To the Editor: A 51-year-old man with a history of hypertension, depression, and anxiety presented with low back pain at rest that increased with movement. The pain began when the patient was coughing during a mild cold that had already been remitted at the time of the examination. The patient had no recent history of trauma.

The physical examination showed localized tenderness to palpation over the lumbosacral spine. Conservative treatment was initiated with nonsteroidal anti-inflammatory drugs. When the pain persisted after six weeks, magnetic resonance imaging of the lumbosacral spine was performed that showed loss of height in the L3 vertebral body suggesting a fracture or intravertebral disc herniation.

Laboratory test results showed normal red and white blood cell and platelet counts, liver function, renal function, electrolytes, C-reactive protein, 25-hydroxyvitamin D, sedimentation rate, and thyroid and parathyroid function. Urine calcium concentration was high at 24.6 (normal range = 6.8 to 21.3). Bone densitometry showed a lumbar bone mass of 0.662 (traumatic disc extrusion = 4.5) and a femoral neck bone mass of 0.595 (traumatic disc extrusion = 3.6). The patient was diagnosed with lumbar and femoral neck osteoporosis with L3 vertebral fracture and hypercalciuria. Treatment was initiated with alendronate/cholecalciferol (Fosamax Plus D), with repeat densitometry in two years showing a clear improvement in bone mass. During this time, the patient reported worsening anxiety and depression, asthenia, anhedonia, and recurrent presyncope episodes. The patient also developed small hyperpigmented, pruritic papules, most predominantly above the waist, that became more noticeable after exercise or abrupt temperature changes.

Elements of the patient′s clinical history suggested systemic mastocytosis; therefore, serum tryptase levels were measured with a positive result of 23.6 ng per dL (normal range = less than 20 ng per mL). A hematologist performed a bone biopsy and confirmed the diagnosis. Disodium cromoglycate was added to the patient's regimen of alendronate/cholecalciferol, resulting in the progressive improvement of symptoms.

The diagnosis of systemic mastocytosis requires a high index of clinical suspicion because of the nonspecific nature of its symptoms. In this case, an osteoporotic vertebral fracture in an atypically young patient, in addition to psychiatric and dermatologic symptoms, provided important clues to the eventual diagnosis.