Metalic
prosthesis or occupational exposure are potential sources of systemic
cobalt and
chromium ion toxicity. The resultant multisystemic clinical presentation can lead to unnecessary investigations before a final etiologic diagnosis is made; with an average delay of a year or more commonly noted. A 58-year old man presented with
cardiomyopathy,
pericardial effusion, polycytaemia,
polyneuropathy,
visual impairment,
sudden hearing loss and
hypothyroidism over a 2-year period post a
metal-on-
polyethylene hip replacement surgery. Biochemistry test results showed serum
lactate of 3.8 mmol/L (0.5-2.2 mmol/L). Urine organic
acid screen showed mild increases in excretion of tricarboxylic acid cycle intermediates and 2-ethylhydracryllate; suggestive of primary or secondary
mitochondrial dysfunction. There were also slight increases in excretion of 4-hydroxyphenyllactate and
4-hydroxyphenylpyruvate suggestive of
liver dysfunction.
Acylcarnitine profile showed slight increase in
hydroxybutyrylcarnitine and tetradeceneoylcarnitine that may reflect
ketosis. In view of his clinical presentation and abnormal metabolic investigations, the initial working diagnosis was
mitochondrial disease. Subsequently, patient presented with hip
pain, and radiologic and imaging studies revealed high density collections lateral to the right proximal part of the femur, and medial to the right ilium with signal changes suggestive of metallic content. This prompted toxicology screen which revealed elevated plasma
cobalt concentration (903.32 μg/L; reference range: 0.1-0.4) and
chromium (71.32 μg/L; <0.5). Six months post right
hip prosthesis removal the concentrations have declined and was 61.72 μg/L and
chromium 23.97 μg/L. Patient felt some improvement symptomatically, without evident deterioration in his vision or hearing. This case emphasises careful consideration of past medical history, in patients presenting with multisystemic disease suggestive of
mitochondrial dysfunction, and potential causality related to exposure to toxic agents. In retrospect, the absence of a family history could be viewed as a pertinent negative finding. Not uncommonly, specialist focus on their favored system and may not search for a unifying diagnosis. It is likely further delays in diagnosis would have occurred had the patient not developed hip pains, and ultimately referred to the orthopedic surgeons more familiar with similar cases.