When the Bones Tell a Different Story: An Atypical Presentation of Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia has a wide range of clinical presentations, such as anemia, fatigue, and thrombocytopenia. However, one may find rare presentations like bone lytic lesions that mimic multiple myeloma.

Herein, we report a case of B-cell Acute Lymphoblastic Leukemia that first presented with osteolytic bone lesions with associated hypercalcemia. This unusual observation indicates that B cell disorders other than multiple myeloma may present with unusually significant bone resorption, which results in excessive osteoclastic resorption, lytic bone lesions, and recurrent hypercalcemia, with an overall disease picture clinically mimicking multiple myeloma. Large series have estimated the frequency of this phenomenon to be about 2 percent.

We report a 29-year-old male who is not known to have a medical illness and presented with chronic intermittent lower back pain. It responded minimally to rest and nonsteroidal painkillers, requiring multiple visits to the emergency department. There is no history of numbness or weakness in the lower limbs. Also, history is significant for weight loss of almost 7 kilograms. Initial workup, including routine labs, showed a hemoglobin level of 10.2 mg/dl and an MCV of 81.6. The iron panel was suggestive of anemia of chronic disease.

The adjusted calcium level was 2.65, the CRP level was 90 mg/l, and the LDH was 248. Interestingly, the sacroiliac and thoracolumbar spine X-rays reported a diffuse decrease in bone density with decreased lower thoracic and lumbar spine vertebral body height, mainly at the T8 level. Later, the HLAB27 returned negative. Magnetic Resonance (MRI) of the spine with contrast was done later on and showed heterogeneous bone marrow signal intensity with relative T1W1 hypointensity. Postcontrast images have demonstrated patchy enhancement of T11.

All findings suggest possible bone infiltrative disease (e.g., myeloma, lymphoma, leukemia, or metastasis). A peripheral smear showed a leucoerythroblastic picture with mild thrombocytopenia, and multiple myeloma workups returned unremarkable. Ultrasound of the abdomen and pan-computed tomography scan were generally unremarkable except for demonstrating diffuse lytic skeletal infiltration involving most axial skeletal bones, including the sternum, ribs, vertebral column, and pelvic bones. So, based on the above assessment, a bone marrow assessment was performed to explain the picture of anemia, mild hypercalcemia, and hypodense vertebral bone lesions. Pelvic bone marrow aspirate and biopsy were performed, which interestingly showed around 36% blast cells with an immunophenotype profile consistent with precursor B cells (ALL) with standard risk and negative minimal residual disease (MRD). As part of the initial leukemia workup, the fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan showed the same extensive lytic lesions throughout the axial skeleton. Urgent tumor lysis syndrome prophylactic measures and IV Dexamethasone were initiated, and chemotherapy protocol was planned. He was started on the BFM2009 protocol, followed by a total of 6 cycles of intrathecal methotrexate without significant complications. A follow-up evaluation via PET scan showed a complete response (Figure 6). A follow-up bone marrow biopsy showed 2% blast cells. Then, he was started on maintenance therapy of oral MTX and mercaptopurine with a folic acid supplement.

In conclusion, a lytic bone lesion is an unusual presentation of B-cell ALL, mimicking the picture of multiple myeloma. Hence, it should always be one of the differentials in a presentation of this nature. Further similar cases should be reported to study the behavior of such an unusual presentation of B-cell ALL.

No relevant conflicts of interest to declare.