Overview
This Cureus case report documents a 69-year-old woman in Oman who presented with chronic abdominal pain, muscle aches, fatigue, and bloating lasting over one year. Elevated whole blood mercury was detected during a check-up in Thailand (38.72 µg/L; reference range <15 µg/L). Dietary history identified daily consumption of dried shark, shrimp, and fresh tuna as her primary protein source. Blood mercury fell to 24.36 µg/L on repeat testing in Oman 26 days later and declined further to 11.88 µg/L (below the reference threshold) 35 days after dietary modification, without chelation therapy. The case establishes a clear exposure-to-clinical-effect-to-resolution trajectory and demonstrates that dried shark can deliver clinically significant methylmercury exposure. The paper is a case report (n=1) and provides no food concentration measurements; it is classified evidence tier B for context rather than A for occurrence data.
This paper does not contain measured food concentration data. It is included on the salted-fish and shark pages as clinical evidence for the mercury exposure pathway from habitual dried fish consumption and as a source of the referenced mean mercury concentration in Omani dried shark (0.23 mg/kg, cited from Al-Mughairi et al. 2013, reference [2] in the paper; not measured in the case report itself).
Key clinical numbers
| Day | Measurement | Result |
|---|---|---|
| Day 1 (Thailand) | Whole blood mercury | 38.72 µg/L (reference <15 µg/L) |
| Day 1 (Thailand) | Arsenic | 10.8 µg/L (reference <10 µg/L) |
| Day 26 (Oman ED presentation) | Whole blood mercury | 24.36 µg/L (reference <15 µg/L) |
| Day 26 | Whole blood lead | 1.2 µg/dL (reference <30 µg/dL) |
| Day 26 | Arsenic | 3.4 µg/L (reference <10 µg/L) |
| Day 61 (after dietary change) | Whole blood mercury | 11.88 µg/L (reference <15 µg/L) |
| Day 61 | Urinary mercury | 0.82 µg/L (reference <10 µg/L) |
Routine blood count, renal and liver function tests, and bone profile were within normal limits throughout. Neurological examination was normal. Resolution of fatigue and muscle aches followed dietary modification (cessation of dried shark and limiting other seafood to 3x/week).
Referenced food concentration (not measured in this paper)
The paper cites Al-Mughairi et al. 2013 (J Food Sci 78:1082-1090, DOI 10.1111/1750-3841.12151) for the statement that “dried shark are among the highest mercury-contaminated seafood, with mean reported mercury concentrations of 0.23 mg/kg.” This is a secondary citation from an Omani seafood survey, not a measurement in the current case report. It is recorded here for traceability; the primary evidence for mercury in dried/salted fish food concentrations in the HMI library comes from other sources (alghabshi2018-oman-salted-dry-fish-metals, which measured mercury (Hg) in Omani dry shark at 0.63 mg/kg wet weight).
Toxicological context
Blood mercury reference range is <15 µg/L for adults not occupationally exposed. The patient’s initial whole blood mercury (38.72 µg/L) was approximately 2.6x the reference ceiling. Chelation therapy is typically indicated for severe symptomatic toxicity or markedly elevated levels; in this case, conservative dietary management achieved normalization. The route of exposure (methylmercury from fish muscle) is consistent with the lipophilic bioaccumulation of methylmercury in predatory fish muscle tissue. Sharks, as apex predators with long lifespans, are well-documented high-mercury fish; this case illustrates clinical translation of that food-chain accumulation in a non-occupational, dietary setting.
Methods (brief)
Whole blood mercury measured at Thai clinical laboratory (Day 1) and Central Public Health Laboratories, Oman (Days 26, 61). Urinary mercury at Day 61. Blood arsenic at Days 1 and 26. Whole blood lead at Day 26. No food samples measured in this paper. Ethics approval: Royal Hospital Ethical Committee, MOH/CSR/CR/26/16.
Evidence fitness
Case report (n=1); cannot establish population prevalence or dose-response. Provides strong individual-level mechanistic evidence (dietary cessation followed by declining mercury levels). The initial arsenic elevation (10.8 µg/L at Day 1, normalized at Day 26 to 3.4 µg/L) is noted but not considered clinically significant in the paper. Non-dietary mercury sources were not systematically excluded. The paper explicitly acknowledges these limitations. As a clinical case, it is a Class B evidence source (exposure context) rather than Class A occurrence data. The paper was peer-reviewed and published in a Springer Nature journal (Cureus) under CC BY. Use this source only for clinical context and exposure plausibility; do not use it for food concentration values.
Related evidence
- Salted fish
- Shark
- Fish
- Mercury
- Microbiological, chemical and nutritional quality and safety of salted cured fishery products from traditional dry fish processing plants in the Sultanate of Oman
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