Osteoporosis and fractures in mastocytosis

Osteosclerosis is an elevation in bone density.  Osteoporosis is a progressive decrease in bone density that increases the risk of fracture.  Both conditions of the bone are associated with mastocytosis. 

Several studies have been done on the topic of bone involvement in mastocytosis.  On average, 70% of SM patients showed bone changes on x-ray; 28% had osteoporosis; 16% had osteoporosis with facture; 19% had osteosclerosis; and 10% had a mixed pattern of bone involvement. 

In one study, 83 of 154 patients experienced 235 fractures during their lifetime.  43% of patients under 50 years of age and 61% of patients over 50 had at least one fracture.  140 fractures in 57 patients occurred because of “low-energy trauma,” meaning the bone broke easily.  87 of these fractures affected the vertebrae, while 53 did not.  27% of patients had 1 or more vertebral fractures, 21% had non-vertebral, osteoporotic fractures. 

Osteoporotic fractures were found in 35% of men and 6% of women under 50, 62% of men and 40% of women over 50.  High energy trauma fractures were reported by 32% of patients.  Unlike in the general population, among mastocytosis patients, men are heavily affected.  The risk of osteoporotic fractures increased with age.  Increased age, male gender and high n-methylhistamine levels were found to correlate with osteoporosis in mast cell disease.  Additionally, levels of c-telopeptide and osteoprotegerin were higher in patients with advanced disease. 

Mast cells are known to be involved in bone loss.  They release inflammatory molecules  IL-1, IL-6 and TNF-a, which regulate bone resorption.  Markers that indicate bone resorption (C-telopeptide, deoxypyridinoline), bone formation (bone-specific alk phos) and bone remodeling (osteoprotegerin) are much higher in SM than in control population.

According to the WHO criteria, pathological fracture of a bone is considered a C-finding.  This means that a break in a bone weakened by mastocytosis is diagnostic for aggressive systemic mastocytosis.  However, a fracture due to osteoporosis is NOT a C-finding. 

SM patients should take preventative measures to lessen their risk of osteoporosis, such as daily exercise and adequate calcium and vitamin D intake.  It is not known if use of antihistamines or cromolyn lessens the risk of pathological fracture. Bisphosphonate treatment is effective in SM patients with osteoporosis.