Recurrent arthritis: an unusual diagnosis

Case report

A five-year-old girl was admitted with complaints of multiple similar episodes of fever and painful swelling of the right knee over an eight-month period. Each episode lasted for 10–15 days and improved on taking traditional medications, followed by an asymptomatic period of two months after which symptoms reappeared. There was no history of tuberculosis in the family. The child was developmentally normal. Childhood immunisation was complete. A full blood count (FBC) and bone marrow examination performed in a previous healthcare facility were both normal (this was probably done as the child had complaints since the last eight months and steroids are a part of the treatment for chronic arthritis; these investigations were done to rule out leukaemia before starting steroids).

On examination, she was pale and had palpable hepatosplenomegaly without lymphadenopathy. The right knee was tense and swollen. She had microcytic hypochromic anaemia (Hb 88 g/L) with no atypical cells on peripheral smear and a total white cell count of 7.9 × 10³/µL and platelet count of 343 × 10³/µL. Her erythrocyte sedimentation rate was 10 mm/h, C-reactive protein was <1 mg/L, and antinuclear antibodies and rheumatoid factor were negative. An ultrasound of the right knee demonstrated an effusion; 2 mL of clear fluid aspirated showed some pus cells but no bacterial growth.

Juvenile idiopathic arthritis, tubercular arthritis and septic arthritis were considered. Treatment with ceftriaxone and vancomycin were given in view of possibility of septic arthritis, together with naproxen for pain. After an initial improvement, fever and swelling of the right knee reappeared. The size of hepatosplenomegaly had increased but a repeat fever work-up was inconclusive. Another bone marrow aspiration, however, demonstrated the presence of eosinophilic precursors with 9% blasts positive for CD10, CD19, CD20, CD79a, CD34 and HLADR, therefore suggestive of B cell origin. The supposition that steroids had induced suppression of blast cells was held open, but a final diagnosis of acute B cell lymphoblastic leukaemia (ALL) was confirmed. Unfortunately, the child left against medical advice after only one week of treatment (as the child had been on treatment from another healthcare facility for the last eight months and bone marrow examination was previously normal, her parents were not receptive to the final diagnosis and wanted to seek an opinion from some other higher centre and also wanted to try alternative medicine).

Discussion

The differential diagnosis of a child with fever, painful swollen joints and organomegaly includes infection-related diseases (such as septic arthritis or reactive arthritis), rheumatological disorders and haematological malignancy.

Childhood leukaemia may present with varied clinical presentations, some of which mimic orthopaedic conditions.

Up to 6.4% of children with leukaemia may present with osteoarthritic manifestations, most commonly asymmetric oligoarthritis. ¹

Joint involvement is considered to be secondary to a local reaction to bony, periosteal or capsular infiltration by malignant cells. This can occasionally cause bleeding into the joint or crystal-induced synovitis.^2,3

The duration from onset of symptoms to the final diagnosis of leukaemia may be lengthy, measured in weeks to months. Patients with childhood leukaemia presenting with predominantly musculoskeletal complaints are more likely to have normal FBC results.^4,5