistry and Western analysis with a specific anti-CaR antiserum demonstrated CaR protein expression in H-500 cells. Furthermore, high Ca(2+)(o) and neomycin stimulated PTHrP secretion dose-dependently with maximal 2.7- and 3.3-fold increases at 5 mM Ca(2+)(o) and 300 microM neomycin, respectively. Thus in HHM caused by H-500 cells, the CaR could participate in a vicious cycle whereby PTHrP-induced increases in Ca(2+)(o) further stimulate PTHrP release and exacerbate hypercalcemia.

Parathyroid hormone may be a cancer promoter - an explanation for the decrease in cancer risk associated with ultraviolet light, calcium, and vitamin D

Epidemiological studies reporting an inverse association between sunlight exposure and risk for cancers of the breast, colon, and prostate, have not yet been explained. Since ultraviolet (UV) light promotes dermal vitamin D generation, studies suggesting that dietary calcium and vitamin D may likewise have cancer-preventive activity are potentially of relevance. UV light, calcium, and vitamin D have the common property of suppressing parathyroid hormone (PTH) production; these considerations raise the possibility that PTH may have promotional activity for certain cancers. PTH might function indirectly in this regard, by increasing hepatic production of the progression growth factor IGF-I, a likely cancer promoter. A more direct role is suggested by recent evidence that many cancers express receptors for PTH/PTH-related protein; these receptors mediate co-mitogenic and/or pro-invasive signals in some cancers. High risk for previous or concurrent neoplasms has been reported in patients with parathyroid adenomas. In light of the increase in cancer risk associated with hypertension, it is notable that PTH levels are typically increased in salt-sensitive hypertensives. Prospective case-control studies examining serum PTH in relation to subsequent cancer risk appear warranted.

Parathyroid hormone-related protein, parathyroid hormone, and vitamin D in hypercalcemia of malignancy

The pathogenesis of cancer-associated hypercalcemia is not yet completely understood. In the majority of cancer patients, hypercalcemia appears to be a consequence of the tumor production of parathyroid hormone (PTH)-related protein (PTHrP). However, patients with humoral hypercalcemia of malignancy, in contrast to those with primary hyperparathyroidism, have an uncoupled bone turnover, and they usually have low circulating levels of 1.25(OH)2D3. We performed a case-control study to assess the relationship of plasma PTHrP, PTH and 1.25(OH)2D3 with hypercalcemia in cancer patients with a variety of tumors. Sixty of these patients had hypercalcemia, and 45 were normocalcemic. We measured PTHrP and PTH by immunoradiometric assay (Nichols), and 1.25(OH)2D3 by radioreceptor assay (Nichols), in plasma in both groups of cancer patients. Using a logistic regression analysis, we found that the higher PTHrP in plasma, the higher association with hypercalcemia occurred in these patients. In addition, the decreased plasma levels of PTH and 1.25(OH)2D3 in the majority of cancer patients were found to be significantly associated with hypercalcemia. Our results indicate that the combined determination of PTH, PTHrP and 1.25(OH)2D3 in plasma represents a more comprehensive approach to the investigation of hypercalcemia in cancer patients. Our data also support the role of PTHrP as a humoral factor responsible for hypercalcemia in these patients.

Primary multifocal lymphoma of bone presenting as hypercalcemic crisis: report of a rare manifestation of extranodal lymphoma

Primary non-Hodgkin's lymphoma of bone is uncommon and usually manifests clinically as localized bone pain. Here we report a woman who presented with hypercalcemic crisis and extensive investigation revealed a primary multifocal lymphoma of bone. The course of the disease was very aggressive and despite intensive supportive care and urgent chemotherapy the patient died within 1 month. Since her blood PTH and calcitriol levels were suppressed and her parathyroid-hormone-related peptide (PTHrp) was mildly elevated, we believe that release of cytokines combined with PTHrp, as well as extensive osteolytic lesions, were the causes of the hypercalcemia. This is an unusual presenting symptom of lymphomas and to the best of our knowledge severe symptomatic hypercalcemia and crisis has never been reported in primary lymphoma of bone before.

Significance of parathyroid hormone-related protein as a factor stimulating bone resorption and causing hypercalcemia in myeloma

Elevated levels of parathyroid hormone-related protein (PTHrP) in hypercalcemic myeloma patients were demonstrated in recent reports, suggesting that PTHrP behaves as a humoral mediator of hypercalcemia in myeloma. Herein we describe a hypercalcemic myeloma patient with a high serum PTHrP level. Moreover, the PTHrP level in the supernatant of bone marrow aspirates was about two-fold of that in serum. Reverve transcriptase-polymerase chain reaction analysis showed PTHrP m-RNA in bone marrow containing myeloma cells. After chemotherapy, the concentrations of calcium and PTHrP decreased and PTHrP mRNA in bone marrow became undetectable. We conclude that PTHrP released by myeloma cells acted as the main bone resorption stimulating factor in this case.

Parathyroid hormone-related protein mRNA and protein expression in multiple myeloma: a case report

Multiple myeloma frequently leads to complications, such as osteolytic lesions, hypercalcemia, and pathological fractures. Increased bone resorption in myeloma is due to osteoclast activation. The nature of the osteoclast activator(s) remains unclear. We describe a case of multiple myeloma with marked hypercalcemia and skeletal complications that progressed rapidly despite chemotherapy. The patient had marked hypercalcemia at diagnosis (4.5 mmol/l), and elevated parathyroid hormone-related protein (PTHrP) levels were found in plasma. Analysis of the bone marrow trephine biopsy showed PTHrP gene transcription and protein in myeloma cells. These results provide strong evidence for the production of significant amounts of PTHrP by human myeloma cells. PTHrP has been measured as elevated in the plasma of patients with myeloma and might be an important contributor to the skeletal complications in this disease.

Parathyroid hormone-related protein in hypercalcemia associated with hematological malignancy

Hypercalcemia is an important complication in multiple myeloma as well as T-cell leukemia/lymphoma, and is moderately common in high and intermediate grade non-Hodgkin's lymphoma. The underlying mechanism has been unclear because the neoplastic cells are usually present in the bone marrow, where they are in a position to produce short range effects on bone resorption which are difficult to identify. This contrasts with the situation in hypercalcemia associated with non-metastatic carcinoma, where it has been clearly demonstrated that the most common cause is release from the tumor of a humoral mediator, Parathyroid Hormone-related Protein (PTHrP). Roles have been advocated in multiple myeloma for release of a number of other cytokines with osteolytic capacity on the basis of their enhancement of osteolytic activity in cultured fetal rat bone, although a causal relationship in patients has not been established. PTHrP has more recently been implicated in the genesis of hypercalcemia in patients with hematological malignancies by the demonstration in a proportion of cases of increased circulating levels of PTHrP, comparable to those in hypercalcemia due to cancer. Immunohistochemical studies indicate neoplastic hemopoietic cells can contain PTHrP, and thus have the capacity to act in a paracrine manner to enhance local bone resorption and contribute to the development of hypercalcemia.

Value of assessing parathyroid hormone-like activity in a case of extreme hypercalcaemia

A previously well 70 year old woman was admitted to hospital following a three day history of vomiting and confusion. Her serum calcium was 6.58 mmol/l, phosphate 1.09 mmol/l, and alkaline phosphatase 91 iu/l. The mechanism of this hypercalcaemia was not obvious as there was no evidence of a primary malignancy, lymphadenopathy or hepatosplenomegaly. The calculation of indices of urinary excretion of calcium and phosphate suggested the presence of excessive parathyroid hormone (PTH) activity as the mechanism of hypercalcaemia. Plasma intact PTH, 25-hydroxycholecalciferol, and 1,25-dihydroxycholecalciferol were not raised suggesting the presence of PTH related peptide (rP). This led to a systematic search for a malignancy, which revealed the presence of a high grade B cell non-Hodgkin's lymphoma confined to the bone marrow. Plasma PTH-rP was subsequently shown to be raised confirming the interpretation of the initial urinary and calcium excretion indices. This case highlights the value of standard laboratory measurements such as urinary calcium and phosphate excretion in cases of hypercalcaemia of obscure aetiology, which can complement measurements of PTH and other calcitropic hormones.

Biopsy specimen appearances of ischaemic gastritis in splanchnic arterial insufficiency

A 74 year old man presented with a one month history of epigastric discomfort, anorexia, weight loss, and postprandial vomiting. The diagnosis of ischaemia was made on endoscopic biopsies from the stomach and duodenum. He was too ill for major vascular surgery and died eight days after admission. Postmortem examination confirmed the diagnosis of splanchnic arterial insufficiency caused by atheroma and thrombosis. Ischaemic gastritis is rare but could easily be missed in unrepresentative biopsy specimens. Prompt diagnosis with revascularisation surgery is the only hope for long term survival.

Sample dilution to resolve mistaken identification of haemoglobin D as haemoglobin E using the variant automated system

High performance liquid chromatography (HPLC) is increasingly being used to estimate variant haemoglobins. A case of haemoglobin S/D (HbS/D) is presented, which was misdiagnosed as haemoglobin S/E (HbS/E) by HPLC. The patient was a 22 year old woman with sickle cell anaemia. Subsequent haemodilution by blood transfusion clearly elucidated the haemoglobin D peak on HPLC. Sample dilution experiments, using the pretransfusion sample, were done resulting in correct elution of the peak in the D window. Troubleshooting in similar problematic haemoglobin variant peaks seen on HPLC can be done by sample dilution.