Unilateral laterothoracic exanthem (ULE) developed in a 4-year-old-boy on m
aintenance therapy for acute lymphatic leukemia (ALL). This is the second r
eported case of an association between ULE and leukemia. The etiology of UL
E is unknown. Endemic cases, frequently associated signs of upper respirato
ry infections, and the occurrence of ULE in immunocompromised hosts are sug
gestive of an infectious process.