A 6-year-old-girl presented with complaints of difficulty in walking for 5 days. Initially, the child started limping on the left side, followed by unable to bear weight; within two days, the right lower limb also got involved and she became non-ambulatory. She also complained of dull aching pain in lower limbs, especially in the upper thigh, more on the left side. There was no history of proceeding febrile illness, trauma or intra-muscular injection. She was completely immunized as per the national immunization schedule. She had tenderness in the left flank, lower back and bilateral thigh, keeping the hips in a semi-flexed position, not allowing any passive movement or formal tone examination. Even knee jerks could not be elicited bilaterally. In the left hip joint power was 2/5 and 3/5 power in the right knee, left hip and knee joint. A clinical possibility of acute flaccid paralysis (AFP) was kept, with a differential diagnosis of Guillain-Barré syndrome (GBS), viral myositis, polymyositis, transverse myelitis, paralytic polio myelitis, Perthes disease, septic arthritis of the hip joint and pseudoparalysis due to unnoticed trauma, or with pelvis/femur fracture. On investigations, X-ray of the hips, nerve conduction study and serum creatine phosphokinase were normal. Ultra-sonogram revealed a heterogeneous collection in left iliopsoas muscle, extending to the pelvis and inguinal region. Pus was drained by percutaneous pigtail catheter and she responded favorably to intravenous vancomycin and she was able to walk after three days.

Although predominant causes of painful, hyporeflexic weakness of bilateral lower limbs are GBS and viral myositis, often pseudoparalysis due to trauma, scurvy or referred pain from the loin, lower back or hip joint may mimic GBS, thereby causing diagnostic confusion [1]. The classic triad of psoas abscess (fever, flank pain, and limitation of hip joint movement) can be found only in 30% of patients [2].

The atypical presentation with bilateral painful gait instability in absence of fever, trauma or intramuscular injection in our case clinically resembled GBS or pathology localized to lumbosacral plexus or spinal cord. However, instead of performing costly and tedious investigations like MRI and nerve conduction study, simple ultrasonography may clinch the correct diagnosis easily. Pseudoparalysis in children under 15 may be caused due to various etiologies like skeletal trauma, lymphadenitis or muscle aches from a viral illness, transient synovitis, septic arthritis, osteomyelitis, pyomyositis, fasciitis, cellulitis, rheumatological diseases such as juvenile idiopathic arthritis, acute rheumatic fever and malignancies like sarcoma and leukemia [3,4]. Hence, atypical presentation of iliopsoas abscess requires a high index of suspicion on part of pediatricians, to establish a timely diagnosis.

1. Panda PK, Sharawat IK. Seizure in a child with Guillain-Barré syndrome: Association or coincidence! Indian Pediatr. 2020;57:79.

2. Charalampopoulos A, Macheras A, Charalabopoulos A, Fotiadis C, Charalabopoulos K. Iliopsoas abscesses: Diagnostic, etiologic and therapeutic approach in five patients with a literature review. Scand J Gastroenterol. 2009;44:594-9.

3. Mitchell PD, Viswanath A, Obi N, Littlewood A, Latimer M. A prospective study of screening for musculoskeletal pathology in the child with a limp or pseudoparalysis using erythrocyte sedimentation rate, C-reactive protein and MRI. J Child Orthop. 2018;12:398-405.

4. Agarwal A, Shaharyar A, Kumar A, Bhat MS, Mishra M. Scurvy in pediatric age group – A disease often forgotten? J Clin Orthop Trauma. 2015;6:101-7.