Nejm 1999;340:1377; 1984;311:1539

Cause:Unknown; precipitated by salicylates during chickenpox or influenza/URI (Nejm 1985;313:849)

Pathophys:Perhaps a mitochondrial dysfunction; some cases may be a urea cycle defect

In US, 555 cases/yr in 1980, now very rare, <40 with shift away from aspirin use

Sx:H/o URI, varicella, or influenza A or B 5-6 d before, or salicylate use (in 15/31). Acute onset, recurrent vomiting with mental status changes (encephalopathy)

Si:Grade I: sleepy but respond

Grade II: stuporous

Grade III to IV: increasing obtundation to coma

Grade I’s survive; 10% of grade II’s progress; grade III’s and IV’s die

r/o other inborn metabolic disorders by liver bx

Lab:

Chem:Elevated ammonia level 100 µgm %, protime >3 s prolonged predict progression, ALT and AST; bilirubin normal; glucose low

CSF:Normal except for elevated pressures

Path:Liver bx is diagnostic, shows lipid droplets, decreased succinic acid dehydrogenase, and smashed mitochondria; on EM, SER proliferation

Rx:

D₁₀ 1/2 S with K⁺ at 1500 cc/m²/d to replete volume and liver glycogen stores; vitamin K