Review Question - QID 107801

This patient in this vignette demonstrates a constellation of findings related to the complications of hypomagnesemia. Although alcohol withdrawal may present with seizures, the constellation of brisk DTRs, weakness, and prolonged QT suggest hypomagnesemia. The treatment for this patient will be multi-faceted, with magnesium repletion a necessity.

Hypomagnesemia (<1.5 mg/dL) is a potentially serious condition that may be difficult to recognize due to non-specific manifestations. Mild signs of hypomagnesemia include: generalized weakness, fatigue, nausea and vomiting. As deficiency progresses patients may complain of numbness, cramping, and dysphagia. Physical exam findings may reveal increased DTRs and fasciculations. If hypomagnesemia is acute in onset and/or severe, patients may develop altered mental status, seizures, or cardiac conduction abnormalities. Low magnesium levels also have the potential to affect other electrolyte levels. In patients with hypomagnesemia it is not uncommon to see hypokalemia (K+ conductance changes increasing renal losses) and hypocalcemia (due to PTH resistance).

Jahen-Dechent et al. review the causes and treatment of hypomagnesemia. This common nutritional deficiency may be seen in many situations, which include: malnourished patients, chronic alcoholics, diabetics, patients on medications such as loop diuretics, specific antibiotics or proton pump inhibitors, and patients with prolonged diarrhea. Treatment of hypomagnesemia is usually oral magnesium therapy. Intravenous magnesium administration is indicated if the patient has severe symptoms such as seizures or arrhythmias.

Long et al. discusses the interplay between magnesium and alcoholism. Alcohol consumption increases the loss of magnesium in the urine and decreases the uptake in the liver. Low levels of hepatic magnesium are a risk factor for cirrhosis. Alcoholics are frequently malnourished, which predisposes them to magnesium deficiency.

Illustration A shows an EKG of a patient with a prolonged QT interval.

Incorrect Answers:
Answer 1: This patient is likely hypokalemic secondary to hypomagnesemia. In fact, hypokalemia may contribute to the EKG findings. If the patient is solely hypokalemic, without any other electrolyte disturbances, DTRs will be decreased rather than increased.
Answer 2: A patient with hypocalcemia may present in the same fashion as this patient (altered mental status, seizures, increased DTRs and prolonged QT). While hypomagnesemia can lead to hypocalcemia, it is important to understand that a deficiency in magnesium itself can independently cause neuromuscular abnormalities. Seeing as this patient is malnourished and a chronic alcoholic, magnesium deficiency is the likely etiology.
Answer 3: Folate deficiency is common in chronic alcoholics. It typically presents with macrocytic anemia without neurological complications.
Answer 5: Vitamin D deficiency is often asymptomatic, but may present with signs of osteomalacia in adults and rickets in children.