Pneumonia in patients with SCD can be particularly severe and has come to be called acute chest syndrome. ACS is a common cause of morbidity in SCD patients and is the most common cause of death in SCD. Multiple factors are involved in the severity of acute pulmonary injury in SCD. Nitric oxide has a multitude of related functions, many of which could impact favorably on ACS in SCD. Nitric oxide is an important inflammatory mediator which is produced by the conversion of L-arginine to citrulline by nitric oxide synthase. Nitric oxide and its precursor, arginine, are known to be low in SCD patients with ACS, suggesting that therapies, such as arginine, aimed at increasing nitric oxide production will improve the clinical course of ACS. Patients will receive 1 of 3 doses of arginine hydrochloride orally 3 times a day for 3 days while hospitalized. The efficacy of arginine will be measured by the increase in nitric oxide production and the physiological effects will be assessed.

Inclusion criteria:

• Diagnosis of sickle cell disease (Hb SS, SC, or Sbeta thalassemia)

Acute chest syndrome with the following:

• New pulmonary infiltrate on chest radiography involving a full segment of the lung and 1 of the following:
• Fever
• Cough, tachypnea, retractions, rales, or wheezing
• Chest pain

Exclusion criteria:

• Inability to take or tolerate oral medications
• Hepatic dysfunction (SGPT greater than 2 times normal)
• Renal dysfunction (creatinine greater than 2 times normal)
• Mental status or neurological changes
• Allergy to arginine
• History of priapism
• Pregnancy