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Table 1 Diagnostic criteria for Yusho (updated)

From: Association of clinical findings in Yusho patients with serum concentrations of polychlorinated biphenyls, polychlorinated quarterphenyls and 2,3,4,7,8-pentachlorodibenzofuran more than 30 years after the poisoning event

The diagnostic criteria for Yusho were revised on October 26, 1972; supplemented on June 14, 1976; and an item related to blood polychlorinated quarterphenyl (PCQ) level was added on June 16, 1981. The study group of Yusho started to measure blood levels of dioxins in annual medical check-ups from 2001. It was considered appropriate to add an item corresponding to the blood 2,3,4,7,8-PeCDF level; therefore the criteria were supplemented and further revised on September 29, 2004.
Conditions of the incident
1. Proof that Kanemi rice bran oil contaminated with polychlorinated biphenyls (PCBs) was ingested.
2. There are also some cases in which PCB is transferred from mothers with Yusho to their children.
3. Familial occurrence is also seen in many cases.
Important manifestations
1. Acneform eruptions
Black comedones* seen on the face, buttocks and other intertriginous sites; comedones with inflammatory manifestations; and subcutaneous cysts with atheroma-like contents that tended to suppurate.
2. Pigmentation
Pigmentation of the face, palpebral conjunctivae, gingivae**, and nails etc. (including so-called 'black babies').
3. Hypersecretion of the meibomian glands.
4. Unusual composition and concentration of PCBs in the blood.
5. Abnormal level of blood PCQ
   (1) ≥ 0.1 ppb: an abnormally high concentration.
   (2) 0.03 to 0.09 ppb: the boundary between high and normal concentrations.
   (3) ≤ 0.02 ppb (detection limit): normal concentration.
6. Abnormal level of blood PeCDF
   (1) ≥ 50 pg/g lipids: an abnormally high concentration.
   (2) 30 to 50 pg/g lipids: a relatively high concentration.
   (3) < 30 pg/g lipids: normal concentration.
Standard symptoms and findings
1. Subjective symptoms
   (1) General fatigue
   (2) Headaches, dull headaches
   (3) Paresthesia of the extremities (abnormal sensation)(4) Increased eye discharge
   (5) Cough and sputum
   (6) Inconstant abdominal pain
   (7) Altered menstruation
2. Objective findings
   (1) Manifestation of bronchitis
   (2) Deformation of nails
   (3) Bursitis
   (4) Increased neutral fat in the serum
   (5) Increased serum γ-glutamyl transpeptidase (γ-GTP)
   (6) Decrease in serum bilirubin
   (7) Small-for-date baby
   (8) Growth retardation and dental abnormality (retarded eruption of permanent teeth)
  1. * Black comedones (other sites):
  2. black comedones appearing on body parts other than the face, auricle, and trunk
  3. ** Palatal findings
  4. Palatal lesions known to occur in Yusho patients include pigmentation and parakeratosis in the gingiva, dental root dysplasia, and odontatrophia.
  5. Palatal findings from examinations in Yusho patients are recorded as follows:
  6. (1) The upper teeth and lower teeth are each divided into 3 sites:
  7. site 1 = 7–4, site 2 = 3-3, and site 3 = 4–7.
  8. (2) Pigmentation patterns are divided into the following patterns recognized in Yusho patients:
  9. Condition 1 = diffuse, Condition 2 = punctate, Condition 3 = linear,
  10. Condition 4 = zonal, Condition 5 = cloudy, Condition 6 = island shaped