A 25‐year‐old man, diagnosed with systemic lupus erythematous (SLE) 6 months prior and undergoing a workup for LUPUS NEPHRITIS, was brought to the emergency department by his family for weakness and altered mental status, for 1 day. Per the family, the patient complained of generalized body weakness on the morning of admission. Subsequently, he stopped talking. Six days before admission he had a seizure and was started on Keppra. The family said the patient smoked marijuana daily but had no other toxic habits. On physical exam, he was afebrile, BP 189/96, HR 120, RR 18. He was awake and alert but did not respond verbally to questions or follow commands. He moved all his limbs spontaneously. He had an erythematous facial rash in the malar distribution with mild scaling. Labs showed WBC 1500/μL, platelets 109,000/μL, AST 374 U/L, ALT 231 U/L, alkaline phosphatase 139 U/L. A CT scan of the head was negative for any infarction or intracranial hemorrhage. The patient was seen by his rheumatologist, and serologies were sent. He was evaluated by neurology and had an MRI and EEG, which were negative for acute intracranial pathology or seizurelike activity. A presumptive diagnosis that the patient was experiencing the after effects of using marijuana laced with psychoactive chemicals was made, based on the negative data. On hospital day 3, the results of his rheumatologic workup came back, and he had an elevated anti–ribosomal P protein antibody > 8 AI (normal < 1 AI). Based on this positive lab result, he was started on 1 g of Solu‐Medrol IV daily for lupus cerebritis and after a 3‐day course, his altered mental status and catatonia improved. He was discharged home soon after, doing well.
We present this case as an example of why we must avoid premature diagnostic closure in cases of altered mental status in the setting of illicit drug use. Nervous system involvement occurs in 24%–50% of all lupus patients in the United States at some time during the course of their illness. Initially, our patient's symptoms were attributed to the use of marijuana, based on negative studies for alternative diagnoses with a normal MRI and EEG. For neuropsychiatric lupus, up to 67% of patients will have abnormal MRI scans and EEG abnormalities are seen in 50‐90% of patients with SLE. However, these tests are not as specific for lupus cerebritis as the anti–ribosomal P protein antibody, which is a good diagnostic test with specificity reported as high as 80% in some studies. Because the diagnosis of lupus cerebritis was entertained on admission, this test was sent, and the result enabled the patient to be diagnosed and treated appropriately.
It is important to distinguish between altered mental status caused by illicit drug use versus true organic causes in the setting of SLE, and the physician should be aware of vital diagnostic tools such as the anti–ribosomal P protein antibody that are available to aid in diagnosis.