An Elusive Case of Acute Lymphoblastic Leukemia Initially Presenting as Myelofibrosis

Introduction: Myelofibrosis is a rare bone marrow disorder that is characterized by abnormalities in hematopoiesis and the formation of fibrous tissue within the bone marrow. Pediatric myelofibrosis is a rare entity usually secondary to infections, metabolic disorders or hematologic malignancies. Acute lymphoblastic leukemia is the most common type of childhood cancer and is rarely associated with myelofibrosis. We report here a case of an 8-year-old male with an unusual presentation of pancytopenia, severe infection, acute myelofibrosis and the later development of pre-B-cell acute lymphoblastic leukemia.

Case Description: An 8-year-old male was admitted with complaints of 5 days of intermittent fevers, fatigue, and decreased oral intake. Physical exam was notable for tenderness in his bilateral calves with difficulty ambulating. The patient was found to have pancytopenia. A bone marrow aspiration and biopsy revealed a decreased cell population with marrow reticulin fibrosis and no evidence of acute neoplasia. As the patient continued to have fevers, a CT scan of the abdomen/pelvis was performed and revealed an abscess in the right obturator muscle and left gluteal muscle. The left gluteal abscess was drained and found to grow Staphylococcus Aureus. He was treated with IV antibiotics and subsequently his fevers, pain, and pancytopenia resolved.

The patient was discharged to follow-up in the outpatient hematology clinic and remained with stable counts for 3 months until developing fevers and pancytopenia once again. A repeat bone marrow biopsy and aspiration showed resolved fibrosis but was positive for pre-B cell Acute Lymphoblastic leukemia (ALL).

Discussion: Myelofibrosis was originally described in 1879 as the presence of excessive collagen or reticulin fibers along with abnormal hematopoiesis. Myelofibrosis is an uncommon entity in pediatrics with about 100 cases reported worldwide, therefore most of what is known is extrapolated from adults and yet its clinical process does not mimic the adult process. Pediatric myelofibrosis (PM) can be idiopathic or secondary to infections, metabolic disorders, or malignancies. The most common malignant etiologies tend to be AML, lymphomas, and rarely ALL. Infectious-wise, the most common etiology reported has been tuberculosis. It is well known that severe infection can cause bone marrow suppression, which resolves with time or treatment. There have been few cases reporting bacterial infections leading to fibrosis with complete recovery and later developing ALL. The mechanism of this is unknown and therefore it is difficult to ascertain whether there was initial spontaneous remission of the leukemia, or the infection led to the fibrosis which led to the leukemia. There are few similar reports and therefore difficult to decipher the pathophysiologic cause.

Conclusion: This case shows a unique presentation of ALL and the importance of close monitoring in patients with a history of pancytopenia as hematopoietic malignancies can be revealed with time.