Introduction: Diffuse brain disease in systemic lupus erythematous (SLE) can be difficult to assess because of the sparse biological expression of the disorder, resulting in usually normal neuroimaging and laboratory findings. For this reason, it is likely that patients without a previous SLE diagnosis that presented initially with a pure psychiatric disorder, as psychosis or depression, can remain undiagnosed, and, in fact, they are exceptionally reported. As a biological marker, antiribosomal P protein antibodies have been closely related to SLE psychosis although their pathogenic role and specificity is under discussion.
Clinical case: A young woman, without relevant medical history, presented with an acute psychotic catatonic picture, suspected organic in nature due to the existence of persistent mild CSF pleocytosis, while neuroimaging and laboratory studies were negative, including antinuclear and antiribosomal antibodies. Finally, a SLE diagnosis could be established because of a strong lupic band phenomenon in skin biopsy.
Conclusions: It is important to maintain a high suspicion of SLE in acute psychotic patients, especially if atypical features are present. As the biological expression of the disorder in such cases may be elusive, we propose the study of lupus band in skin biopsy for these patients, regardless the absence of antiribosomal antibodies.