Author(s)

Diana Afonso P, Palas J, Furtado MJ

Patient

male, 54 year(s)

A 54-year-old male patient presented with dry cough and dyspnoea on exertion. Chest radiograph revealed a reticulonodular pattern. HRCT showed a combination of nodules and cysts.

A 54-years old male patient with no notable medical history presents with dry cough and dyspnoea on exertion. Physical examination was unremarkable. A standard chest radiograph revealed an extensive reticulonodular pattern, as well as small left pleural effusion. In order to better characterise those findings, HRCT was performed. It showed a combination of multiple small pulmonary nodules, some with cavitation, and thin-walled infracentimetric cysts, distributed bilaterally and diffusely throughout the lung, but more conspicuous in the upper and medium lung fields.

Langerhans cells histiocytosis (LCH) encompasses a spectrum of disorders of unknown aetiology. In adults, pulmonary involvement occurs mostly as a single-system pathology; if not, pulmonary involvement in patients with systemic manifestations is rarely at the forefront of the clinical scenario[1].
Pulmonary LCH, also know as pulmonary eosinophilic granuloma or histiocytosis X, is uncommon and occurs almost exclusively in smokers (95-90%). There is an incidence peak at 20-40 years of age and no sex predilection. Symptoms and physical examination can be unremarkable. Prognosis in patients with LCH of the lung is good compared with multisystem disease (only 25% will follow a progressive downhill course) [2].
Imaging features reflect histopathologic changes: earlier stages are characterised by granulomatous nodules (containing Langerhans cells); in later stages, these granulomatous nodules are replaced by fibrosis and lung cysts [2, 3].
Standard chest radiograph is performed as a routine investigation and a reticular, nodular or reticulonodular (the most common) patterns can be found. These features are better characterised by HRCT, which is now mandatory when lung LCH is suspected. HCRT initially may show only small poorly limited nodules, predominately centrilobular, often cavitating later (cheerios pattern). As the disease evolves, cystic airspaces (first thick-walled, then thin-walled) become a predominant finding: most are <10mm of size, usually have bizarre shapes and can be confluent. Nodules and cavitated nodules can resolve whereas cysts usually remain or enlarge over time. These findings are symmetrical and bilateral, predominating in the upper and middle fields. Costophrenic angles and medial tip of lingula and middle lobe can be spared. Lung volumes are normal or increased. Other features may include ground-glass attenuation and emphysematous bullae (secondary to smoke). Both pleural effusion and hilar/mediastinal adenopathy are unusual (unless caused by other coexisting diseases). Also important is to use bone window to search for bone lytic lesions.
Bronchoalveolar lavage is useful for excluding infections and other disorders but is rarely useful in the diagnosis of LCH. The final diagnosis is achieved by surgical lung biopsy at a site selected by HCRT. To date, there is no effective treatment [1-3].
There are multiple cystic lung mimickers and diseases. In individuals over 75 years old cysts can be found as a normal variant – presbyteric lung [4]; the lack of distinct walls and the occasional presence of a central centrilobular artery suggest emphysema. Honeycombing refers to thick-walled, rounded cysts arranged in several layers with loss of lung volume**; thick-walled, clustered cysts with air-fluid levels should be recognised as cystic bronchiectasis. A short differential diagnosis for cyst lung pathology should be kept in mind: lymphangioleiomyomatosis (women of childbearing age; pneumotorax, unilateral pleural effusion or pulmonary venous hypertension; innumerable, round-shaped, thinned-walled and evenly-distributed cysts, not sparing the costophrenic angles); tuberous sclerous (CT lung features identical to lymphangioleiomyomatosis; seizures, mental retardation and adenoma sebaceum; no sex predilection); LIP/collagen-vascular disease, particularly Sjögren disease (ground glass opacity; isolated or diffuse cysts admixed with nodules), as well as neurofibromatosis, DIP, subacute hypersensitivity pneumonitis, traumatic lacerations, Birt Hogg Dubé syndrome, light chain disease and neoplastic lesions, like pulmonary metastases (squamous/adenocarcinoma).