'Sink or swim': an evaluation of the clinical characteristics of individuals with high bone mass

SUMMARY

High bone mineral density on routine dual energy X-ray absorptiometry (DXA) may indicate an underlying skeletal dysplasia. Two hundred fifty-eight individuals with unexplained high bone mass (HBM), 236 relatives (41% with HBM) and 58 spouses were studied. Cases could not float, had mandible enlargement, extra bone, broad frames, larger shoe sizes and increased body mass index (BMI). HBM cases may harbour an underlying genetic disorder.

INTRODUCTION

High bone mineral density is a sporadic incidental finding on routine DXA scanning of apparently asymptomatic individuals. Such individuals may have an underlying skeletal dysplasia, as seen in LRP5 mutations. We aimed to characterize unexplained HBM and determine the potential for an underlying skeletal dysplasia.

METHODS

Two hundred fifty-eight individuals with unexplained HBM (defined as L1 Z-score ≥ +3.2 plus total hip Z-score ≥ +1.2, or total hip Z-score ≥ +3.2) were recruited from 15 UK centres, by screening 335,115 DXA scans. Unexplained HBM affected 0.181% of DXA scans. Next 236 relatives were recruited of whom 94 (41%) had HBM (defined as L1 Z-score + total hip Z-score ≥ +3.2). Fifty-eight spouses were also recruited together with the unaffected relatives as controls. Phenotypes of cases and controls, obtained from clinical assessment, were compared using random-effects linear and logistic regression models, clustered by family, adjusted for confounders, including age and sex.

RESULTS

Individuals with unexplained HBM had an excess of sinking when swimming (7.11 [3.65, 13.84], p < 0.001; adjusted odds ratio with 95% confidence interval shown), mandible enlargement (4.16 [2.34, 7.39], p < 0.001), extra bone at tendon/ligament insertions (2.07 [1.13, 3.78], p = 0.018) and broad frame (3.55 [2.12, 5.95], p < 0.001). HBM cases also had a larger shoe size (mean difference 0.4 [0.1, 0.7] UK sizes, p = 0.009) and increased BMI (mean difference 2.2 [1.3, 3.1] kg/m(2), p < 0.001).

CONCLUSION

Individuals with unexplained HBM have an excess of clinical characteristics associated with skeletal dysplasia and their relatives are commonly affected, suggesting many may harbour an underlying genetic disorder affecting bone mass.

Outcome of a cohort of 300 patients with systemic lupus erythematosus attending a dedicated clinic for over two decades

OBJECTIVE

To examine the mortality rate and causes of death in a cohort of 300 patients with systemic lupus erythematosus (SLE).

METHODS

A retrospective analysis was performed on all patients attending the SLE clinic between 1978 and 2000. Information was obtained on those patients lost to follow up. Cause of death was analysed and categorised as early (<5 years after diagnosis of SLE) and late (>5 years after diagnosis of SLE). Standardised mortality rates were obtained.

RESULTS

The patients were followed up for a median of 8.3 years. Seventy three (24%) patients were no longer followed up at the end of the study period, of whom 41 (14%) had died. Of the 32 patients lost to follow up, 14 were being actively followed up within the UK, 16 were followed up outside the UK, and two patients were untraceable. The most common cause of death was malignancy, which accounted for eight (20%) deaths, followed by infection and vascular disease, which accounted for seven (17%) deaths each.

CONCLUSIONS

Malignancy was the most common cause of death. Cause of death varied depending on disease duration. Forty per cent of early deaths were due to SLE related renal disease, whereas 23% of late deaths were due to vascular causes. Death due to infection occurred throughout the follow up period. There was a fourfold increased risk of death in our cohort of patients with SLE compared with the general population.

Comparison of renal disease severity and outcome in patients with primary antiphospholipid syndrome, antiphospholipid syndrome secondary to systemic lupus erythematosus (SLE) and SLE alone

OBJECTIVE

To ascertain the clinical presentation, histopathology and outcome of renal involvement in patients with primary antiphospholipid syndrome (PAPS), antiphospholipid syndrome secondary to systemic lupus erythematosus (SAPS) and systemic lupus erythematosus alone.

METHOD

A retrospective analysis was undertaken of 20 patients with PAPS, 25 patients with SAPS and 275 patients with systemic lupus erythematosus to ascertain the frequency and pattern of renal involvement.

RESULTS

Renal involvement was found most frequently in patients with SAPS, in whom it occurred in 68% of patients. Renal disease was equally common in patients with PAPS and systemic lupus erythematosus alone where it was seen in 30% of patients. Patients with systemic lupus erythematosus most frequently presented with nephrotic syndrome due to glomerulonephritis, whereas those with PAPS and SAPS were more likely to present with hypertension and reduced glomerular filtration rate. No patients with PAPS developed end-stage renal failure compared with 5.9% of patients with SAPS and 16.9% of patients with systemic lupus erythematosus alone; 23.5% of patients with SAPS died compared with 15.7% of patients with systemic lupus erythematosus alone and no patients with PAPS.

CONCLUSION

Renal involvement is a major feature of both PAPS and SAPS, where renal thrombosis frequently leads to reduced glomerular filtration rate and hypertension. One-third of patients with systemic lupus erythematosus alone develop glomerulonephritis leading to renal disease which most commonly presents with nephrotic syndrome. Patients with PAPS were less likely to develop end-stage renal failure or die during the follow-up period.