1- HRCT findings of progressive systemic sclerosis
HRCT findings of interstitial fibrosis in progressive systemic sclerosis are similar to those of idiopathic pulmonary fibrosis (IPF),
including ground-glass opacity,
consolidation,
fine reticular opacities,
coarse or irregular reticulation,
traction bronchiectasis and honeycombing.
Abnormalities typically show a subpleural and lower lobe predominance and often involve the lung periphery in a concentric fashion (Fig.
1).
As with the other collagen diseases,
there is a tendency for scleroderma to show a finger reticular pattern that is typical of IPF,
and also honeycombing but in a lesser manner.
On the contrary,
ground glass opacity is more common than with IPF (Fig.
2).
The HRCT appearance may reflect the histological pattern present.
Ground glass opacity is due to NSIP.
Relative subpleural sparing,
as sometimes seen in patients with RA,
may reflect NSIP.
Consolidation may indicate NSIP or OP/BOOP.
Reticulation,
traction bronchiectasis,
or honeycombing may indicate fibrotic NSIP or UIP.
Other findings are asymptomatic oesophageal dilatation present in 40% to 80% of cases (Fig.
2 and 3),
enlarged mediastinal lymph node in 60% and pleural effusion or thickening in 35%.
2- HRCT findings of pneumoconiosis
Pneumoconiosis is a broad group of lung diseases due to dust inhalation.
There are almost as many diseases of this kind as different dusts.
Silicosis,
the most frequent occupational lung disease in the world,
is the pneumoconiosis related to the inhalation of dust containing silica and it is the inhalational lung disease that concerns this work.
The earliest findings of silicosis are small well-circumscribed nodules usually measuring 2-5mm,
mainly in upper and posterior lung zones and generally with a centrilobular and subpleural distribution on the HRCT (Fig 4).
Calcification of the nodules may be visible in 10 to 20% of the cases.
With progression of the disease,
nodules can conglomerate and produce large opacities also known as conglomerate mases,
first seen in the midportion and periphery of upper lung zones (Fig.
5).
Silicosis is one of the most frequent cases of pulmonary parenchymal bands. Other findings are enlarged mediastinal and hilar lymph node in 30 to 40% of the cases,
and are frequently calcified.
Characteristic peripheral eggshell calcification is seen in approximately 5% of all silicosis cases (Fig.
6).
The diagnosis of silicosis requires the combination of an appropriate history of exposure and characteristic findings on chest image studies.
3- Synchronic scleroderma and pneumoconiosis
The HRCT appearance of scleroderma,
as it was already told,
is similar to those of IPF: a reticular interstitial pattern,
thinner than in the IPF,
that also tends to subpleural and basal fibrosis.
To these findings may be added interstitial nodules predominant in upper lung zones,
with a tendency to calcify and to congregate into conglomerate masses that progress to fibrosis,
findings that must give the clue to a synchronic inhalation disorder.
Both illnesses associate enlarged mediastinal and hilar lymph nodes.
Lymphadenopathies are more frequently seen on scleroderma (fig.
7),
but calcified lymph nodes are more characteristic of silicosis,
mainly with the periphery calcification known as eggshell calcification pattern,
highly suggestive of silicosis.
On the contrary,
one characteristic feature of scleroderma is the asymptomatic oesophageal dilatation.
Figure 8 illustrates a case of scleroderma with thoracic involvement visible on its HRTC thorax study as basal ground glass and oesophageal dilatation.
In the same patient,
interstitial nodules and eggshell calcification nodes were incidentally found,
suggesting concomitant silicosis,
later confirmed with a meticulous anamnesis.
Although a normal radiography doesn’t dismiss thoracic affectation,
both illnesses can show pathological thorax radiography.
In consequence,
the study HRCT is indicated in suspicion of any of these diseases,
even with normal thorax radiography.
The thorax radiographies in figure 9 and 10 give examples of the distribution of each sickness,
scleroderma with an interstitial pattern predominant in lower and peripheral lung zones,
and silicosis in the upper and central zones.