1. Mysterious Rash in a Patient with Congenital Hip Dysplasia
Erin Hammett
Scripps Clinic

2. Introduction
Cobalt-chromium is a wear-resistant and high strength alloy used in metal on metal (MOM) prosthetic joint implants
Cobalt is a common allergen in contact dermatitis, when exposed to high levels this can lead to toxicity with systemic manifestations

3. Case
HPI: 45 year old Caucasian female with a past medical history of undifferentiated connective tissue disease and right sided congenital hip dysplasia s/p total hip arthroplasty (THA) in 1993 with revision in 2003
Chief complaint: Pruritic erythematous rash on upper extremities for several weeks without change in medications or new chemical contacts
Review of systems: Positive for chronic fatigue

4. Exam Findings

5. Case
Labs: Complete blood count, chemistry panel, C reactive protein and erythrocyte sedimentation rate WNL
Imaging: X Ray R hip: Increased lucency surrounding the femoral stem suggesting particle disease
Skin biopsy: Spongiotic dermatitis with a negative direct immunofluorescence
Further lab testing: Blood cobalt level 10.1 ug/L (ref <3.9 ug/L), serum chromium level 5.7 ug/L (ref <5.0 ug/L)

7. Case Diagnosis: Contact dermatitis 2/2 cobalt toxicity
Treatment: Total hip arthroplasty revision
Outcome: Rash resolved within 3 month time period

8. Follow Up Exam

9. Discussion
One million patients worldwide have MOM implants, most of which were placed between the years of
Wear debris complications in MOM implants composed of cobalt- chromium can lead to elevated serum cobalt levels
Cobalt toxicity can result in systemic symptoms such as weakness, fatigue, cognitive decline, peripheral neuropathy, hearing/visual loss, cardiomyopathy, and hypothyroidism

10. Discussion
The pathophysiology of cobalt toxicity is thought to be due to a delayed type IV hypersensitivity reaction causing aseptic loosening, osteolysis, and cutaneous reactions. The dermatitis component is due to a metal-protein complex transported to skin Langerhans cells causing subsequent T cell activation
Measurement of cobalt/chromium ions and imaging should be performed in patients with MOM implants who present with systemic symptoms or hip pain
Systemic symptoms typically improve with revision arthroplasty

11. References
1. “Wong C, Nixon R et al. Systemic Allergic Dermatitis Caused by Cobalt and Cobalt Toxicity from a Metal on Metal Hip Replacement.” Contact Dermatitis. Volume 71, No 2, 2014 pp
2. Graves SE, Rothwell A et al. “A Multinational Assessment of Metal-on-metal Bearings in Hip Replacement.” Journal of Bone and Joint Surgery, American Volume 93, No 3, 2011, pp 43-47