A patient with a history of alcohol abuse presents with weakness, fatigue, and difficulty concentrating. Laboratory tests show an elevated mean corpuscular volume (MCV) and low vitamin B-12 levels. What type of anemia is likely present?

A. While a decreased residual volume can occur in restrictive lung disease, it is not the defining diagnostic criterion used to differentiate it from obstructive patterns. The FVC and TLC reductions are the primary indicators of a loss of lung compliance or thoracic expansion. RV changes are variable and depend on the specific underlying etiology of the restriction.

B. A decreased FEV1/FVC ratio is the hallmark of obstructive lung diseases, such as asthma or chronic obstructive pulmonary disease. In these conditions, air trapping leads to a disproportionate reduction in expiratory flow compared to volume. This ratio indicates an increased resistance to airflow, which is the physiological opposite of pure restrictive lung disease.

C. In restrictive lung disease, the FEV1 and FVC both decrease proportionally, which results in a normal or even slightly elevated ratio. This occurs because the lung tissue is stiff or the chest wall movement is limited, but the airways remain patent. This pattern confirms that the primary pathology involves reduced lung volumes rather than airway obstruction.

D. Restrictive lung disease is fundamentally defined by a reduction in total lung capacity below the 80 percent predicted value. A normal TLC would effectively rule out a restrictive diagnosis, as it indicates the lungs can still achieve their full physiological volume. Identifying a normal TLC suggests that any reduction in FVC is likely due to other factors.

A. Vitamin C deficiency: Scurvy, or vitamin C deficiency, typically manifests as capillary fragility leading to petechiae, ecchymosis, and friable, bleeding gums. While it can cause systemic weakness, it does not typically produce the classic beefy red tongue associated with megaloblastic changes. This deficiency primarily impacts collagen synthesis rather than the maturation of rapidly dividing epithelial and hematologic cells.

B. Iron deficiency anemia: This condition characterized by microcytic, hypochromic erythrocytes often presents with fatigue and pica, but the lingual signs are different. Patients with low iron usually exhibit glossitis characterized by a pale, smooth, or atrophic tongue rather than a sore, red one. The shortness of breath is common to all anemias, but the specific lingual inflammation points elsewhere.

C. Vitamin B-12 deficiency: Cobalamin deficiency impairs DNA synthesis, leading to megaloblastic anemia and the characteristic inflammation of the tongue known as Hunter's glossitis. The sore, red tongue results from the atrophy of lingual papillae and underlying mucosal inflammation. This deficiency also accounts for the decreased oxygen-carrying capacity that causes fatigue, weakness, and exertional dyspnea in affected patients.

D. Folate deficiency: Although folate deficiency also causes megaloblastic anemia and can result in glossitis, it is less commonly associated with the severe, painful red tongue seen in B-12 deficiency. Furthermore, folate deficiency lacks the neurologic complications that often accompany cobalamin issues. In clinical examinations, the combination of these specific systemic and lingual symptoms most strongly suggests a lack of vitamin B-12.