Analysis of Bone Mineral Density, Biochemical Bone Turnover Markers and Serum Tryptase Levels in Patients with Systemic Mastocytosis (SM).
Authors: Yavuz Akif S. , Alpay Nilüfer , Dogan Öner , Büyükbabani Nesimi , Baykal Can , Sindel Dilsad , Pekçelen Yüksel , Tanakol Refik 
Published: October 2019

Osteoporosis, osteosclerosis and lytic lesions, have been observed in patients with SM possibly reflecting different amounts of infiltrating mast cells and variation in the active substances they secrete. SM patients may be prone to pathological fractures. In a former study using dual energy X-ray absorptiometry (DXA), it was reported that SM patients with more severe disease had significantly higher bone density at the L1–L4 spine and femoral neck then those patients with less severe disease. We therefore investigated the value of quantitative ultrasound QUS of the calcaneus expressed as the stiffness index in the assessment of BMD in SM patients, as well as BMD of lumbar spine (L1–L4), femoral neck and distal radius using DXA and biochemical markers of bone turnover, plasma tryptase levels and their correlation with the clinical features. Fourteen adult patients (4 females, 10 males, median age 37, and range 23–64) with mastocytosis were included in this study. Overall, nine out of 14 patients had T scores at L1–L4 spine, femoral neck, and distal radius or as calcaneus stiffness less than −1 at least at one site reflecting osteopenia. Three out of 14 patients had T scores showing osteoporosis (T score<-2.5) (Table 1). There was a significant negative correlation between tryptase levels and distal radius T scores and a significant positive correlation between tryptase levels and disease severity as well as between disease severity and pyridinoline, a marker of osteoclastic activity. The distal radius T scores showed a negative correlation with disease severity (p<0.05 by Spearman’s test). DXA is not an appropriate technique to assess osteopenia in SM patients because of osteosclerosis, which occurs more frequently in patients with severe disease. However, this study supports the value of DXA, assessed at distal radius, for showing osteopenia in patients with mastocytosis. To assess the reliability of QUS of the calcaneus in SM patients more cases are needed. The osteoclastic marker pyridinoline is helpful in patients with severe disease activity and sclerotic bone lesions to show bone demineralization.

Table 1 L1-L4 spine Femoral neck Distal radius Diagnostic category Tscore<-1 (n) Tscore<-2.5(n) Tscore<-1 (n) Tscore<-2.5(n) Tscore<-1 (n) Tscore<-2.5(n) Calcaneus stiffnessTscore<-1(n) CM: Cutaneous mastocytosis, ISM: Indolent systemic mastocytosis, SSM: Smoldering systemic mastocytosis, ASM: Aggressive systemic mastocytosis, MCL: Mast cell leukemia, ND: not done All (n=14) 6 2 1 0 9 2 7 CM (n=4) 0 0 0 0 1 0 1 ISM (n=6) 5 2 1 0 5 1 5 SSM (n=2) 1 0 0 0 2 1 1 ASM (n=1) 0 0 0 0 0 0 0 MCL (n=1) 0 0 0 0 1 0 ND Table 2 Diagnostic category Disease severity Osteocalcin (3.1–13.7 ng/ml) Bone alkaline phosphatase (Females: 11.6–29.6 U/L, males: 15–41.3 U/L) Deoxypyridinoline (Females: 6–13.5 and males: 5–11 pmol/μmol creatinine) Pyridinoline (Females: 25–63 and males: 20–52 pmol/μmol creatinine) Tryptase levels(<13.5 μg/L) Lytic lesions/ Sclerotic lesions All (n=14) - 9±7 51±40 9±3 59±43 89±71 6/3 CM (n=4) 1 8±6 37±16 6±1 19±7 5±2 0/0 ISM (n=6) 2 6±4 40±11 9±4 51±18 109±55 2/0 SSM (n=2) 3 19±12 42±10 12±0 86±3 144±38 2/1 ASM (n=1) 4 2 48 6 114 80 1/1 MCL (n=1) 5 9 185 11 161 200 1/1