A 44-year-old woman presented at the Emergency Department (ED) with cough and dyspnea started 2 days prior. She was an active smoker, and she had a history of neurofibromatosis type 1(NF) diagnosed about 20 years prior by biopsy of the first nodule on the lower lip without lung involvement. At presentation, the patient showed sinus tachycardia (110 beats/min), tachypnea (respiratory rate: 28 breaths/min), oxygen saturation 92 % on room air, and body temperature 37.6°C.Physical examination revealed several café-au-lait maculae and several nodules on her trunk.Pulmonary examination showed reduced breath sounds bilaterally associated with bilateral wheezes.The 12-lead EKG demonstrated a normal sinus rhythm at a rate of 99/min. Chest radiography revealed an image suggestive for pulmonary hyperlucency, without acute pulmonary consolidation and without bronchiectasis ( Fig. 1). Laboratory tests revealed an elevated WBC (12.9 9 10 9 /L) and fibrinogen level (479 mg/dL). Arterial blood gas analysis showed hypoxia (PaO 2 66.4 mmHg) with normal pH and PaCO 2 values.Based on the initial presentation, normal EKG, hypoxia and the presence of elevated inflammatory markers in the laboratory tests, pulmonary infection was considered.Thus, oxygen therapy (2L/min) by nasal probes and antibiotics (Levofloxacin 750 mg, PO qd) were started. On the second day, the hemodynamic and respiratory status did not improve significantly. For this reason, we performed a chest ultrasonography that showed two sub-pleural hypoechogenic images, 0.5 and 0.7 cm in diameter, respectively, in the lower field of left lung with rear-wall reinforcement and a localized alveolar-interstitial syndrome (Fig. 2).On the basis of the result of chest ultrasonography, we considered the clinical presentation as the lung involvement of NF. So, we added to the current therapy, methylprednisolone sodium succinate (60 mg daily, IV), and the association of beclomethasone, ipratropium bromide, and salbutamol (0.8, 0.25 and 5 mg, respectively, nebulized bid). A significant improvement of respiratory status was noted in a few hours. The ultrasonographic findings were subsequently confirmed by a chest high resolution computed tomography (HRCT) that showed diffuse small rounded thin-walled lung cysts (1 cm), predominant in the lower left lobe. Same lung cysts had a diameter of 3.3 cm (Fig. 3). These abnormalities had a random distribution, prevalent on the sub-pleural side with paraseptal emphysema characteristics of neurofibromatosis. The chest HRCT also showed a moderately thickened appearance of the walls of some pyramids in basal bronchial branches, which could be compatible with bronchiectasis. This apparent discordance with the chest X-ray study can be explained by the fact that HRCT demonstrates higher sensivity than chest radiography in the detection of bronchiectasis.Von Recklinghausen's disease or neurofibromatosis type 1 is an autosomal dominant dysplasia of ectoderm and mesoderm with a prevalence of 1 in 3,000. The typical characteristic is the presence of neuro...