Objective. Eating disorders commonly present with nonspecific findings, masquerading as other, more common etiologies of malnutrition and wasting. In low-prevalence populations, these ambiguities can complicate clinicians' diagnostic reasoning, resulting in delayed or missed diagnoses. Method. We report the atypical case of a 51-year-old male with a five-year history of unexplained weight loss despite extensive past medical evaluation. Previous documentation of profound lymphopenia and bone marrow atrophy had not been linked to a known association with eating disorders. Results. Evaluation for medical etiologies of wasting was negative. Following psychiatric evaluation, the patient was diagnosed with an eating disorder, not otherwise specified, and admitted to a specialized nutritional rehabilitation program. Conclusion. The nonspecific clinical history, physical exam, and laboratory abnormalities of eating disorders can make these diagnoses challenging and delay appropriate treatment. Clinicians should consider eating disorders in patients with malnutrition, severe lymphopenias, and gelatinous marrow transformation early in their workup, so as to avoid potentially negative outcomes.