CASE 11638 Published on 30.03.2014

Respiratory failure in a patient with McCune-Albright Syndrome

Section

Chest imaging

Case Type

Clinical Cases

Authors

Fabiano S, Ciancarella P, Bindi A, Funel V, Liberto V, Simonetti G

Policlinico Tor Vergata
Viale Oxford 81,
00133 Roma,
Università degli studi di Roma 2 Tor Vergata;
Via Giovanni Sinchetto 76
00127 Roma, Italy;
Email:paolociancarella@hotmail.it
Patient

33 years, male

Categories
Area of Interest Musculoskeletal system, Thoracic wall ; Imaging Technique CT
Clinical History
A 33-year-old male patient with a previous diagnosis of McCune-Albright syndrome (MAS) presented with respiratory distress that limited his daily activities. His medical history included hyperprolactinaemia due to pituitary adenoma, several previous fractures of the extremities and reconstructive surgery for craniofacial deformities.
Imaging Findings
Physical examination showed the characteristic signs of MAS with extensive facial and extremities bone deformities, cafè au lait cutaneous spots, walking difficulty and dyspnoea.
Blood gas analysis demonstrated a mild respiratory acidosis, hypoxaemia and hypercapnia.
Cardiological evaluation presented a chronic pulmonary heart disease with dilatation of right cardiac ventricle and atrium, right ventricular dysfunction and pulmonary artery hypertension.
Chest plain radiography showed severe deformity of the chest wall due to abnormal proliferation of soft tissues with the involvement of ribs, both clavicles and humerus, enlargement of cardiac silhouette with severe decrease of lung volumes.
A computed tomography (CT) examination with multiplanar and volume rendering reconstructions demonstrated diffuse developmental anomalies of chest bone components, characterized by abnormal hypodense fibrous tissue associated with diffuse thinning of bone cortex, which compressed the lung parenchyma and reduced its volume as a result. Pleural effusion was also present at the bases. No lung consolidations were seen.
Discussion
MAS is a genetic, non-inheritable disease characterized by the association of polyostotic fibrous dysplasia (FD), cafè au lait spots (typically located on the same side as the bone lesions) and endocrine dysfunctions [1, 2]. It represents less than 5% of patients with FD, while the monostotic form represents 60% of patients with FD. The prevalence of FD and MAS is unknown, but it has been estimated around 1 in 30,000. MAS is ten times more common in women [3].
MAS is caused by a somatic postzygotic mis-sense mutation in the GNAS1 gene encoding the subunit of the signal-transducing G-protein.
This mutation generates autonomous fibroblast proliferation, defective osteoblast differentiation, increased bone resorption and hormonal hypersecretion, responsible for corresponding clinical features [4].
Endocrine tumours may coexist and include pituitary, adrenal, testicular, thyroid localizations [5].
Bone involvement in MAS is typically polyostotic. Upper and lower extremities are commonly affected together with pelvis and craniofacial locations, but every bone segment may be involved. Lesions expand typically from the medulla to the cortex and the surrounding cortical bone is thinned. Calcifications can be observed if a nucleus of cartilage is present.
Radiological findings depend on the degree of ossification of bone lesions, showing an increased bone radiolucency in plain radiography, well demonstrated with CT as a mild density abnormal tissue replacing bone marrow, associated with reduction of bone cortex.
The deep remodelling of woven bone and the development of abnormal tissue with poor mechanical strength cause several complications. Bone pain, usually spontaneous or after a mild trauma, often represents the first symptom of FD and MAS and reveals the presence of a pathological complete or incomplete fracture.
Malignant degeneration is rare. The most common malignancy, in order of frequency, is osteosarcoma followed by fibrosarcoma and chondrosarcoma [6, 7]. In these cases CT and MRI are necessary to confirm clinical diagnosis.
Medical therapy includes the use of bisphosphonates to improve function, decrease pain, and lower fracture risk. Surgery is indicated for confirmatory biopsy, correction of bone deformity, prevention of pathologic fracture, and eradication of symptomatic lesions [8, 9].
The involvement of ribs and chest cage is not rare in patient with MAS, but the development of respiratory failure with a restrictive pattern, pulmonary heart disease and right ventricular failure have been described only in few cases in the literature [10 -12]. In these patients surgical resection should be performed to relieve respiratory failure and improve quality of life [10, 11].
Differential Diagnosis List
Respiratory failure due to restrictive lung disease in MAS
Simple polyostotic fibrous dysplasia
Neurofibromatosis type I
Enchondromatosis
Paget disease
Final Diagnosis
Respiratory failure due to restrictive lung disease in MAS
Case information
URL: https://www.eurorad.org/case/11638
DOI: 10.1594/EURORAD/CASE.11638
ISSN: 1563-4086