The cause of his osteoporosis was only skin deep

A 38-year-old, muscular, seemingly healthy man presented with compression fractures of T11 and L1 sustained while carrying two crates of beer from the cellar to the bar where he was working. He had been doing this for years without difficulty. Bone density was low at all measurement sites (T scores, –2.1 to –2.7).

The initial history was unremarkable, including the absence of any prior history of fracture or family history of fracture or osteoporosis. A very comprehensive laboratory work-up uncovered no abnormality.

When I examined his back the rash was obvious. He reported that he had had this for some time and he had become used to the itching. Dermatographia was readily apparent and the presumptive diagnosis of mastocytosis was confirmed by skin biopsy and elevated urine histamine. Bone marrow biopsy was not performed because his hematology profile was normal and the hematologist felt that no further useful information that would affect therapy would be obtained. Therapy was initiated with an H-1 blocker and more specific therapy for osteoporosis was delayed for a few months until the rash improved.

I have since adopted the habit of checking for dermatographia in patients where the etiology of the osteoporosis is not immediately clear. A positive clinical result is not uncommon but I have yet to encounter a patient with an elevated urine histamine in the absence of a rash suggestive of urticaria pigmentosa.

Systemic mastocytosis is an uncommon etiology for accelerated bone loss and osteoporosis and not all cases present with clinical clues as did this patient. There have been a few case studies reported where the diagnosis was only established when a bone biopsy was obtained to seek clues to the pathogenesis that had escaped diagnosis despite a complete history, physical exam and laboratory work-up. With currently available laboratory studies related to bone and mineral metabolism the use of invasive bone biopsy for purposes other than research has appropriately decreased substantially.

The list of etiologies for osteoporosis keeps growing. Treating a recognized cause (eg, celiac disease, hypogonadism) should always be initiated. The harder question to answer is if and when more specific therapy for osteoporosis should be implemented.