This is an uncommon process involving an increase of mature lymphocytes in the alveoli and interstitial spaces. This inflammation and fibrosis of the alveoli limit the ability of oxygen transfer to the capillary bed.

In the majority of cases, no specific cause can be found. However dust, aerosols, radiation, and drugs are considered to be causes of the condition. The persistent alveolitis leads to irreversible interstitial fibrosis.

Of the 180 interstitial types of lung disease, they all share common features which include: dry cough, exertional dyspnea, digital clubbing, inspiratory crackles at the base of the lungs, and hypoxemia.

Chest x-ray, computed tomography (CT) scan, fiberoptic bronchoscopy, lung biopsy, thoracoscopy, or bronchoalveolar lavage are used most commonly to diagnosis the pathology. Pulmonary function tests show reduced lung volume.

Corticosteroids have been used to treat symptoms; however, their benefits have not been proven.

The natural progression of the disease and its prognosis are not well understood. Spontaneous resolution has occurred, and corticosteroid treatment has resulted in resolution. Progression of the condition to lymphoma or respiratory insufficiency or both from pulmonary fibrosis has occurred.

• May be entitled to special monthly compensation where the Veteran has a single service-connected disability rated as 100% with additional service-connected disability or disabilities independently ratable at 60% or more, which are separate and distinct from the 100% service-connected disability and involves different anatomical segments or bodily systems. See  38 CFR 3.350(i)(1) – Special Monthly Compensation (SMC).

• Review 38 CFR 3.809a for eligibility for entitlement to Special Home Adaptation grants under 38 U.S.C. 2101(b).

• Review special provisions regarding the evaluation of specific respiratory conditions under 38 CFR 4.96(a) - Rating co-existing respiratory conditions and 38 CFR 4.96(d) - Special provisions for the application of evaluation criteria for diagnostic codes 6600, 6603, 6604, 6825–6833, and 6840–6845.