Altered mental status and low anion gap in a patient with sickle cell anemia: a case report

INTRODUCTION It is challenging to diagnose two coexisting medical conditions if the symptoms are overlapping. This is further confounded if the patient presents with an unexplained deterioration in mental status. A low anion gap or a zero anion gap is an uncommon clinical finding and has few differential diagnoses. This test therefore has important implications in correctly identifying underlying medical conditions. CASE PRESENTATION A 50-year-old African American male patient with sickle cell disease presented with refractory anemia, recurrent bone pains and encephalopathy. Routine testing failed to explain his mental deterioration. A laboratory finding of a low anion gap pointed in the direction of multiple myeloma as the underlying cause. This in turn led to an appropriate and timely course of treatment and clinical improvement. CONCLUSION We present a very rare case of sickle cell anemia with coexisting multiple myeloma. This case sparks an interesting discussion on the anion gap, of which a clinician should be aware. It highlights the importance of the use of a verifiable anion gap in diagnosing medical conditions beyond the routine diagnosis of acid base disorders.