an 8-year - old boy with the underlying condition of prematurity had normal developmental milestones . he presented with sudden onset , profoundly blurred vision ( oculus uterque [ ou ] ) accompanied by prodromal symptoms of upper respiratory infection . initial ocular examination revealed that his best - corrected visual acuity ( bcva ) had deteriorated to light perception only ( oculus dexter [ od])/hand motion ( hm ) at 70 - 80 cm ( oculus sinister [ os ] ) , a fixed and dilated pupil ( 6.0 mm ) , and normal fundus appearance [ fig . 1 ] . a visual field ( vf ) examination could not be performed because of severe visual loss . 2 ] revealed that the retinal nerve fiber layer thicknesses were within the normal range . 3 ] showed severe prolonged latency ( ou ) . the brain magnetic resonance image ( mri ) did not show a brain lesion nor optic nerve enhancement in the t1-weighted image with contrast . laboratory analyses revealed a high mycoplasma - igm titer ( + , > 75 bu / ml ) in his blood , but the glucose ( 62 mg / dl ) and total protein ( 18.6 mg / dl ) levels in his cerebrospinal fluid ( csf ) were within normal limits . based on the profile above , bilateral on associated with m. pneumoniae infection was suspected . color fundus did not reveal papillitis or an active retinal lesion disc optical coherence tomography ( oct ) . disc oct revealed normal bilateral disc appearance and nerve fiber layer thickness visual evoked potential ( vep ) . pattern vep showed a severely prolonged latency and aberrant waves a pulse steroid therapy of intravenous methylprednisolone ( 750 mg / day ) was given for 3 days followed by oral prednisolone ( 10 mg / day ) . however , because the bcva persisted at hm ( ou ) after the 3-day pulse therapy , an intravenous immunoglobulin ( 1 g / kgday ) was prescribed for 2 days . after the 3-day pulse therapy , the initially fixed and dilated pupil ( size , 6.0 mm ) responded to light ( size , 3.5 mm ) , but a relative afferent pupillary defect ( rapd ) was still noted in the right eye . his bcva improved to 12/20 ( od ) , 6/20 ( os ) and the vf [ fig . 4a ] showed a severely constricted vf with a central tunnel ( od)/inferior arcuate vf defect ( os ) 2 weeks after pulse therapy . his visual outcome dramatically improved with a bcva of 20/20 ( od ) , 20/20 ( os ) and an improved vf result 7 weeks after treatment [ fig . 4b ] , and these factors improved further at 15 weeks after treatment [ fig . initially 2 weeks after treatment ( a ) , a vf defect was noted with a severely constricted vf with a central tunnel ( oculus dexter)/inferior arcuate vf defect ( oculus sinister ) . progressive improvement was noted 7 weeks after treatment ( b ) and 15 weeks after treatment ( c ) on , which is strongly associated with multiple sclerosis , infectious causes should be given a high priority in young patients . a review article indicated that specific infectious pathogens such as measles , mumps , chickenpox , rubella , brucella , pertussis , mononucleosis , and epstein - barr virus have been reported for pediatric on ; furthermore , this review proposed that postinfectious on is the result of an autoimmune reaction to the infection . bilateral involvement with profound visual loss is more common in on in children than in adults . the vep signal may initially present as an absent or diminished amplitude , with a more abnormal latency than is observed in adults . m. pneumoniae is an atypical pathogen that mainly causes respiratory infection and is among the most important bacterial causes of  atypical  community - acquired pneumonia with overall prevalence of 22.7% . the most common extrapulmonary complications of m. pneumoniae are neurological , such as encephalitis , myelitis , and central white matter disease . it may also show ocular involvement such as conjunctivitis , third or sixth nerve palsies , homonymous hemianopia , nystagmus , anterior uveitis , and very rarely , optic neuropathy . although the primary diagnosis of m. pneumoniae - associated disease is based on clinical presentation , elevated immunoglobulin titers in the serum are an acceptable diagnostic confirmation in clinical practice . due to the rare incidence of on associated with m. pneumoniae infection , we reviewed articles about on after m. pneumoniae infection published from 1998 to 2011 [ table 1 ] . in total , five patients with m. pneumoniae - induced on reported in the available literature . the following characteristics were noted : all cases had prodromal symptoms of respiratory tract infection , only two on cases occurred in children ; four cases had bilateral profound visual loss , one case had a vf defect of disclosed marked restriction , four cases did not have a light reflex ; three cases had papillitis , and two cases had abnormal mri findings . compared to the patients listed in table 1 , our patient was the first to present with monosymptomatic visual loss without papillitis , neurological symptoms , and an abnormal mri ; furthermore , papillitis is the common presentation of on in children , but our patient presented with retro - bulbar form . literature review of m. pneumoniae - induced optic neuritis with clinical manifestations direct invasion of the cns and a postinfectious immune response are among the suggested mechanisms of m. pneumoniae extrapulmonary complications . another study suggested an autoimmune mechanism because antibodies to myelin and neural tissue have been detected in some cases and the removal of these antibodies by plasmapheresis ameliorated neurological symptoms . the on treatment trial suggests intravenous administration of methylprednisolone followed by oral prednisolone for a fast recovery and low recurrence , but no effect on final visual outcome . although the management of on is well - described in adults , evidence - based , prospective clinical data on its management and treatment in a pediatric population is scarce . the current treatment of pediatric on , consisting of 3 - 5 days of intravenous methylprednisolone ( 4 - 30 mg / kgday ) followed by oral corticosteroid . the alternative treatment includes intravenous administration of immunoglobulin and plasmapheresis while being refractory to corticosteroid . however , the effect of immunomodulation on visual recovery has not been established . as for our patient , improvement could not be recognized as the attribution to steroid or immunoglobulin therapy . regarding the prognosis of pediatric on , visual recovery is excellent in most cases , especially in younger children ( < 6 years of age ) . in our patient , the clinical course of on presumably due to m. pneumoniae infection was recovery of the pupil response to light 3 days after pulse therapy and an improvement of the va to the normal range in 7 weeks ; however , the vf defect persisted 2 months after on onset . evaluation of anti - mycoplasma antibodies ( igm and igg ) and a cns survey ( mri and csf study ) should be performed routinely when on is suspected , especially in children . the visual outcome was favorable in our case with recovery of visual acuity 2 months after treatment .
herein , we report the clinical findings , treatment choice , and clinical course of a rare case of mycoplasma pneumoniae ( m. pneumoniae ) infection with the sole manifestation of optic neuritis ( on ) . to the best of our knowledge , 
 this is the first case presenting monosymptomatic visual loss without papillitis , neurological symptoms , and abnormal findings on brain imaging . 
 related articles about on after m. pneumoniae infection were reviewed to summarize the clinical presentation , possible mechanisms , clinical survey , treatment , and prognosis of this condition . 
 we propose that a mycoplasma profile is necessary in children who present with on , especially when this condition is accompanied by prodromal symptoms of the respiratory tract infection .