Hypokalemic Periodic Paralysis: This condition is characterized by episodes of muscle weakness or paralysis, often triggered by low potassium levels. The severe hand cramping and significantly low potassium level (1.9) make this diagnosis highly plausible.

Hypokalemia due to Gastrointestinal Loss: Prolonged vomiting, diarrhea, or the use of certain laxatives can lead to significant potassium loss, resulting in hypokalemia and muscle cramping.
Renal Potassium Wasting: Certain kidney disorders or the use of diuretics can cause excessive potassium loss through the urine, leading to hypokalemia and associated symptoms like muscle cramping.
Alkalosis: Metabolic or respiratory alkalosis can lead to a shift of potassium into cells, causing hypokalemia and potentially severe muscle cramping.

Rhabdomyolysis: Although less likely, severe hypokalemia can lead to muscle breakdown (rhabdomyolysis), which is a medical emergency. Early recognition and treatment are crucial to prevent serious complications.
Cardiac Arrhythmias: Severe hypokalemia can predispose to potentially life-threatening cardiac arrhythmias. While not directly causing hand cramping, the risk of arrhythmias makes this a critical consideration.

Barium Poisoning: Barium can cause severe hypokalemia by blocking potassium channels, leading to muscle weakness and cramping. This is a rare cause but should be considered in the appropriate clinical context.
Familial Hypokalemic Periodic Paralysis: A genetic disorder that affects potassium channels, leading to episodes of muscle weakness or paralysis. This diagnosis would be considered if there's a family history or if other causes of hypokalemia are ruled out.
Gitelman Syndrome or Bartter Syndrome: Rare genetic disorders affecting the kidneys' ability to reabsorb potassium, leading to hypokalemia. These conditions are typically diagnosed in childhood but could be considered in the differential diagnosis of unexplained hypokalemia.