Mutational and biochemical findings in adults with persistent hypophosphatasemia.

A majority of adults with persistently low serum alkaline phosphatase values carry a pathogenic or likely pathogenic variant in the ALPL gene and also have elevated alkaline phosphatase substrate values in serum and urine. These adults may fall within the spectrum of the adult form of hypophosphatasia. INTRODUCTION: The primary objective of this study was to determine what proportion of adults with persistently low serum alkaline phosphatase values (hypophosphatasemia) harbor mutations in the ALPL gene or have elevated alkaline phosphatase (ALP) substrates. Some adults with persistent hypophosphatasemia share clinical and radiographic features with the adult form of hypophosphatasia (HPP). In HPP, ALPL mutations result in persistent hypophosphatasemia and ALP substrate accumulation in plasma (pyridoxal-5-phosphate (PLP)) and urine (phosphoethanolamine (PEA)). METHODS: Biochemical analyses, including serum ALP activity, bone-specific ALP, plasma PLP, and urine PEA, were performed in adults with persistent hypophosphatasemia. Mutational analyses were performed using PCR and Sanger sequencing methods. Gene variants were classified as pathogenic (P), likely pathogenic (LP), variants of uncertain significance (VUS), likely benign (LB), and benign (B). P and LP variants were further grouped as "Positive ALPL variants" and LB and B grouped as "Negative ALPL variants." RESULTS: Fifty subjects completed all mutational and biochemical analyses. Sixteen percent carried only Negative ALPL variants. Of the remaining 42 subjects, 67% were heterozygous for a P variant, 19% for an LP variant, and 14% for a VUS. Biochemical results were highly inter-correlated and consistent with the expected inverse relationship between ALP and its substrates. Subjects harboring Positive ALPL variants showed lower ALP and BSAP and higher PLP and PEA values compared with subjects harboring only Negative ALPL variants. Approximately half of all subjects harboring Positive ALPL variants or ALPL VUS showed elevations in plasma PLP, and three quarters showed elevations in urine PEA. CONCLUSION: Adults with persistent hypophosphatasemia frequently harbor ALPL mutations and have elevated ALP substrates. These adults may fall within the spectrum of the adult form of hypophosphatasia. Clinicians should take note of persistent hypophosphatasemia in their patients and be cautious in prescribing bisphosphonates when present.

Clinician approach to diagnosis of stress fractures including bisphosphonate-associated fractures.

Stress fractures are repetitive strain injuries that occur in normal bones and in abnormal bones. Stress fractures share many features in common but differences depend on the status of the underlying bone. This review article for clinicians addresses aspects about stress fractures with particular respect to fatigue fractures, Looser zones of osteomalacia, atypical Looser zones, atypical femoral fractures associated with bisphosphonate therapy and stress fractures in Paget's disease of bone.

Acute hypophosphatasemia.

UNLABELLED: The temporal evolution of a low serum alkaline phosphatase value may relate to its cause. Precipitous lowering of serum alkaline phosphatase below the lower range of normal is uncommon and may indicate severe physiologic stress and increased short-term mortality. INTRODUCTION: The differential diagnosis of a low serum alkaline phosphatase (ALP) value (hypophosphatasemia) is wide ranging, anecdotal, and unfamiliar. The temporal evolution of hypophosphatasemia may relate to its cause. The purpose of this study is to report conditions and circumstances associated with precipitous lowering of serum ALP below the lower range of normal. METHODS: Marshfield Clinic IRB approved use of their electronic medical record to search for subjects with at least two serum ALP values ≤ 40 U/L (normal 40-125 U/L). When the temporal evolution of the qualifying ALP values indicated a precipitous lowering from usually normal serum ALP values, the subject was deemed to have acute hypophosphatasemia. Thirty years of laboratory data and 10 years of clinical narrative were analyzed. Associated diagnoses, clinical circumstances, and short-term mortality were recorded. RESULTS: A total of 458,767 subjects had 2,584,051 serum ALP values, and 5,190 (1.1 %) subjects had at least two serum values ≤ 40 U/L. A detailed review of 1,276 subjects selected on the basis of their lowest ALP value and age identified 190 subjects with acute hypophosphatasemia. Acute hypophosphatasemia was recorded during periods of major trauma/surgery, multisystem failure, acute anemia, blood product transfusions (often massive), apheresis, hypomagnesemia, and acute caloric restriction. Twenty-eight subjects (15 %) died within 35 days of their nadir serum ALP. CONCLUSION: Acute hypophosphatasemia is associated with profound illness or physiologic stress and followed by increased short-term mortality. The temporal evolution of hypophosphatasemia may relate to its cause.

The effect of teriparatide compared with risedronate on reduction of back pain in postmenopausal women with osteoporotic vertebral fractures.

UNLABELLED: The effect of teriparatide and risedronate on back pain was tested, and there was no difference in the proportion of patients experiencing a reduction in back pain between groups after 6 or 18 months. Patients receiving teriparatide had greater increases in bone mineral density and had fewer vertebral fractures. INTRODUCTION: This study aimed to understand the effect of teriparatide in reducing back pain in patients with prevalent back pain and vertebral fracture compared to risedronate. METHODS: In an 18-month randomized, double-blind, double-dummy trial, we investigated the effects of teriparatide (20 µg/day) vs. risedronate (35 mg/week) in postmenopausal women with back pain likely due to vertebral fracture. The primary objective was to compare the proportion of subjects reporting ≥30% reduction in worst back pain severity from baseline to 6 months as assessed by a numeric rating scale in each treatment group. Pre-specified secondary and exploratory outcomes included assessments of average and worst back pain at additional time points, disability and quality of life, bone mineral density, incidence of fractures, and safety. RESULTS: At 6 months, 59% of teriparatide and 57% of risedronate patients reported ≥30% reduction in worst back pain and there were no differences between groups in the proportion of patients experiencing reduction in worst or average back pain at any time point, disability, or quality of life. There was a greater increase from baseline in bone mineral density at the lumbar spine (p = 0.001) and femoral neck (p = 0.02) with teriparatide compared to risedronate and a lower incidence of vertebral fractures at 18 months (4% teriparatide and 9% risedronate; p = 0.01). Vertebral fractures were less severe (p = 0.04) in the teriparatide group. There was no difference in the overall incidence of adverse events. CONCLUSIONS: Although there were no differences in back pain-related endpoints, patients receiving teriparatide had greater skeletal benefit than those receiving risedronate.

The utility of BMD Z-score diagnostic thresholds for secondary causes of osteoporosis.

UNLABELLED: This very large dual X-ray absorptiometry (DXA) cohort confirmed a significant, inverse relationship between bone mineral density (BMD) Z-scores and the presence of secondary causes of osteoporosis but receiver operating characteristic (ROC) curves indicate that Z-score diagnostic thresholds (such as -2.0) discriminate poorly between the presence and absence of secondary causes of osteoporosis. INTRODUCTION: BMD Z-score diagnostic thresholds have been proposed to detect secondary causes of osteoporosis. To determine the sensitivity and diagnostic utility of such thresholds, we analyzed comprehensive BMD and personal health information data from a large, multispecialty group practice. METHODS: Adult subjects were assigned their lowest axial BMD Z-score and ICD-9 diagnosis codes for secondary causes of osteoporosis when cited at least twice in their electronic medical record. Multiple logistic regression was used to model the prevalence of matching ICD-9 codes as a function of Z-score. ROC curves were used to investigate various Z-score cut points for sensitivity and specificity. RESULTS: Eighteen thousand six hundred seventy-four subjects were analyzed. Secondary causes of osteoporosis were identified in 31% of men and 16% of women. The frequency of secondary causes varied with age and between genders and varied inversely with Z-score. No inflection point was observed in this relationship to suggest a useful clinical decision threshold. The difference in mean Z-score of those with and without a secondary cause of osteoporosis was biologically slight (±0.3). Low Z-score diagnostic thresholds were insensitive to the presence of secondary causes of osteoporosis and provided relatively poor predictive value. CONCLUSIONS: This DXA cohort confirmed a significant inverse relationship between Z-score and the presence of secondary causes of osteoporosis but diagnostic Z-score thresholds discriminate poorly between the presence and absence of secondary causes of osteoporosis. If only patients with very low Z-scores are evaluated for secondary causes of osteoporosis the diagnostic specificity may be high but most cases will be missed.

Integrated anti-remodeling and anabolic therapy for the osteoporosis of Hajdu-Cheney syndrome.

Hajdu-Cheney syndrome (MIM 102500) is a rare skeletal dysplasia marked by severe generalized osteoporosis and focal bone loss (acro-osteolysis). Osteoporosis treatment outcome has been reported only once previously. Reported herein is the biochemical and densitometric response to integrated anti-remodeling and anabolic therapy in a woman with Hajdu-Cheney syndrome. Results suggest dissociation of bone formation from bone resorption resulting in dramatic increases in bone mineral density without clinical evidence of activated osteoporosis.

Analysis of T cell and B cell function in Peyer's patch and lamina propria of New Zealand Black and DBA/2 mice.

We have analyzed gastrointestinal immune function in both DBA/2 and spontaneously autoimmune New Zealand Black (NZB) mice. We have studied both in vitro proliferation and differentiation of Peyer's patch cells and have measured immunoglobulin (Ig) secretion by cultured jejunal segments. Peyer's patch B cells and T cells from both DBA/2 and NZB mice showed similar proliferative responses to Con A and lipopolysaccharide (LPS), respectively. Unlike NZB splenic B cells, isolated Peyer's patch B cells from NZB mice did not spontaneously secrete Ig of any isotype. Seven-day cultures of equal numbers of Peyer's patch T cells and B cells resulted in similar patterns of secretion of IgA, IgG, and IgM in both strains. The addition of Con A to cultures of DBA/2 Peyer's patch cells consistently resulted in a onefold to threefold increase in IgA secretion after 7 days. Con A stimulation of NZB Peyer's patch cells did not produce any increment in IgA secretion. LPS stimulation of Peyer's patch cells from either strain resulted in a similar increase in IgG secretion with little effect on IgA secretion. The in vivo correlate of this finding was seen in the IgA to IgG ratio of Ig secreted by cultured jejunal fragments. In DBA/2 mice the rates of IgA/IgG varied from 2.36 to 4.85, whereas in NZB mice the ratio never exceeded 0.5. These experiments show that defects on the T cell compartment of NZB mice encompass gut-associated lymphoid tissue. The possible relationship of these findings and previously observed defects in oral tolerance is discussed.