BRITISH JOURNAL OF RHEUMATOLOGY VOL. XXXI NO. 11 as having SLE (1986-1989) at this hospital, no thrombophlebitis has been observed (unpublished). The frequency of post-operative thrombophlebitis in the Chinese is rare compared with Caucasians (unpublished data). Hence, thrombophlebitis as a risk factor for developing RVT is not valid in Chinese patients with SLE. Since RVT is potentially a treatable disease early diagnosis is very important. Clinicians should be aware that Chinese patients with SLE complaining of flank pain and/or haematuria associated with high titre aCL may have RVT. Thrombophlebitis is rare in the Chinese. WEI-HSING LIU, JOUNG-LIANG LAN, DER-YUAN CHEN, HONG-LIN WEI, NING-SHEN LAI
FIG. 1.—Angiogram of left kidney: occlusion of left renal vein (arrowhead) and engorged collateral ovarian vein (arrows).
(2.8 g/d), highly elevated IgG aCL (310U/ml) (Medical Innovations Kit, Australia) and slightly raised IgM aCL (4.4U/ml). A renal biopsy showed WHO class 4 lupus nephritis. A renal angiogram revealed left renal vein thrombosis (Fig. 1). Both renal arteries and right renal vein were patent. RVT in SLE is rare  and its pathogenesis is unknown. RVT may be a complication of hypercoagulability due to nephrotic syndrome (NS) instead of SLE itself . Antecedent thrombophlebitis is considered to be a high risk factor for developing RVT in SLE patients indicating factors other than NS may also contribute to RVT . The frequency of thrombophlebitis in SLE is between 10-12% in Caucasians and is considered as a manifestation of active disease . In 375 consecutive patients diagnosed
1. Harris EN. A reassessment of the antiphospholipid syndrome. J Rheumatol 1990,17:733-5. 2. Bowels CA. Vasculopathy associated with the antiphospholipid antibody syndrome. Rheum Dis Clin North Am 1990; 16:471-90. 3. Sammaritano LR , Gharavi AE, Lockshin MD. Antiphospholipid antibody syndrome: immunologic and clinical aspects. Semin Arthritis Rheum 1990;20:81-96. 4. Wing-Hung Leung, Kee-Lam Wong, Chu-Pak Lau, et al. Association between antiphospholipid antibodies and cardiac abnormalities in patients with systemic lupus erythematosus. Am J Med 1990;89:411-19. 5. Toshiro T, Sumio F. Incidence and significance of intrarenal vasculopathies in patients with SLE. Human Pathol 1985; 16:43-9. 6. Appel GB, Williams GS, Meltzer JI, etal. Renal vein thrombosis, nephrotic syndrome, and SLE. Ann Int Med 1976; 85:310-7. 7. Gregorio M, Eduardo AV, Gaspar GE, et al. Renal vein thrombosis and inferior vena cava thrombosis in SLE. Arthritis Rheum 1984;27:539-44. 8. Peck B, Hoffman GS, Frank NA. Thrombophlebitis in SLE. JAMA 1978;1728-30.
'Snake Oil' SIR—Your journal recently published a letter on the subject of fatty acids in capsules of 'snake oil' purchased in Thailand . A conclusion was drawn that this oil was as satisfactory a source of long-chain omega-3 fatty acids as thefishoil product MaxEPA. I regret that there must have been a misrepresentation of the contents of the capsules as there is little doubt that this is a fish oil produced commercially from the Japanese sardine Sardinops melanosticta, although it could also be derived from menhaden (Tyrannis brevoortia) oil . Table I shows the reported partial fatty acid composition of the capsule contents and similar data from two analyses of the sardine oil [3,4]. These compositions are typical of many encapsulated fish
TABLE I PARTIAL FATTY ACID COMPOSITIONS (%) OF THAI 'SNAKE OIL', JAPANESE SARDINE OILS, MENHADEN OIL AND DEPOT FAT OF A TERRESTRIAL REPTILE
Thai snake oil Linoleic acid (18:2n-6) Y-Linoleic acid (18:3n-6) a-Linoleic acid (18:3n-3) Eicosenoic acid (20:1) Arachidonic acid (20:4n-6) Eicosapentaenoic acid (20:5n-3) Docosahexaenoic acid (22:6n-3) ND, not determined.
1.3  0.7 0.8 3.8 0.5 16.2 7.8
Japanese sardine oils 0.85  0.47 0.40 3.7 1.3 17.0 10.1
0.92  0.15 0.78 2.6 1.2 13.7 9.3
New Zealand US menhaden oil lizard depot fat 1.1  ND 1.1 1.3 0.6 14.6 7.5
7.6  ND 6.7 ND 1.8 1.4 5.1
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Department of Allergy, Immunology and Rheumatology, Taichung Veteran General Hospital, No. 160, Section 3, Chung-Kon Road, Taichung, Taiwan, R.O.C. Accepted 7 July 1992
LETTERS TO THE EDITOR oil products other than MaxEPA [6-8]. Since annual production of sardine oil is over 500 000 tonnes it is not surprising that some should turn up in oil capsules under other labels. Small differences in fish oil compositions are common [2,9,10] but in this case there is little doubt that the reported oil  is a fish oil. Table I includes the fat from a New Zealand lizard to show the much higher content of 18:2n-6 and 18:3n-3 typical of terrestrial animal fats [5,11], and a genuine snake oil should show a similar fatty acid composition. The authors of the letter  published in your journal correctly outline the biochemistry and benefits which might be attributed to the 'omega-3' fatty acids of their published fatty acid composition, as drawn from a large literature [12,13], but the reputation of 'snake oil' continues to be as dubious as ever! R. G. ACKMAN
1. Lau C, Gallacher C, Ross P, Belch J. Rheumatoid arthritis: Fish oil? or snake oil? Br J Rheumatol 1991;30:72-3. 2. Ackman RG, Ratnayake WMN, Olsson B. The 'basic' fatty acid composition of Atlantic fish oils: Potential similarities useful for enrichment of polyunsaturated fatty acids by urea complexation. J Am Oil Chem Soc 1988;65:136-8. 3. Ando Y, Ota T, Takagi T. 16:n(n-l) and 16:3(n-4) fatty acids in Japanese sardine oil. Proceedings of Session Lectures and Scientific Presentations on ISF-JOCS World Congress 1988, Vol II, The Japan Oil Chemists' Society. 1989; pp. 1263-8. 4. Ackman RG. Marine lipids. In: Brooker SG, Renwick A, Hanaan SF, Eyres L, eds. Fats for the future. Auckland: Duromark Publishing, 1983; pp. 2-9, 15. 5. Ackman RG, MacPherson EJ, O'DorRK. Fatty acids of the depot fats from the blue-banded seasnake (Laticauda colubrina) and its principal food the conger eel (Conger cinerus). Comp Biochem Physiol 1991;98B:423-5. 6. Sagredos AN. Fatty acid composition offishoil capsules. Fat Sci Technol 1991;93:184-91. 7. Shukla VKS, Perkins EG. The presence of oxidative polymeric materials in encapsulated fish oils. Lipids 1991,26:23-6. 8. CheeKM,GongJX,GoodReesCMefa/. Fatty acid content of marine oil capsules. Lipids 1990;25:523-8. 9. Ackman RG. The year of the fish oils. Chem and Ind 1988; March 17: 139-45. 10. Ackman RG. Fatty acid composition offish oils. In: Barlow SM, Stansby ME, eds. Nutritional evaluation of long-chain fatty acids infishoils. London: Academic Press, 1982, 25-88. 11. Hilditch TP, Williams PN. The chemical constitution of natural fats, 4th edn. London: Chapman & Hall, 1964. 12. van de Kamp J, Jackson SJ. Health benefits of fish oils. Current Bibliographies in Medicine, No. 89-7. Bethesda, MD: National Library of Medicine, 1989. 13. van de Kamp J. Fish oils. Current Bibliographies in Medicine, No. 90-8. Bethesda, MD: National Library of Medicine, 1989.
This letter was shown to Dr Lau and colleagues who reply. SIR—Dr Ackman's suggestion that Thai 'snake oil' capsules contain fish oil does not now surprise us. The scientist (PR) comments on the similarity of the two oils noting that fish, in cold water, are more likely to need polyunsaturated fatty acids than a land-based tropical or sub-tropical species. The Thais also market fish oil independently as a health tonic and as a remedy for rheumatoid arthritis, and one must suppose that it is cheaper to mislabel than to catch snakes! Thus whilst eating capsules labelled 'snake oil' may be as beneficial as fish oil, it is likely that Dr Ackman's sur-
mise is correct. We apologize for speaking with a forked tongue on this occasion! J. J. F. BELCH, P. Ross, C. S. LAU Ninewells Hospital and Medical School, Dundee DD1 9YS Accepted 20 June 1992 Extracorporeal Photochemotherapy SIR—Extracorporeal photochemotherapy (ECP) is used mainly for the treatment of cutaneous T cell lymphoma. Some recent reports have indicated its possible application for the management of auto-immune diseases [1,2]. We have conducted a pilot study on seven patients with active rheumatoid arthritis. The disease was typical and sero-positive (mean evolution 10 years). The patients (five women, two men) were over 50 years with a mean age of 68 years. They were treated with non-steroidal antiinflammatory drugs and prednisone 10 mg or less per day with a previous trial of at least two disease-modifying drugs. The treatment schedule consisted of eight ECPs performed over 3 weeks as follows: 1. Leukocytes were collected using the spectra cell separator (Cobe Laboratories, Denver, CO, USA). This technique provides a mononuclear cells (MNC) enriched product, with reduced red cell contamination (haematocrit