Case #25: Foot Drop
Author: Michael Gottlieb, MD
Peer Reviewer: Christopher Lim, MD
A 74 year old female with a past medical history of hypertension and hyperlipidemia presents with progressive right foot weakness for the past 3 days. She states that over the past few days, she has had increasingly difficulty walking because her right foot seems to always drag while she walks. She denies any other focal areas of weakness and has no sensory loss. Her review of systems is significant for generalized weakness with diffuse muscle aches over the past year, as well as decreased appetite and constipation. She currently takes hydrochlorothiazide and lovastatin. She does not smoke, drink, or use herbal medications or illicit drugs. She is currently retired, but volunteers at a ceramic pottery shop three days/week. The physical exam is significant for a thin, elderly female, who appears pale and has a right foot drop.
Vitals: Temp: 98.4, HR: 82, RR: 8, BP: 118/76, O2 Sat: 97% on RA
What is the most likely etiology of this patient’s presentation?
This patient presents with some of the classic signs and symptoms of chronic
Lead poisoning – likely from being exposed to Lead-glazed pottery where she works.
Common sources of Lead exposure include: soldering, battery reclamation, bronzing, glass making, munitions factories, paint stripping old houses (pre-1974), drinking/making “moonshine” whiskey, pottery, and auto mechanics.
What other clinical symptoms might you expect to see with this patient?
General: Fatigue, Anorexia, Malaise
Cardiovascular: HTN, Myocarditis
Pulmonary: Pulmonary Interstitial Fibrosis
GI: Abdominal Colic, Constipation
GU: AKI/CKD, Fanconi Syndrome, Decreased Libido, Impotence
MSK: Myalgias, Arthralgias
Neurologic: Tremor, Wrist/Foot Drop (without sensory deficits), Irritability, Seizures, Encephalopathy, and Developmental Delays in Children
Hematologic: Anemia, Basophilic Stippling (rare and non-specific)
Note: Acute toxicity tends to present with abdominal pain, hepatitis, and encephalopathy.
What is the initial treatment for this patient?
Asymptomatic Children (BLL (Blood Lead Level): 45-70 mcg/dL):
-Succimer
Asymptomatic Adults (BLL: 70-100 mcg/dL):
-Succimer
Symptomatic (NOT Encephalopathic) or BLL greater than above values:
-Calcium EDTA +/- Dimercaprol OR Succimer
Encephalopathy:
-Dimercaprol + Calcium EDTA
Antidotes:
1. Dimercaprol (AKA: BAL; British Anti-Lewisite):
-Used for Lead, Mercury, and Arsenic poisoning
-Crosses the Blood-Brain Barrier
-Dose: 3-4 mg/kg IM Q 4 Hours x 5 days
-Note: Contains Peanut Oil (Use with CAUTION in peanut allergies)
2.Calcium EDTA (Edetate Disodium Acid):
-Used for Lead poisoning
-Dose: 1000-1500 mg/m2 IV Q24H (continuous infusion) x 5 days (started 4 hours after Dimercaprol)
3. Succimer (AKA: DMSA; Dimercaptosuccinic Acid):
-Used for Lead, Mercury, and Arsenic poisoning
-First line for mild toxicity due to limited side effects and PO availability
-Dose: 10 mg/kg PO Q 8 hours x 5 days, followed by 10 mg/kg Q 12 hours for 14 days
What further work-up is required?
Diagnosis of Lead toxicity is
primarily clinical. However, a BLL is helpful for deciding treatment in asymptomatic patients. In chronic cases, consider a Free Erythrocyte Protoporphyrin (FEP) or Zinc Erythrocyte Protoporphyrin (ZEP) level, which will demonstrate the burden of metabolically active lead, rather than the whole body level.
Consider radiographic evaluation for any retained Lead requiring decontamination. This may entail whole bowel irrigation for ingestions or surgical removal from bones and joints.
What is the disposition of these patients?
First, ensure that the source of Lead toxicity is removed and that family members/other exposures are also evaluated. Hospital admission is recommended for children with BLL > 70 mcg/dL, adults with BLL > 100 mcg/dL, or any patient with neurologic symptoms.
References:
Blanusa M, Varnai VM, Piasek M, et al. Chelators as antidotes of metal toxicity: therapeutic and experimental aspects. Curr Med Chem. 2005;12(23):2771-94.
Gracia RC, Snodgrass WR. Lead toxicity and chelation therapy. Am J Health Syst Pharm. 2007 Jan 1;64(1):45-53.
Patrick L. Lead toxicity, a review of the literature. Part 1: Exposure, evaluation, and treatment. Altern Med Rev. 2006 Mar;11(1):2-22.
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