Benign nocturnal leg cramps: This is the most common cause of nocturnal leg cramps, often related to muscle fatigue, overuse, or poor circulation. The negative lab results support this diagnosis, as it is typically not associated with underlying systemic diseases.

Electrolyte imbalance: Although labs are negative, mild or intermittent electrolyte imbalances (e.g., magnesium, potassium, calcium) might not be captured. These imbalances can cause muscle cramping.
Medication side effects: Certain medications, such as diuretics, can lead to electrolyte imbalances or directly cause muscle cramps.
Dehydration: Inadequate fluid intake can lead to dehydration, which may cause or exacerbate muscle cramping.

Peripheral artery disease (PAD): While less likely, PAD can cause leg cramps, especially at night, due to reduced blood flow to the muscles. Missing this diagnosis could lead to severe consequences, including limb loss.
Neurological disorders: Conditions like peripheral neuropathy or radiculopathy can cause nocturnal leg cramps. These conditions require prompt diagnosis and treatment to prevent progression.
Hypothyroidism: Although labs are negative, hypothyroidism can sometimes present with muscle cramps, among other symptoms. Missing this diagnosis could lead to long-term health consequences.

Sarcoidosis: A rare condition that can cause muscle cramps, among other systemic symptoms.
Amyloidosis: A group of diseases that can lead to muscle cramps due to the deposition of abnormal proteins in muscles and nerves.
Dystonias: A group of neurological disorders that can cause involuntary muscle contractions, leading to cramps.