 Aphthous @-@ like ulceration also occurs in conditions involving systemic immuno @-@ dysregulation , e.g. cyclic neutropenia and human immunodeficiency virus infection . In cyclic neutropenia , more severe oral ulceration occurs during periods of severe immuno @-@ dysregulation , and resolution of the underlying neutropenia prevents the cycle of ulceration . The relative increase in percentage of CD8 + T cells , caused by a reduction in numbers of CD4 + T cells may be implicated in RAS @-@ type ulceration in HIV infection . 
