Low back pain as an unusual presentation in a child with acute lymphoblastic leukaemia

Abstract

Acute leukaemia is the most common childhood cancer. The clinical presentation of acute leukaemia includes fever, pallor, bleeding tendencies, hepatosplenomegaly, lymphadenopathy and bone pains. This case is about a 7-year-old boy who presented with 2 months of progressive low back pain after jumping into the sea. Radiologic workup showed compression fractures in the T6–L5 regions of the spine. Trauma and osteogenesis imperfecta were considered initially until the patient developed the classic features of leukaemia. Analysis of the bone marrow aspirate, 2 months after the sea incident, revealed B cell acute lymphoblastic leukaemia (ALL). The low back pain subsided after a week of chemotherapy. A symptom that involves bone pain in a child needs thorough evaluation because a delay in diagnosis affects the outcome of treatment. ALL has been lingering at the time of his accident and this has caused weakening of his spine that resulted in much more severe injury than would have occurred in the absence of the ALL.

Background

Low back pain is fairly an ordinary complaint of children. Musculoskeletal aetiology is often considered when there is no organ involvement, and when laboratory results are normal. An increasing intensity of pain accompanied by kyphosis and limited ambulatory function warrants further evaluation that includes malignancy.

Bone involvement in children with acute lymphoblastic leukaemia (ALL) at diagnosis is reported in 21%–59% of the cases in the literature. This phenomenon is secondary to marrow infiltration by leukaemic cells. As a result, anaemia, leucopenia and thrombocytopenia, and symptoms secondary to these, become evident. However, when low back pain precedes the well-recognised signs and symptoms of leukaemia, diagnosis becomes challenging.

The purpose of this report is to share the case of a child with low back pain as an initial presentation of ALL. We highlight the importance of having a high index of suspicion that low back pain can be an atypical pre-leukaemic symptom, and that malignancy can be suspect when the pain increases in intensity.

Case presentation

A 7-year-old well child, with no family history of malignancy, presented with a 2-month history of low back pain after jumping into the sea while running from the shore. One week after the incident, he sought professional help. Thoracolumbar X-ray was done, which showed compression fractures of the T6–L5 vertebrae (figure 1). The doctor prescribed pain relievers. After 3 weeks of observation and without resolution of symptoms, a repeat X-ray showed a more pronounced vertebral collapse, and MRI revealed a biconcave appearance with a decrease in height of the vertebrae. Osteogenesis imperfecta was considered.

Figure 1.

X-ray of the thoracolumbar region showing compression fractures of the vertebral bodies T6–L5 (white arrows).

Investigations

The increasing intensity of low back pain associated with increasing curvature of the spine and difficulty in ambulating led to the patient’s confinement under the orthopaedic service of a hospital. MRI of the spine revealed a similar finding of compression fractures of T6–L5 vertebrae (figure 2A, B). The haematologic picture and metabolic workup revealed normal results: haemoglobin 13.3 g/L, haematocrit 37.5%, leukocyte count 7.2×10⁹/L, segmenters 83%, lymphocytes 13%, monocytes 3%, eosinophils 1% and platelets 379×10⁹/L. The patient was eventually discharged with a diagnosis of compression fractures and was prescribed with thoracic brace.

Figure 2.

MRI images demonstrating a biconcave appearance with decrease in height of T6 (A) down to L5 (B) vertebrae (white arrows).

Three weeks later, the patient’s medical condition worsened as he developed high grade fever, went into respiratory distress, developed haematochezia, and was subsequently admitted at the paediatric intensive care unit. Complete blood count revealed the following: haemoglobin 77 g/L, hematocrit 22%, leukocyte count 3.24×10⁹/L, neutrophils 11%, lymphocytes 71% and platelets 16×10⁹/L. The patient was then given antibiotics, meropenem and amikacin, for sepsis caused by Pseudomonas sp. Platelet and red cell transfusions were given accordingly. A repeat CBC after 2 days revealed: haemoglobin 85 g/L, hematocrit 24%, leukocyte count 0.76×10⁹/L, neutrophils 35%, lymphocytes 48% and platelets 16×10⁹/L. Lactate dehydrogenase was elevated (454.88 U/L), and alkaline phosphatase was slightly high (178.3 U/L). There was no hepatosplenomegaly nor lymphadenopathy and no bowel bladder dysfunction. Examination of the lumbosacral region revealed kyphosis, with limited motion of the lower extremities.

At this time, 2 months after the ‘jumping into the sea’ incident, haematologic disorder was highly considered. A diagnosis of B cell ALL was made based on the results of a bone marrow aspirate (figure 3) and flow cytometry. Chemotherapy was initiated after the infection was resolved.

Figure 3.

Image of bone marrow aspirate showing lymphoblasts (black arrows).

Outcome and follow-up

After a week of chemotherapy, the patient was relieved of his low back pain without any neurologic deficits. In addition, there was a notable remodelling of the patient’s kyphosis 3 months after the start of treatment. His complete blood count improved with a haemoglobin level of 12.1 g/L, leukocyte count of 2.9×10⁹/L and platelet of 170×10⁹/L. His follow-up X-ray, done 1 year after completion of his chemotherapy, showed complete remodelling of the affected vertebrae (figure 4).

Figure 4.

X-ray of the thoracic region showing complete remodelling of the spine 1 year after therapy. (white arrows).

Discussion

The predictive value of low back pain or vertebral fracture in the diagnosis of leukaemia is not well-documented. Most of the published facts are from case reports. Non-specific symptoms, such as low back pain in children, present with a diagnostic uncertainty to a clinician despite sufficient information from the clinical history, physical examination and diagnostic studies. In general, low back pain with vertebral collapse can be categorised as infectious, such as in Pott’s disease, as a genetic condition, such as in osteogenesis imperfecta or as a malignancy, such as in leukaemia. Osteogenesis imperfecta was the initial impression given on this patient. Forty per cent of children with acute leukaemia have at least one radiographic abnormality at presentation.¹ On the other hand, the frequency of malignancy in children with musculoskeletal symptom is <1%, with ALL being the most common diagnosis.² When vertebral collapse is the initial presenting sign of leukaemia, the characteristic findings include the absence of significant organomegaly and lymphadenopathy, normal to low leucocyte count, normal platelet, uric acid and lactate dehydrogenase. The patient exemplifies the above description.

Bone and joint pain in ALL can occur as an initial symptom of the disease, while vertebral fractures can occur as a complication of treatment. Cancer cell infiltration of the periosteum or expansion of the bone marrow by leukaemic cells is responsible for the initial symptom of bone pain, on one hand. The osteopenic effect of steroids is the aetiologic cause of compression fracture of the vertebral bodies, on the other. One study has reported that 16% of children with ALL developed vertebral fractures 12 months after the initiation of therapy.³

Based on several published case reports, the time from initial symptoms to definitive diagnosis ranges from 3 weeks to 3 months.^{4 5} With this patient, the time from the incident of jumping into the sea up to the time of diagnosis was 2 months. The delay in our diagnosis was due to the lack of symptoms as well as the absence of laboratory findings indicative of leukaemia.

Studies have shown that poorly defined presenting symptoms have made childhood ALL difficult to diagnose in the absence of organomegaly or diffuse lymphadenopathy. Most of the related literature in this area are case report documentations of painful vertebral fractures as an initial presenting symptom of childhood ALL.

In a multicentre clinical trial of 186 children (median age: 5.3 years.) with newly diagnosed ALL, Halton et al⁶ found that 29 patients (16%) had vertebral compression fractures. They concluded that their results could have been an underestimation since chest radiographs may not be optimal for visualisation of vertebral bodies. Another interesting finding was that many of the children with vertebral fractures (45%) were asymptomatic.

We reviewed 15 case reports on children with ALL, and found only 1 report in which bone involvement became worse despite leukaemic remission.⁷ All other cases showed that the back pain was relieved after chemotherapy.

We found two reports of ALL that was diagnosed on presentation of compression vertebral fractures and back pain associated with trauma.^{8 9} Like our patient, both cases had persistent and worsening back pain, and diagnosis was delayed.

All the other case studies included children with ALL whose vertebral fractures were the initial and only presenting symptoms that led to the diagnosis of ALL.^{5 10–16} Radiologic and other imaging modalities provided evidence that the associated back pain among children with ALL potentially involves bone morbidity, including osteoporosis and vertebral fractures. Furthermore, these studies provide evidence that back pain and vertebral compression fractures may be the first manifestations of ALL of childhood.

In our patient, acute leukaemia was considered when the constitutional signs, symptoms and laboratory features common to the condition surfaced, after a 2-month period of low back pain, subsequent vertebral fracture, kyphosis and decreased mobility. Bone marrow aspirate examination showed lymphoblasts, and flow cytometry revealed a more conclusive immunologic finding consistent with a blast population of B lymphoid lineage. The evolution of the signs and symptoms over time has led to a strong possibility that the back pain and compression fractures may be attributed to the ALL and were out of proportion to the injury caused by his act of jumping into the sea. Furthermore, ALL that was occult but present at the time of the injury had caused weakening of the spine that resulted in much more severe injury than would have occurred in the absence of the ALL.

Our diagnosis of B cell ALL is consistent with the typical attributes of this phenotype: bone involvement, young male, low white blood cell count and better prognosis.¹⁷ Chemotherapy resulted in immediate relief from symptoms. The patient became symptom-free 1 week post-induction of treatment. Remodelling of the patient’s kyphosis was considerably remarkable 3 months after the treatment was started.

Patient’s perspective.

My backbone pain started when I jumped and landed a little too hard on the shore. I remembered back then that the pain was so bad that I had a hard time breathing. Ever since the pain started, my activities have changed considerably. I couldn’t move and play as much because I used to wear a binder around my torso to limit the movement of my back. The pain only subsided when I lay down. I also had a hard time bathing alone because it was painful to bend down, but my mother was always there to help me.

The pain started to fade when I was admitted at Batangas Medical Center. I didn’t know how I felt when they told me I had cancer because I had no idea what cancer is back then. During my stay at the hospital, I was always tired and hungry. Sometimes, I would feel lonely, but my family and the hospital staffs were always there supporting me which made things better.

When I went back to our province, I started my chemotherapy which made my hair fall out and made me feel hungry most of the time. I didn’t get to see my friends because I was enrolled in homeschool programme. However, my cousins would always play with me and keep me entertained.

After years of treatment, I feel as if I’m a normal kid now. I get to play, run around and jump without feeling any pain. I also can bathe now alone without needing assistance from my mother. I hope that I finish my treatment and finally be cancer free.

Learning points.

• Low back pain in a child needs to be thoroughly evaluated. A lingering condition, however, unusual, such as cancer, should be considered if the degree of weakness is not proportionate to the overt incident, initially thought to be the cause. Acute lymphoblastic leukaemia could have been detected sooner had the attending physicians suspected this at the time of initial consult. Differential diagnosis such as a malignancy should be considered because a delay in diagnosis affects the outcome of treatment.

• A high index of suspicion for malignancy is needed in patients presenting with worsening low back pain.

• Chemotherapy provides rapid relief of symptoms and bone remodelling once intervention is instituted.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).