A 29-year-old woman presents with a history of progressive cough and low-grade fever over the last 10 days.
e) Neurofibromatosis (von Recklinghausen’s disease)
The chest x-ray reveals numerous discrete rounded mass lesions projected over both lungs, simulating multiple pulmonary nodules. However, closer inspection will reveal that similar nodules are present outside the region of the aerated lungs, best seen in the supraclavicular locations on Fig. 1, in keeping with numerous dermal nodules and masses (in this case neurofibromas.) For patients with neurofibromatosis and numerous skin nodules who present with lung/chest symptoms, often a CT scan is required to better assess the lung parenchyma, since true lung nodules and masses can be hidden behind the myriad of skin tumours present.
Neurofibromatosis (NF) is an autosomal dominant genetically transmitted disease, with variable penetrance. The disease affects nerve cells and melanocytes throughout the body. There are two main forms of the disease, NF1 (involving chromosome 17q) and NF2 (chromosome 22q). NF1 is manifested by multiple dermal neurofibromas, groin and axillary freckling, scattered dermal café-au-lait spots (brown smooth pigmented skin patches), optic nerve gliomas, Lisch nodules (pigmented hamartomas of the iris, which appear like freckles in that location) and variable skeletal malformations. NF2 is exhibited classically by bilateral acoustic neuromas (8th cranial nerve), which can lead to headache, imbalance, tinnitus, sensorineural hearing loss and occasional paralysis. Other cerebral and spinal tumours may develop as well. There is a third condition that can present, known as Schwannomatosis (mutations in both chromosomes 17 & 22) where the patient suffers numerous Schwannoma tumours, which can develop on cranial, spinal or even peripheral nerves. The patient presented suffered with NF1. The presentation of cough and low-grade fever was chalked up to a non-specific viral URTI.
Patients with NF1 are at increased risk for developing malignant tumours (especially malignant peripheral nerve sheath tumours, which is the main cause of mortality in these patients). Both MRI and CT are excellent modalities for assessing tumour presence, location and extent, but are unreliable for accurately characterizing a tumour as benign or malignant. In such cases, FDG PET scanning is emerging as the imaging modality of choice, where available, for detecting malignant transformation in a nerve sheath tumour, for pre-op staging of the whole body extent, and for guiding biopsy procedures.
The diagnoses of both multiple pulmonary metastases and multiple pulmonary hamartomas are certainly both possible; however, these would not be the most likely, considering that similar nodules are evident overlying the lungs and outside the lung confines as well, as described above. In addition, the patient’s young age would make mets highly unlikely, unless she had a known history of prior malignancy. Hamartomas commonly are also associated with internal calcification and/or fatty tissue content (lucent on CXR). Pulmonary tuberculosis can present as multiple pulmonary nodules (tuberculomas) but this presentation is very uncommon. Primary TB usually develops in children, presenting as hilar adenopathy, with or without lung infiltrates (air space disease). Reactivation TB (usually in adults) commonly presents as consolidation in the upper lobes or superior segments of the lower lobes. Cavitation, the imaging hallmark of reactivation TB, is present is 20-45%. In “miliary TB” innumerable tiny (2-3 mm) nodules are present in both lungs, similar in appearance to millet seed, hence the name. Lung bullae represent areas of lung tissue destruction resulting in large air-filled cavities that lead to reduced gas exchange and pulmonary function. These are most commonly seen in association with emphysema but can develop congenitally and in combination with numerous other lung disorders. Lung bullae, by definition, will appear more radiolucent (dark) on CXR, since they represent pockets of dead air space. The image presented revealed numerous radiopaque nodules projected over the lungs, and as such this diagnosis should not be considered.
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