DHA Medical Knowledge 5 — Questions and Answers
Question 1: A 45-year-old male with type 2 diabetes presents with a painless, non-healing ulcer on the plantar surface of his right foot. He has diminished sensation bilaterally. Which pathophysiological mechanism is MOST responsible for the ulcer formation?
- Peripheral arterial occlusive disease reducing blood flow
- Peripheral neuropathy leading to repetitive unnoticed trauma (Correct answer)
- Venous insufficiency causing chronic edema and skin breakdown
- Immune suppression from hyperglycemia impairing wound healing
Correct answer: Peripheral neuropathy leading to repetitive unnoticed trauma
Peripheral neuropathy is the primary mechanism in diabetic foot ulcers. Loss of protective sensation means the patient cannot feel repeated minor trauma (pressure, friction), leading to tissue breakdown. While vascular disease and impaired immunity are contributing factors, neuropathy is the dominant cause of plantar ulcers in diabetics.
Question 2: A 28-year-old woman presents with episodes of palpitations, sweating, and anxiety that last 10–15 minutes and resolve spontaneously. Her blood pressure during an episode is 200/110 mmHg. Urine metanephrines are markedly elevated. Which of the following is the MOST likely diagnosis?
- Primary hyperaldosteronism
- Pheochromocytoma (Correct answer)
- Carcinoid syndrome
- Graves' disease
Correct answer: Pheochromocytoma
Pheochromocytoma is a catecholamine-secreting tumor of the adrenal medulla. It classically presents with episodic hypertension, headache, sweating, and palpitations. Elevated urine metanephrines (catecholamine metabolites) are the hallmark biochemical finding. Primary hyperaldosteronism causes sustained hypertension with hypokalemia. Carcinoid causes flushing and diarrhea. Graves' disease causes sustained thyroid hyperfunction.
Question 3: A 65-year-old man with a history of COPD presents with worsening dyspnea, productive cough with green sputum, and fever. His SpO2 is 88% on room air. Which organism is the MOST common cause of acute exacerbation of COPD requiring hospitalization?
- Pseudomonas aeruginosa
- Haemophilus influenzae (Correct answer)
- Streptococcus pneumoniae
- Moraxella catarrhalis
Correct answer: Haemophilus influenzae
Haemophilus influenzae (non-typeable) is the most commonly identified bacterial pathogen in acute exacerbations of COPD overall, colonizing the airways and triggering inflammatory exacerbations. Streptococcus pneumoniae is second most common. Pseudomonas is more relevant in severe COPD with structural lung disease. Moraxella catarrhalis is a less frequent but recognized cause.
Question 4: A neonate born at 34 weeks gestation develops grunting, nasal flaring, and subcostal retractions within 2 hours of birth. Chest X-ray shows a 'ground-glass' appearance with air bronchograms bilaterally. Which of the following is the MOST appropriate initial treatment?
- Systemic corticosteroids
- Intravenous broad-spectrum antibiotics
- Exogenous surfactant replacement therapy (Correct answer)
- Inhaled bronchodilators
Correct answer: Exogenous surfactant replacement therapy
The clinical and radiographic findings are classic for Infant Respiratory Distress Syndrome (IRDS/HMD), caused by surfactant deficiency in preterm lungs. Exogenous surfactant replacement (e.g., beractant, poractant alfa) given intratracheally is the cornerstone of treatment, reducing surface tension and improving alveolar stability. Antenatal corticosteroids are preventive; postnatal systemic steroids are not the primary treatment here.
Question 5: A 52-year-old woman is found to have a serum calcium of 11.8 mg/dL on routine labs. She is asymptomatic. PTH is elevated at 95 pg/mL (normal 10–65). Renal function is normal. Which of the following is the MOST likely etiology?
- Malignancy-associated hypercalcemia via PTHrP secretion
- Primary hyperparathyroidism due to a parathyroid adenoma (Correct answer)
- Vitamin D toxicity from excessive supplementation
- Granulomatous disease such as sarcoidosis
Correct answer: Primary hyperparathyroidism due to a parathyroid adenoma
Simultaneously elevated calcium AND elevated PTH points to primary hyperparathyroidism, most commonly from a benign parathyroid adenoma (~85% of cases). In malignancy-related hypercalcemia, PTH is suppressed (PTHrP is elevated, not PTH). Vitamin D toxicity and granulomatous disease also suppress PTH due to the normal feedback mechanism.
Question 6: A 38-year-old man presents with ascending weakness that started in his legs 2 weeks after a gastrointestinal illness. On examination, he has areflexia and mild distal sensory loss. CSF analysis shows elevated protein with normal cell count (albuminocytologic dissociation). Which of the following is the MOST likely diagnosis?
- Multiple sclerosis relapse
- Guillain-Barré syndrome (Correct answer)
- Myasthenia gravis
- Botulism
Correct answer: Guillain-Barré syndrome
Guillain-Barré syndrome (GBS) is an acute inflammatory demyelinating polyneuropathy typically triggered by a preceding infection. It presents with ascending flaccid paralysis, areflexia, and mild sensory changes. The hallmark CSF finding is albuminocytologic dissociation — elevated protein with few or no white cells — distinguishing it from infectious meningitis. MS does not cause areflexia; myasthenia gravis causes fatigable weakness with normal reflexes; botulism is a descending paralysis.
DHA Medical Knowledge 5
A 45-year-old male with type 2 diabetes presents with a painless, non-healing ulcer on the plantar surface of his right foot.
He has diminished sensation bilaterally.
Which pathophysiological mechanism is MOST responsible for the ulcer formation?