The case reported concerned a patient 44 years old, affected by a systemic lupus erythematosus for 18 years and admitted for an acute respiratory distress due to a bronchopulmonary infection. After this episode an interstitial chronic lung disease is diagnosed (reticulonodular pattern on the chest X-ray, functional restrictive syndrome). The study of the transbronchial lung biopsy by electron microscopy revealed interstitial electron dense deposits. This observation focussed on the interest of this technic of morphological study mainly in chronic lung interstitial diseases.