Incomplete Stevens-Johnson syndrome (SJS) is a rare reactive skin condition. Most cases are occurred in children and all are associated with Mycoplasma pneumoniae (M. pneumoniae) infection. We reported an unusual case of a 6-year-old boy who developed the presentation of isolated mucosal erosion with a lack of skin findings, which indicated incomplete SJS after two weeks of carbamazepine (CBZ) administration. Findings of positive HLA-B*1502 allele supported a possible causative influence of carbamazepine inducing SJS. Interestingly, this patient was tested negatively for M. pneumoniae. This is a significant finding since there is no previous report of incomplete SJS without M. pneumoniae infection. Discontinuation of CBZ and administration of systemic corticosteroids were accomplished to treat SJS, which resulted in complete recovery.
Our interesting findings highlighted the manifestation of incomplete SJS, which can present with other causes rather than M. pneumoniae infection. Early manifestation of mucosal change without typical skin lesions should not be neglected in the diagnosis of incomplete SJS.

Keywords: Incomplete/Atypical Stevens-Johnson syndrome, Mycoplasma pneumoniae