Qing Fen

Retrospective analysis of 172 patients diagnosed with mercury poisoning at a Beijing centre over six years. Renal damage occurred in 46 patients (26.7 percent); of those, 41 presented with nephrotic syndrome and 5 with isolated proteinuria, and membranous nephropathy was the dominant pathology in 18 of 35 biopsies (51.4 percent). Chelation was the mainstay of treatment with an overall effective rate of 97.5 percent. The authors emphasise that mercury nephropathy is commonly misdiagnosed and missed, which matters directly for practitioners whose patients take mercurial minerals.

Retrospective study of 288 patients with mercury poisoning treated at a Chinese military general hospital between 2014 and 2019. Chinese folk remedies were identified as one of the three principal exposure sources alongside occupational exposure and mercury-containing cosmetics. Nervous system involvement was commonest (50.3 percent), then renal (16.4 percent) and respiratory (8.0 percent); nephrotic syndrome caused by folk remedies was predominantly membranous nephropathy, and peripheral neuropathy was more frequent from folk remedies than from other exposure routes. Recovery was possible but slow, taking a mean of about 23 months for nephrotic syndrome and about 38 months for confirmed neurological injury. The authors call explicitly for improved safety surveillance of folk remedies.

Public health investigation of Californian households using imported skin creams adulterated with calomel, documenting elevated urinary mercury in users and in household members who never applied the cream, together with mercury vapour contamination of the homes themselves. It establishes that calomel is not a self-limited exposure confined to the person taking it, and that mercurous chloride in a topical preparation generates absorbable mercury in the domestic environment.

The study that identified mercury as the cause of infantile acrodynia, or pink disease. Quantitative urinary mercury was raised in the great majority of affected children, and the exposure was traced principally to calomel teething powders and calomel-containing anthelmintics. Acrodynia developed in roughly one in 500 exposed children and killed a substantial minority of those affected; the syndrome essentially disappeared after calomel was removed from teething powders in the mid-1950s. This is the definitive demonstration that mercurous chloride, the supposedly safe mercurial, causes severe and sometimes fatal mercury poisoning in children at ordinary medicinal doses.

Extended clinical and analytical series consolidating the mercury aetiology of acrodynia, correlating the syndrome with mercury exposure from calomel-containing preparations and describing the clinical picture: painful red swollen hands and feet, rash, sweating, tachycardia, hypertension, photophobia, profound irritability, anorexia, insomnia and marked proximal muscle weakness. It is the reference description of chronic mercurous chloride poisoning in children.

British clinical report linking acrodynia to mercury intake, part of the sequence of work that led to calomel being withdrawn from proprietary teething powders. It documents the dose-response problem directly: the mercurial was being given at conventional, label-recommended amounts, and the poisoning followed anyway in susceptible children.

Five biopsy-proven cases of membranous nephropathy attributable to mercury in traditional Indian medicines, with proteinuria resolving after the medicines were stopped and chelation given. The species and system differ from Chinese calomel practice, but the lesion, the mechanism and the source category are the same, and the series makes the point that mercurial nephropathy from a traditional preparation is reversible only if someone thinks to ask what the patient is taking.

Two toxicologically confirmed cases of systemic heavy-metal poisoning from mucocutaneous application of Chinese mineral medicines. In the first, a 51-year-old man applied a hong-dan mixture containing lead tetraoxide, arsenic and mercury into an anal fistula for two weeks and developed perianal gangrene, rash, anaemia, hair loss, peripheral neuropathy and muscle atrophy, with raised urine mercury and arsenic; DMPS gave only partial recovery and the neuropathy persisted four years later. The relevance to Qing Fen is direct: the external route is not a safe route, and application to damaged or infected tissue is the worst case.