Paediatric pure motor Guillain–Barré syndrome without antecedent infection: An uncommon clinical scenario

INTRODUCTION

Guillain–Barré syndrome (GBS) is a rapidly progressing autoimmune condition resulting in peripheral nerve involvement. It is considered the leading cause of acute flaccid paralysis worldwide. Clinically, it is characterised by bilateral limb weakness along with diminished or absent deep tendon reflexes, typically progressing to maximum severity within 4 weeks. Mortality is reported in approximately 5% of cases.^[1]

Although the pathogenesis of GBS is not fully elucidated, it is believed to involve both antibody-mediated and cell-mediated immune responses. In many instances, the syndrome follows an infection; among the known triggers, Campylobacter jejuni is most frequently linked to the onset of GBS.^[2] The proposed mechanism is molecular mimicry, wherein structural similarities between microbial antigens and components of the peripheral nervous system result in an autoimmune attack.^[3]

GBS is categorised into multiple subtypes based on clinical presentation, electrophysiological findings and pathological features. Major variants include acute motor axonal neuropathy (AMAN), acute motor-sensory axonal neuropathy and acute inflammatory demyelinating polyradiculoneuropathy. Involvement of cranial nerves is commonly observed, with facial palsy being the most frequent, subsequently presenting with bulbar dysfunction, ocular muscle paralysis (ophthalmoplegia), and, in rare instances, weakness of the tongue muscles.^[4]

Diagnosis is primarily clinical but supported by investigations to rule out alternative aetiologies. Nerve conduction studies are essential, often revealing early changes such as prolonged F-wave latencies, delayed distal motor responses or dispersed compound muscle action potentials. Cerebrospinal fluid (CSF) analysis commonly reveals an elevated protein level with a normal white cell count, a phenomenon known as albuminocytologic dissociation. Additionally, magnetic resonance imaging of the lumbosacral spine may reveal gadolinium-enhanced nerve roots, further supporting the diagnosis.^[5,6]

Intravenous immunoglobulin (IVIg) and plasma exchange constitute the major therapeutic modalities, each proven to be effective in clinical practice in altering disease progression. Supportive rehabilitation – including physical, occupational and speech therapy – is critical to optimise functional recovery.^[6]

While GBS can affect individuals across all age groups, paediatric cases are relatively uncommon and may present atypically, leading to diagnostic challenges. Among the clinical variants, pure motor GBS without a preceding infection is particularly rare in children.^[7]

This report highlights a clinical presentation of a 9-year-old male child diagnosed with pure motor GBS in which there was rapidly progressive weakness of limbs experienced in the absence of any antecedent illness. The present case emphasises the value of clinical vigilance and early therapeutic action in atypical paediatric manifestations of GBS.

CASE REPORT

A previously healthy 9-year-old male child was brought in with a 3-day history of progressive bilateral lower limb weakness and pain, resulting in difficulty walking. He had experienced a hypoglycaemic episode at school but denied fever, recent trauma, vaccination or gastrointestinal/respiratory symptoms. On physical examination, he was conscious, oriented and afebrile. His vital signs were as follows: pulse rate – 103/min, blood pressure – 118/78 mmHg, SpO2 – 100%, respiratory rate – 22/min, and temperature – 98°F. Neurological evaluation revealed absent reflex responses at the patellar and ankle joints bilaterally, with bilateral flexor plantar responses. Cranial nerves and upper limb reflexes were normal. There were no signs of meningeal irritation.

DISCUSSION

GBS typically presents with symmetrical limb weakness associated with diminished or absent elicitable tendon reflexes, progressing to peak severity within 4 weeks.^[1,9] Epidemiological data indicate a higher incidence in males, with an estimated global occurrence of 1–2 cases/100,000 individuals annually.^[10] This case describes an atypical paediatric GBS presentation characterised by a pure motor neuropathy and absence of typical antecedent infections. The classical diagnostic triad of GBS includes acute flaccid paralysis, areflexia and elevated CSF protein with minimal pleocytosis (albuminocytologic dissociation).^[11] Although CSF analysis was not performed in this case, the diagnosis was supported by NCV findings and the clinical course. The patient’s condition improved significantly following appropriate medical intervention, particularly in mobility. Upon discharge, he was instructed to adhere strictly to the prescribed medication regimen and follow-ups for continued recovery. At follow-up one week later, the patient remained clinically stable and demonstrated continued improvement in lower limb strength.

Pure motor GBS is less common but may present more frequently in children than is recognised. It is often associated with better outcomes and minimal autonomic dysfunction. The absence of sensory involvement and the predominance of motor axonal features suggest an AMAN subtype.^[12]

The pathogenesis of GBS involves molecular mimicry following infections, yet no triggering illness was evident in this case. Similar cases have been reported in the literature, although they are rare. Early initiation of IVIg is known to shorten recovery time and improve prognosis. In addition, attention to metabolic derangements such as hypocalcaemia and vitamin D deficiency may be important in the holistic management of these patients.^[2-6]

CONCLUSION

The report emphasises the clinical relevance of recognising GBS as a potential diagnosis in children presenting with acute flaccid paralysis, even in the absence of antecedent infections. Pure motor variants can mimic other neuromuscular conditions and require timely neurophysiological evaluation. Early administration of IVIg and supportive care remains the cornerstone of treatment. Further studies are warranted to understand prognostic indicators and long-term outcomes in paediatric pure motor GBS.