Patient identification: 60-year old Caucasian male

Chief Complaint (CC): “Doc, I’ve been having some trouble breathing.”

1. Create a differential diagnosis based on the information provided so far. List the differential by organ system.

Differential Diagnosis for Shortness of Breath (SOB) also known as Dyspnea:

1. Pulmonary:

• COPD (emphysema and/or chronic bronchitis)
• Asthma
• Pulmonary Embolism
• Interstitial Lung Disease/Pulmonary Fibrosis
• Pneumothorax

2. Cardiovascular:

• CHF
• MI
• CAD

3. Infectious/other:

• URI or allergies
• Pneumonia
• Deconditioning

HPI:  The pt presents with shortness of breath that has slowly been getting worse over the past few years. He states he does not have much dyspnea at rest. He reports he becomes very short of breath with exertion and has to stop his activities. He states he is a farmer in central Illinois and so, this shortness of breath has become a very large problem for him. He states most of his work is strenuous and if he cannot farm, he will have no source of income. He states he has had a “hacking cough” over the past year or so that his PCP has been unable to find a cause for. He reports that there are no aggravating or relieving factors besides activity and rest, respectively. He also acknowledges that there is no correlation between shortness of breath and time of day. He denies fever, chills, night sweats, or weight loss. He denies chest pain, orthopnea, or paroxysmal nocturnal dyspnea. He also denies a productive cough and trauma to the chest or back. He denies any headaches, dizziness, syncope, visual changes, hearing changes, changes in muscle strength/tone, and difficulty walking. He denies any changes in bowel or urinary habits.

Physical exam:

General: Patient is in no acute distress. He is alert and oriented x3.

Skin: No apparent lacerations or bruises. No spider angiomatas noted.

HEENT: Head is normocephalic and atraumatic. Extraocular movements intact (EOMI). Pupils equally round and reactive to light (PERRL). Visual acuity 20/20 with corrective lenses. Ear canals patent and non-erythematous. Tympanic membranes pearly gray with no pus or air-fluid level visible.

Cardiac: Regular rate and rhythm. S1/S2 heart sound present. No murmurs, rubs, or gallops. PMI located in the 5th intercostal space in the mid-axillary line. No JVD noted.

Pulmonary: Chest expands symmetrically on inspiration. Chest wall non-tender to palpation. Resonant to percussion in all lung fields. Normal fremitus in all lung fields. Airways clear to auscultation. Diaphragmatic excursion symmetric.

Gastrointestinal: A 8cm scar is located in the lower right quadrant. Normal bounds sounds in all four quadrants. No renal, aortic, or iliac bruits noted on auscultation. No tenderness to palpation.

Musculoskeletal: Muscle strength rated as 5/5 in all muscle groups.

Neurological: Cranial nerves II-XII intact. Reflexes 2+ in all extremities.

Medications: Lisinopril, Hydrochlorothiazide, Atorvastatin, Metformin, Aspirin, Albuterol

PMHx:

• Well-controlled hypertension
• Hyperlipidemia
• Well-controlled diabetes mellitus type II

Social Hx:

• 45 pack-year history of smoking

2. What are the top 3 diagnoses you are considering? Provide evidence for each diagnosis from history and physical exam. List tests you would want to conduct. Pick from your differential diagnosis above and support with information.

Top 3 Diagnoses

All cardiovascular causes are ruled out due to the patient's lack of chest pain.

I.  Interstitial Lung Disease/Pulmonary Fibrosis

• Evidence from Hx: gradual onset of dyspnea worse with exertion, symptoms have no correlation to time of day, chronic “hacking cough” of previously unknown cause that is non-productive, farming career involves exposure to potential agricultural and environmental external aggravating factors
•  Evidence from PE: normal findings on pulmonary exam cannot rule out pulmonary fibrosis but can likely rule out pneumonia, absence of barreled chest, absence of wheezing, and absence of impaired muscle function that can sometimes be present with COPD.

II.  COPD (emphysema and/or chronic bronchitis)

• Evidence from Hx: gradual onset of dyspnea worse with exertion, chronic “hacking cough”, older age (60 years old) and 45 pack year history
•  Evidence from PE: normal findings on pulmonary exam cannot necessarily rule out COPD but can likely rule out pneumonia 

III. Asthma

• Evidence from Hx: dyspnea worse with exertion
• Evidence from PE: absence of wheezing indicates that patient's dsypnea is not likely due to asthma, but patient does have albuterol listed as a medication, will need to conduct testing in order to rule out asthma

The tests I would like to conduct next include a PFT (pulmonary function test) with spirometry, a pulsOx measurement and a CT of the chest, preferably a high resolution CT.  If a chest CT was not immediately possible due to insurance reasons or other reasons, I would order a chest XR prior to ordering a chest CT. 

3. As part of your work-up, you had ordered a pulmonary function test, which is displayed below. His FEV1/FVC is 0.91. Does the patient have normal lung function, a restrictive lung pattern, or an obstructive lung pattern?

The PFT below demonstrates a restrictive lung pattern (see Figures 1 and 2). Furthermore, the x-axis having a maximum of 4 L indicates that the patient's total lung capacity (TLC) is much lower than the normal ~5-6 L.

Figure 1. Patient's PFT. 

4. Based on the graph above, what other abnormality would you expect on this patient’s PFTs?

Although the patient's FEV1/FVC ratio is in the upper-normal range, I would expect both the FEV1 and FVC to be below normal (see Figure 3). Normal FEV1/FVC values range from 71 to 85%. In this case, the patient's ratio is actually slightly above normal, likely due to decreased lung compliance. The patient's FEV1 and FVC values are likely below normal due to a decreased ability to expire air from the lunrom this point forward, I would order an Arterial Blood Gas (ABG) analysis and determine the Alveolar-arterial oxygen difference (A-aDO₂₎ to analyze the effectiveness of O₂ diffusion across the blood-air interface within the lungs. 

Figure 3. Comparison of FEV1 and FVC in normal lungs (red), restrictive diseases (yellow) and obstructive diseases (blue). 

5. Because of his PFT, you order a high resolution CT scan of his lungs to get a better picture of the patient’s lungs. What is the final diagnosis?

The patient is diagnosed with pulmonary fibrosis as per the high resolution chest CT and the patient's PFT results. Figure 4 below demonstrates how the patient's lungs (top image) compare to normal, healthy lung tissue (bottom image). The patient's CT scan reveals a characteristic finding of pulmonary fibrosis known as "honeycombing": the appearance of trapped spaces of air within the lungs. The expanded extensions of grey and white coloration represent fibrotic lung tissue as compared to normal, healthy lung tissue.

Figure 4. High resolution CT of patient's lungs (top image) compared to a control CT of normal, healthy lung tissue (bottom image). 

6.  What are the causes of pulmonary fibrosis?

Oftentimes, the cause of pulmonary fibrosis is unknown, in which case it is referred to as idiopathic pulmonary fibrosis or IPF (see figure 5). It is estimated that approximately 10 to 15% of individuals with IPF have actually inherited familial pulmonary fibrosis (FPF). When the cause of pulmonary fibrosis is known, if often falls into one of the following categories:

Autoimmune diseases

• Certain autoimmune conditions involve the immune system attacking the patient's lungs, resulting in inflammation and scarring/fibrosis of the lungs. Examples of autoimmune diseases that can cause pulmonary fibrosis include rheumatoid arthritis, systemic sclerosis and certain muscle diseases. 

Occupational and environmental exposures

• Patients can develop pulmonary fibrosis after significant exposure to a variety of inorganic and organic dusts, including asbestos, coal dust, hard metal dusts, animal proteins, bacteria, and molds. Exposure to radiation can also contribute to the risk of pulmonary fibrosis.

Drug Induced or Medication exposures

Certain medications have been associated with development of pulmonary fibrosis.These medications include nitrofurantoin, sulfasalazine, amiodarone, propanolol, phenytoin, methotrexate, bleomycin, and oxaliplatin. 

Figure 5. Lung damage caused by idiopathic pulmonary fibrosis (IPF). 

Fibrotic, or scarred, lungs have severe damage to both the bronchioles and alveoli (see video below). This damage causes a characteristic “honeycombing” appearance on radiographs (see Figure 4 above) due to clustered spaces of air in the lungs. The scarred lung tissue in pulmonary fibrosis prevents proper gas exchange at the air-blood interface within the lungs. This decrease in gas exchange leads to lower oxygen and higher carbon dioxide content in the blood. Furthermore, the stiff fibrotic lungs inhibit proper expansion and recoil of the lungs. In conclusion, pulmonary fibrosis results in dyspnea and decreased oxygen delivery to tissues. 

https://www.youtube.com/watch?v=WzPOqbV9mFM

References

Mosenifar, Zab. “Chronic Obstructive Pulmonary Disease (COPD).” 30 Oct. 2015. Accessed via web on (11/16/15) at http://emedicine.medscape.com/article/297664-overview.

“What is Chronic Obstructive Pulmonary Disease (COPD).” Feb. 2015. Accessed via web on (11/16/15) at http://www.thoracic.org/copd-guidelines/for-patients/what-is-chronic-obstructive-pulmonary-disease-copd.php

Schwartzstein, Richard M. “Patient information: Shortness of breath (dyspnea) (Beyond the Basics).” 22 Jan. 2014. Accessed via web on (11/16/15) at http://www.uptodate.com/contents/shortness-of-breath-dyspnea-beyond-the-basics

Mayo Clinic Staff. “Interstitial Lung Disease.” 11 June 2015. Accessed via web on (11/16/15) at http://www.mayoclinic.org/diseases-conditions/interstitial-lung-disease/basics/definition/con-20024481

“The Respiratory System.” Accessed via web on 11/16/15 at https://courses.candelalearning.com/biologymajors/chapter/chapter39-the-respiratory-system/

Barreiro, Timothy J and Irene Perillo. “An Approach to Interpreting Spirometry.” 1 Mar 2004. Accessed via web on 11/16/15 at http://www.aafp.org/afp/2004/0301/p1107.html

“Pulmonary Fibrosis Foundation”. 2015. Accessed via web on 11/16/15 at http://www.pulmonaryfibrosis.org/home.

“What is Idiopathic Pulmonary Fibrosis?” Accessed via web on 11/16/15 at https://www.lungsandyou.com/ipf/what_is_ipf