A 44-year-old Thai man presented with progressive dyspnea and non-productive cough for 1 month.

His underlying disease included asthma, which he had lost to follow-up for 5 years, but the disease had been well-controlled. The previous plain films of the chest during that time were within normal limits. He denied smoking, alcohol drinking, and the use of herbal supplements. 

Physical examinations:

Thickening and tightening of skin at face and upper chest wall. Poikeloderma at forehead, back, and legs. 

Coarse crepitations at both lower lung fields, without rhonchi or wheezing. 

Questionable loud P2 with pansystolic murmur at Lt mid and lower parasternal border. 

Investigations: 

Chest radiography showed newly developed scattered interstitial infiltration at both lung fields. 

CT scan of chest was then performed, and the result is shown above. 

Questions: 

1. Please describe the abnormal chest CT scan findings, name a specific sign. 

2. Please give the provisional diagnosis and the differential diagnosis. 

3. What is the proper next step plan for investigations and management? 

ANSWERs

1. Abnormal chest CT scan findings and a specific sign
CT chest with contrast (lung window axial view of a 44-year-old Thai man)
-Reticular infiltration at bilateral anterolateral upper lobe and posterosuperior lower lobe
-Honeycomb appearance at bilateral basal lung invloved subpleural areas with traction bronchiectasis 
suspected “Four corners sign”

2. Provisional diagnosis and the differential diagnosis
Provisional diagnosis : Interstitial lung disease with typical UIP pattern   
“Four corners sign” is a specific finding for ILD caused by connective tissue diseases, highly suspicious of systemic sclerosis 

Differential diagnosis : 
-Connective tissue disease : Systemic sclerosis ILD, Rheumatoid arthritis ILD, Autoimmune myositis ILD, Mixed connective tissue disease ILD, other ILDs such as vasculitis ILDs, IPAF
 
3. Next step plan for investigations and management

3.1 Plan for investigations for diagnosis

-Work up for respiratory tract infections causing mimics of ILD 
-Look for other relevant clinical findings e.g. multiple organs involvement such as myositis, non-erosive arthritis, Raynaud's phenomenon, mechanic's hands, skin rashes, sicca symptoms and constitutional symptoms
-Serological evaluation of autoimmune antibodies depended on clinical findings such as ANA, anti-scl-70, anti-centromere, myositis specific antibodies, RF

3.2 Plan for evaluation of ILD severity and complication
-Pulmonary function tests อาจพบเป็น restrictive pattern with decreased diffusing capacity for carbon monoxide (DLCO)
-6-minute walk test (6MWT)

-Baseline echocardiogram to evaluate risks of pulmonary hypertension

3.4 Plan for management

-Specific treatment:  high-dose corticosteroids, immunosuppressive therapy (cyclophosphamide, mycophenolate mofetil, azathioprine), anti-fibrotic agents (nintedanib) 

-Home oxygen therapy indication: severe chronic resting room air hypoxemia, severe exertional room air hypoxemia (desaturate to an SpO2 <88% on a 6MWT)

เรียบเรียงโดย นพ.พัฒนสรณ์ เก้าเอี้ยน แพทย์ประจำบ้านชั้นปีที่ 2 กองอายุรกรรม รพ.ภูมิพลอดุลยเดช พอ. 

Reference:  Walkoff L, White DB, Chung JH, Asante D, Cox CW. The Four Corners Sign: A Specific Imaging Feature in Differentiating Systemic Sclerosis-related Interstitial Lung Disease From Idiopathic Pulmonary Fibrosis. J Thorac Imaging. 2018 May;33(3):197-203 

Am J Respir Crit Care Med Vol 202, Iss 10, pp e121–e141, Nov 15, 2020