Deposition of membrane attack complex in cutaneous lesions of lupus erythematosus

CORRESPONDENCE A hard subject: Use of a durometer to assess skin hardness To the Editor: I greatly enjoyed the article by Falanga and Bucaloon the use of a durometer toassess skin hardness (J AM ACAD DERMATOL 1993;29:47-51). They appear to have found a simple, objective technique to help quantify the subjectivesensations on which webase our clinical judgments. By devising a method to relate the structural changes producedby a pathologic process with measurable physical properties of skin, they have augmented our abilityto assess cutaneousdisease. One thing I found curious, however, was the failure of durometer measurement to correlate with clinicalscoring on areas like the foreheadand dorsal digit. Perhaps thisrelatesto the complexity and lack of homogeneity of cutaneous structure. It may be usefulto think of skinas a multilayered solid, each layer of which has different physical properties. When one palpatesthe skingently and progressively, one encounterschangingsensations ofpressure. Thesedepend on the resistance to elastic deformation at each level of indentation and on viscous flow.' They are followed by a sensation of lessening pressure on release, the rate of which is related to elastic recoil. For example, on palpation of a keratoderma on the palm or sole, onemight perceive a crustlike sensation-an initial resistance from palpation of the thickenedstratum corneum, followed by the relativecomplianceof the dermis and underlying fat. Touching a large follicular cyst, one might feel the complianceof the epidermisand dermis, the resistanceof the cyst capsule, the "give" related to viscous flow of the cyst contents, and finally the brief, but persistent, sensation of pressure on digital retraction caused by the elasticity of the cyst wall. Durometer hardness is an empirical measurementrelated to elasticityand viscoelastic properties ofmaterials.2 The ability of palpation to provide information about these parameters at variousdepths provides a uniqueadvantage over durometer measurement. Thus by gentle palpation one can easily appreciate the softness of forehead skin as separate from that of the hard bone below. This can be perceived irrespective of the thickness ofsubcutaneous fat in this area. The inability of the durometer to measure this suggests that the force of its indentation may be toogreat to isolatethe epidermis and dermisfrom underlyinglayers.One wonders whetherdurometerswith lower or adjustable loads are available. Not only might these more accurately measure combined dermoepidermal hardness,but by focusing on hardnessof increasingly supcrficiallcvels, they might be usefulinquantifying epidermal changes caused by abnormal keratinization. The reproducible and quantitative nature of instrumental measurementmakesit wellsuitedto the testingof Journal of theAmerican Academy of Dermatology

hypotheses using the scientific method. Without it the process of discovery would be much slower. However, sometimes its limitations can serve to remind us of the amazing versatility of our own senses.

Peter L. Reisfeld, MD 4100 Duff Place Seaford, NY 11783

REFERENCES 1. Tregear RT. Force between molecules: mechanics ofskin. In: Physical functions of skin. New York: Academic Press, 1966:78-81. 2. ASTM Designation D 2240-91. From theAnnual Book of ASTM Standards. Philadelphia: American Society for Testing and Materials, February 1992.

Reply To the Editor: I thank Dr. Reisfeld for his interest and insightful comments. I agree with him that it would be desirable to develop and test a durometer with smaller adjustableloads soas to permititsusein thinareasof skin and at sitesoverlying bone.Suchaninstrumentmayprove useful for the assessment and evaluation of scars and other fibrotic conditions. For now, however, wehave focused on obtaining the most consistent results with the equipment that is presently available. We wish to report that we are obtaining even moreconsistent results, with littlevariation amongdifferent operators, by using a type 00 durometer model (Rex Gauge Co., Glenview, Ill.). This model is weighted at the top, thus minimizing the effectof different forces applied bythe operator. We concur with Dr. Reisfeld, however, that more needs to be done to make the durometer an instrumentsuitable for use in all skin areas. Vincent Falanga, MD Department of Dermatology University ofMiami School ofMedicine P.O. Box 016250 Miami, FL 33101

Deposition of membrane attack complex in cutaneous lesions of lupus erythematosus To the Editor: In their article entitled "Deposition of Membrane Attack Complex in Cutaneous Lesions of Lupus Erythematosus" (J AM ACAD DERMATOL 1993;28:687-91), Helm and Peters aver that the deposition of the membrane attack complex (MAC) is both a sensitive and specific marker for cutaneous lupuserytheSeptember, Part 1, 1994 515

Journal of the American Academy of Dermatology September 1994

516 Correspondence matosus. In their article, they described II control specimens including patients with pemphigoid, urticaria, urticarial vasculitis, eczema, relapsingpolychondritis, and a skin ulcer. With the exception of relapsingpolychondritis, none of these conditions, in our opinion, are difficult to distinguish histologically from lupus erythematosus. The two connectivetissuediseases that may be histomorphologically similar to lupus erythematosus are mixed connectivetissue disease (MCTD) and dermatomyositis, examples of which were not included in their control group. We have had an opportunity to study MAC depositionin eight casesof dermatomyositis and two casesof MCTD. Of the eight cases of dermatomyositis, five showed intense granular deposition of MAC at the dermoepidermaljunction. All eightofour patientseither had coexistent malignancies or clinical and serologic evidence of myositis, hence corroborating the diagnosis of dermatomyositis in each instance. Both MCTD case studies showedgranular keratinocyte decoration; bothshowedno deposition at the dermoepidermal junction. In addition, we studied 11 patients with subacute lupus erythematosus, all of whom had keratinocyte decoration with MAC in a fashion that mirrored the deposition of IgG in each instance. In conclusion, we do not believe that deposition of MAC at the dermoepidermal junction is specific for cutaneous lupus erythematosus. We also believe that additional patterns of epidermal stainingfor MAC are useful in the subclassification of lupus erythematosus and possibly in the diagnosis of other connective tissue diseases such as mixed connective tissuedisease. A. N. Crowson, MD, FRCP Director of Laboratories Misericordia General Hospital 99 Cornish Ave. Winnipeg, Canada R3C 1A2

C. M. Magro, MD Department ofPathology Beth Israel Hospital Harvard Medical School 3304 Brookline Dr. Boston, MA 02139

Bullous pemphigoid and autoimmune thrombocytopenia To the Editor: Taylor et al. recentlydescribed the occurrence of autoimmune thrombocytopenia in two patients with bullouspemphigoid (BP) (J AM ACAD DERMATOL 1993;29:900-2). They stated that onlyonecase of BP associated with autoimmune thrombocytopenia and au-

toimmune hemolytic anemia has previously been documented.' In their review, the authors omitted our previous report in the JOURNAL2 of a similarassociation; in one of our three patients with BP and long-standing multiple sclerosis autoimmune thrombocytopenia and hemolytic anemia alsodeveloped and wasthereforethe firstreported case associating BP and Evans' syndrome. The autoimmune thrombocytopeniadeveloped 3 years after the discontinuationof BP treatment and required systemiccorticosteroidtherapy (platelet count, 6000 cells/mrrr'). No recurrence of bullous lesions was observed. As described by Taylor et al., the autoimmune thrombocytopeniawas not related to any medication and did not parallel the course of the BP. Isabelle Masouye, MD Jean-Hilaire Saurat, MD Clinique de Dermatologie, Hbpital Cantonal Universitaire 1211 Geneve 4, Switzerland REFERENCES 1. Aoki Y, Miyake N, Yamasowa M, et al. A caseof autoimmune hemolytic anemia and bullous pemphigoid-like skin lesions combined withidiopathic thrombocytopenic purpura. Jpn J Clin HematoI1990;31:346-51. 2. MasouyeI, Schmied E, Didierjean L, et al. Bullous pemphigoidand multiplesclerosis: More than a coincidence? J AM ACAD DERMATOL 1989;21:63-8.

Reply To the Editor: We thank Drs. Masouye and Saurat for drawing our attention to their case report detailing the occurrenceofEvans'syndromein association with bullous pemphigoid (BP) and multiple sclerosis in one of their patients. In addition to the coexistence of BP and autoimmune thrombocytopenia and hemolytic anemia, there are several reports of BP in association with a variety of autoimmune diseases.'Becauseofthe presenceof anti-basement membrane zone antibodies, it might be postulatedthat BP is an autoimmune disorder.However, we recently reported the results of a large case control study, which failed to establish that there was an increasedincidence of autoimmunediseasein patients with BP.! Dr. Gayle Taylor Dr. Fenella Wojnarowska Department ofDermatology, The Churchill Hospital Oxford, tis. REFERENCE

1. Taylor G, VenningV, Wojnarowska F, et al. Bullous pemphigoid and autoimmunity. J AM ACAD DERMATOL 1993; 29:181-4.