Dengue, an arboviral infection that classically presents with fever, joint pains, headaches, skin flush and morbilliform rashes. Dengue viruses (DENV) belong to the family Flaviviridae and there are four serotypes of the virus referred as DENV-1, DENV-2, DENV-3 and DENV-4 . All four serotypes can cause the full spectrum of disease including subclinical infection to a mild self limiting disease, dengue fever and severe disease that may be fatal including the dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS).
Around 2.5 billion people around the world live in dengue endemic countries and are at risk of developing DF/DHF. Dengue is endemic in most countries of the South East Asia region where the detection of all four serotypes has now rendered these countries hyperendemic [2, 13, 14]. Dengue viral infections have become endemic in Sri Lanka since the mid 1960s, and since then the infections have increased dramatically over the past three decades [4, 13, 15].
We described this case scenario of GBS that had been preceded by a proven episode of dengue fever. Both episodes were not severe in their natural history as the patient did not develop plasma leak during the dengue infection and respiratory failure during subsequent GBS. The patient made recovery which was probably due to early use of plasmapheresis. Neurological manifestation associated with dengue fever has been reported from 25 different countries from Asia–Pacific, Americas, Mediterranean and Africa . The involved ages had ranged from 3 months to 60 years in both sexes, being more common in children . The incidence of neurological symptoms and complications among dengue patients varied from 1 to 25 % of all dengue admissions [2, 5, 12]. These manifestation included encephalopathy, GBS, acute motor weakness, seizures, neuritis, hypokalaemic paralysis, pyramidal tract signs, etc. [2, 5, 16].
There are a few previous reports that described GBS in patients with dengue particularly in adults. Gupta P et al.  reported a case of post-dengue GBS in a 24-year old unmarried male presenting with acute flaccid weakness of the lower limbs following a febrile illness of 3 days. The PCR for dengue was positive and IgM and IgG antibodies for DENV were found positive. The patient had been treated with intravenous human immunoglobulins and had a quick and complete recovery . Similarly, Nee Kong Chew et al.  reported two cases of post-dengue GBS. The first case was a 43-year old woman with GBS presenting with the weakness of all four limbs and respiratory distress. She required assisted ventilation and immunomodulation treatment. The second case was a 51-year old man with bilateral facial weakness and numbness of extremities without motor weakness and recovered . In 2012, Qureshi NK et al. reported a case of GBS following dengue fever in an adult patient. The case was a 39-year old female presented with acute flaccid weakness of both upper and lower limbs which developed in ascending and progressive fashion following a febrile illness of 3 days. She had positive IgM for DENV and was treated with intravenous immunoglobulins. In all these case reports, the onset of GBS occurred after recovery from the initial dengue infection similar to the present case report. The mechanism for post-dengue GBS is not fully understood. There is evidence that this is an immune-mediated neurological disease [17, 18]. Pro-inflammatory substances that participate in immune response to DENV such as TNF, complement, interleukins may have important role in the pathogenesis of GBS . Immune response evoked by dengue fever may in turn cross-react with peripheral nerve components because of sharing of cross-reactive epitopes. This immune response can be directed towards the myelin or axon of peripheral nerves .
Several randomized clinical trials indicate that plasma exchange is more effective than supportive treatments in reducing the median time taken for recovery in GBS [5, 18]. Intravenous immunoglobulin (IVIg) appears as effective as plasma exchange and IVIg may be preferred because of its low side effect profile and ease of administration [5, 18]. Corticosteroids alone do not alter the outcome of GBS, and there is insufficient evidence to support their use in combination with immunoglobulin [5, 18]. Other treatments such as CSF filtration remain experimental and unproven . Our patient was treated with seven sessions of plasma exchange and showed gradual improvement.
In our patient, the presence of a positive dengue-specific IgM antibody test indicates acute dengue illness. Neurological manifestations, pattern of electrophysiological study and the typical CSF findings were consistent with the diagnosis of GBS. Development of GBS in about 10 days after the initial manifestation of dengue support the association of these two conditions. Verma et al. shows that the patient presents with neurological syndromes like myelitis, myositis, GBS etc., dengue infection should be kept in differential diagnosis and should be ruled out especially during dengue outbreaks .