COMPUTERS IN FAMILY PRACTICE

Computer Diagnosis of Skin Disease

Brian Potter, MD, and Salve G. Ronan, MD Michigan City, Indiana, and Chicago, Illinois

A transferable computer program for the differential diagnosis of diseases of the skin, CLINDERM, has been produced for use by physicians on standard IBM and compat­ ible personal microcomputers. This program lists the differential diagnosis and defini­ tive diagnosis of any presented disease of the skin, except single tumors. The physi­ cian operator indicates the distribution and detailed description of , which the interactive system integrates with a comprehensive knowledge base. The computer diagnosis in 129 cases was compared with independent interpreta­ tion of the same information by an academic dermatologist. Results were synony­ mous in 66.7% of all diseases and similar in an additional 4.7%. A common differen­ tial diagnosis was obtained in 24%, for a 95.3% rate of synonymous, similar, or common differential diagnoses. Diagnosis was different in 3.9% and description was inadequate for diagnosis in 0.8%. The variation in diagnosis showed that some descriptive terms are prejudicial of certain diagnoses; that diagnostic terms are not all completely standardized; that some diagnoses are variants of another disease; and that drug-induced eruptions simulate many other diseases. A skin disease can usually be diagnosed by specific description. Most lesions that are not diagnostic from inspection are nodular. A computer can be programmed to list diagnoses according to morphologic description J Fam Pract 1990; 30:201-210.

functional, transferable computer software system examination may, however, be excessively complex. Ob­ Afor the differential diagnosis of diseases of the skin, jectivity is improved by recording specific features ac­ called CLINDERM,* has been produced for use by phy­ cording to sets of standardized criteria. This information sicians on standard International Business Machines can then be analyzed. (IBM) and compatible personal microcomputers. The pro­ Such a process can be programmed; in other words, gram will list the differential diagnosis and render a defin­ any logical procedure can be stated as a series of instruc­ itive diagnosis of any disease of the skin except single tions to a computer. A procedure must be formulated tumors. It is of considerable assistance in clinical decision explicitly, however, in order to be programmed. making and can provide a reliable, systematic differential While medical knowledge has almost always been pub­ diagnosis. lished as concepts of a disease or groups of diseases Dermatologists diagnose an eruption by the subjective involving certain systems of the body, much less of the assessment of perceived abnormalities. This assessment literature has been organized from the point of view of is then compared with the knowledge and experience in symptoms and signs leading to diagnosis. Medical knowl­ memory. The empirical data obtained from a physical edge must be arranged in this way for computer diagnosis.1 Several works on diseases of the skin have classified 'CLINDERM is available from the author at the following address: Brian Potter, MD, primary cutaneous findings in ways that lead to diagnosis 3305 Pottawattamie Trail, Michigan City, IN 46360. secondarily. These aids to diagnosis have been based on the morphology of the eruption and noneruptive lesions2; Submitted, revised, N o v e m b e r 29, 1989. the pattern of distribution, regional localization, config­

From the Department of , The Medical Group of Michigan City Pro­ uration, and morphology of lesions3; observation of the fessional Corporation, Michigan City, Indiana, and the Departments of Dermatology most prominent and other pertinent characteris­ end Pathology, The University of Illinois College o f Medicine, Chicago, Illinois. tics4; identification of the clinical pattern and prediction of Requests for reprints should be addressed to Brian Potter MD, PO Box 262, Michigan City, IN 46360. the cutaneous level of involvement5; problem-oriented

© 1990 Appleton & Lange the JOURNAL OF FAMILY PRACTICE, VOL. 30, NO. 2: 201-210, 1990 201 CLINICAL DECISION—SUPPORT SYSTEMS

algorithms starting with the patient’s presenting com­ plaint, signs, and symptoms^; and sequential histopath- ological analysis.1 Previous systems for computer diagnosis of diseases of the skin have recently been reviewed.9

THE CLINDERM SYSTEM

First, in creating the CLINDERM program, all the prin­ cipal and characteristic diseases of the skin were resolved into several common, elementary cutaneous forms. These elementary forms represent the primary lesions, which are monomorphous by definition. The lesions reflect the limited number of ways in which the skin can respond to a pathologic stimulus. Although lesions can occur inde­ pendently—for instance, a —they are typically multiple and compose the eruption, or . An eruption is composed of individual lesions that exist for variable periods of time. One eruption can be distin­ tables to be about 80%.10 The diagnosis of basal cell guished from another by the morphology and the distri­ epithelioma from clinical examination is correct in only bution of the lesions. An eruption may be either mono­ 56% to 73% of cases.11 A clinical, gross, morphological morphous or polymorphous. diagnosis of and obviously cannot Lesions constitute a second general category of cuta­ be made with certainty. neous pathologic processes, namely, the noneruptive dis­ After the specialized information has been incorporated orders of the skin, hair, nails, and mucous membrane. into the computer memory, this knowledge and experi­ Noneruptive disorders include discoloration, hypertro­ ence can be applied to individual cases. The second class phy, , and degeneration, all of which may be of of data required to reach a diagnosis is an adequate de­ indefinite duration. scription of the abnormality exhibited by the patient, Any eruption or noneruptive disorder of the integument There must be a procedure to collect this information. can be characterized by the distribution on the skin, , Contemplation of the algorithmic nature of computer , or mucous membrane and by the combination of programs suggests that the optimal method of computer lesions exhibited. In this way a logical description of the diagnosis should take advantage of the branching charac diseases of the skin was listed in a comprehensive knowl­ teristic of machine languages. By selections from the edge base and organized into a formal representation of knowledge base on the computer screen, the physician cutaneous medicine. can indicate a complete description of the eruption. The The name of a disease may occur several times in the process leads through a relevant sequence until the diag­ knowledge base and within different sets of differential nosis is reached. diagnosis, because a disease may become manifest in CLINDERM is the functioning system utilized to gen­ several fashions, for instance, both macular and scaly, or erate the differential diagnosis and to ensure that none has either localized or extensive. The number of different been overlooked. The indications for the use of the sys­ diseases in the knowledge base is 548, but the total num­ tem are to list the differential diagnoses and render the ber of all the diagnoses in the system is 1256. To reach any definitive diagnosis of diseases of the skin. In its applica­ diagnosis requires a maximum of 9 nodes to be passed tion in a medical setting, the process is interactive. The through. physician represents the interface between the appear­ The CLINDERM system can accept any case pre­ ance of the patient and the computerized knowledge base sented for diagnosis and will allocate each case to a dis­ To illustrate the procedure, a photograph of an eruption ease class. Multiple nodular lesions that occur in the form is shown in Figure 1. The abnormality is of the skin, so of an eruption have been included, but individual tumors “ on the skin” would be chosen from the first display on have been excluded because such nodular lesions require the computer screen (Figure 2, left). This selection causes and histopathologic interpretation for definitive the computer to take two actions: first, to place this line in diagnosis. Previous studies have shown the accuracy of its temporary memory in an array of phrases descriptive clinical diagnosis of common skin tumors from criteria of this patient: and second, to display a list of primary

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lesions (Figure 2, right). From this list “ macular; flat, by, “ leukodermic, achromic ” (Figure change in color of the skin” would be selected, as this 3, right). description corresponds to the abnormality shown in the The disease manifests itself in an extensive distribution. photograph. The chosen phrase is automatically added to In Figure 4, left, the corresponding line that the operator the descriptive array. selects is added to the description. If more than one The computer then displays a further list of alternative description could be applied, either or both can be chosen findings (Figure 3, left), from which “ discoloration; per­ in turn, as the diagnosis will be listed under alternative sistent, pathological ” is selected, followed specifications.

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Figure 4. The information already obtained is sufficient to include in the differential diagnosis (left). One more screen (right) is required to exclude other possible diagnosis.

The amount of information already obtained is suffi­ and the diagnosis that the phrases indicate (Figure 5, cient to include tinea versicolor in the differential diagno­ right). The operator may choose to print any or all of the sis but is insufficient to exclude other possible diagnoses. differential diagnoses. One more menu is required to do so (Figure 4, right) in The objective description and diagnosis are then com­ which each phrase is linked to the corresponding diagno­ bined with personal information. Individual features that sis in Figure 5, left. may be noted in the history or examination and a treat­ The machine now recapitulates the descriptive phrases ment plan may be added to the consultation report.

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demic dermatologist who had no prior connection with THE MEDICAL GROUP 1225 EAST COOLSPRING AVENUE the construction of the knowledge base or with the system HICHI6AN CITY, IN 46360 (219) 879-6531 design. The objective descriptive sections of the case reports were forwarded to the dermatologist, who was DERMATOLOGICAL CONSULTATION asked to write a differential diagnosis and to indicate the definitive diagnosis. The dermatologist’s interpretation NAME OF PATIENT: DATE: 0 5 - 1 7 - 1 9 8 8 was based therefore only on the age and sex of the patient COMPLAINT: l o s s o-f s k i n c o l o r DURATION: T o u r m o n t h s and the description of the disease that was compiled by OCCUPATION: l a b o r e r A6E: 3 4 the computer from the indications of the operator. FAMILY HISTORY: n o n e The first 107 cases were taken from patients in the SET: m a l e TOPICAL APPLICATIONS: v i t a m i n E c r e a m senior author’s clinical practice and included ambulatory MARITAL STATUS: s i n g l e ALLERSIES: n o n e patients and hospital consultations. All the patients pre­ FILE t i 8 8 - 1 8 2 9 CURRENT MEDICATION: n o n e sented new cases of an eruption or noneruptive lesions. REFERRAL: The patients were taken consecutively until known dupli­ HISTORY: cate diagnoses were encountered; the duplicate was then OBJECTIVE DESCRIPTION: eliminated from the study, and the next new patient was Examination o-f the patient shows that the derm atological selected. findings are on the skin; macular; fla t, change in color of the skin; discoloration; persistent, pathological When a series of over 100 patients had been accumu­ dyschromia; leukoderm ic, achromic hypopigm entation; extensive, widespread, diffuse, disseminated distribution; lated, most of the diseases being encountered were dupli­ detachable, flaking, desquamation, on upper parts of body. cates of diagnoses already included in the study. Another DIFFERENTIAL DIAGNOSIS: TINEA VERSICOLOR 22 were therefore taken from published reports of unusual or rare cases not actually seen by either of the authors. To POSTINFLAMMATORY this extent, some were patients of tertiary care facilities. The total number of individual cases was 129, with 122 DIAGNOSIS: TINEA VERSICOLOR different diagnoses. TREATMENT: Cases of patients presenting with common, recogniz­ able nodular lesions such as seborrheic keratoses, , and nevi were included in the study, as ordinarily such DATE OF REPORT: 0 5 - 1 7 - 1 9 8 3 Brian Potter, M.D. lesions would not all be submitted to biopsy. The only cases excluded from the study were those of nodular Figure 6. The report is printed automatically, utilizing the lesions considered to need a biopsy for definitive diagno­ information obtained. sis. Such lesions comprised chiefly neoplasms, granulo­ mas, and other individual nodules. The cases were not otherwise limited because the com­ The report is now printed automatically (Figure 6), puter system covers the entire domain of dermatology. using the information obtained on a form displaying the Since all cutaneous presentations can be analyzed in name and address of the office or clinic, personal data, terms of their primary lesions, any case could be accepted history taken, objective description, differential diagnosis, and a differential diagnosis given. The patients presenting definitive diagnosis, treatment plan, the date, and the with a single cutaneous tumor were eliminated, however, name of the physician. After the report has been proof­ because in these cases discriminating features are notori­ read, any typographic errors that are found may easily be ously lacking. A0 the possible diagnoses of an individual corrected. The report may be reprinted any number of tumor could conceivably be given, but such lists become times. inordinately long. The patient’s name and file number may be preserved for future reference, combined with the diagnosis, to en­ able future sorting, listing, and searching. These items are added to an archive or cumulative list of these items. RESULTS

When the computer diagnoses were compared with those METHODS of the dermatologist, they were found to be synonymous, similar, common within the differential diagnosis, or dif­ The accuracy of each computer diagnosis of 129 cases of ferent. A summary of the results of the validation is given skin diseases was validated by comparison with indepen­ in Table 1. dent interpretation of the same information by an aca- In 95.3% of the cases, the computer and the dermatol-

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TABLE 1. RESULTS OF VALIDATION TABLE 2. COMPUTER- AND DERMATOLOGIST-DETERMINED SIMILAR DIAGNOSES OF MARGINALLY Results Number Percent DIFFERENT SIGNIFICANCE Dermatologist and computer made 86 66.7 Computer Dermatologist synonymous diagnosis conglobata Cystic acne Similar diagnosis of marginally 6 4.7 different significance Atopic Lichenified chronic eczema

Common differential diagnosis 31 24.0 Blastomycosis Deep fungus infection

Dermatologist and computer made 5 3.9 Eczema different diagnoses Lichenoid purpura Purpura pigmentosa chronica Description inadequate for diagnosis 1 0.8 by dermatologist Stevens-Johnson syndrome multiforme

Total 129 100

chogryphosis, pigmented hairy , , tel- ogen effluvium, and vitiligo. ogist made a synonymous or a similar diagnosis, or pre­ In only nine of the 86 synonymous diagnoses were the sented a common differential diagnosis. More than two lesions nodular, included because biopsy was not consid­ thirds of all the skin diseases were diagnosed synony­ ered essential for diagnosis. The nine were , mously. Most of these were diseases that manifest them­ cavernous , , epidermal in­ selves with an eruption. clusion , annulare, , molluscum con- In 66.7% of all the diseases, the dermatologist’s diag­ tagiosum, , and verruca vulgaris. nosis was synonymous with that of the computer. The In six cases (Table 2) the computer’s and dermatolo­ eruptive disorders in which the dermatologist agreed with gist’s diagnoses were similar, but of marginally different the computer’s diagnosis comprised acne vulgaris, acro­ significance. For instance, the computer was programmed dermatitis continua, asteatotic dermatitis, autoeczemati- to make lichenoid purpura a specific diagnosis, while the zation reaction, bullous , , derma­ dermatologist simply indicated chronic pigmented pur­ titis herpetiformis, dermographism, diaper dermatitis, pura. The Stevens-Johnson syndrome, a specific, plurior- , disseminated superficial porokeratosis, ec­ ificial type of that involves the mu­ zema, simplex, epidermolysis bul­ cous membrane including the conjunctiva, was diagnosed losa dystrophica, erythema infectiosum, erythema multi­ specifically by the computer, but the dermatologist used forme, erythema toxicum neonatorum, exfoliative the more general term of erythema multiforme. , , herpes genitalis, , dermatitis is a specific, disseminated form of lichenifkd, herpes zoster, , insect bites, , lichen chronic eczema; contact dermatitis is another, different planus, et atrophicus, erythemato­ type, usually localized and isomorphic. Both were diag­ sus, necrolytic migratory erythema, neurodermatitis, nosed specifically by the computer, but by the dermatol­ nummular eczema, , , per­ ogist simply as eczema. leche, , polymorphous light eruption, Two of the six cases of similar diagnosis were nodular. pretibial myxedema, pseudofolliculitis barbae, , One of these was conglobate acne, a severe, cystic, ex­ , , seborrheic dermatitis, stasis tensive, chronic form of acne. The computer was pro­ dermatitis, steroid-induced purpura, telangiectasis macu- grammed to regard conglobate acne as a specific disease, laris eruptiva perstans, tinea versicolor, urticaria, vascu­ as it is rare, progressive, and occurs almost exclusively in litis, and vulvovaginitis. men. The dermatologist’s diagnosis was cystic acne. The noneruptive lesions diagnosed synonymously by In one case of ulcerated nodules, both the computer computer and dermatologist included acanthosis nigri­ and the dermatologist correctly considered the diagnosis cans, , , aplasia cutis congen­ of deep fungus infection. The dermatologist did not go ita, condyloma accuminata, dermatosis papulosa nigra, further. CLINDERM showed the diagnosis of blastomy­ epidermal nevus, giant pigmented nevus, vul­ cosis, with a differential list of specific fungus diseases. garis, pilaris, male pattern alopecia, , In 31 cases the computer and the dermatologist each myxedema, , nevus araneus, nevus de- made a differential diagnosis that included one or more pigmentosus, nevus flammeus, nevus sebaceus, ony- common diagnoses. In Table 3 the first column shows the

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definitive diagnosis that the computer was programmed to TABLE 3. COMPUTER- AND DERMATOLOGIST-DETERMINED give. The second column shows the common terms in the COMMON DIFFERENTIAL DIAGNOSIS differential diagnosis suggested by the computer and by the dermatologist. The five nodular presentations in this Definitive Diagnosis Common Differential Diagnosis category of common differential diagnosis comprised gan­ Addison’s disease glion, multicentric reticulohistiocytosis, sebaceous hyper­ Argyria plasia, verruca vulgaris, and xanthogranuloma. Ochronosis In six instances the computer and the dermatologist Hemochromatosis made a different diagnosis on the same case (Table 4). In Atopic dermatitis one case “ silvery scaling" in the description of ichthyosis inadvertently suggested psoriasis to the dermatologist. Bullous Erythema multiforme The word “” in a description led to a diagnosis of Bullous drug eruption cellulitis by the dermatologist, for ulcerative, nodular, Dermatophytosis Psoriasis indurated lesions. The computer listed cryptococcosis Eczema and other deep fungus infections. In another case the dermatologist could not make a diagnosis based on the Drug eruption Drug eruption Toxic epidermal necrolysis computer’s description. The lesions were described as Viral nodular, circumscribed, solid, indurated; superficial; nonulcerative; smooth, rounded, firm, discolored eleva­ tions. From this description, the computer was pro­ Dysplastic nevi grammed to make the diagnosis of sarcoidosis, with up to Sweet’s syndrome 10 other diagnoses in the differential diagnosis. Erythema multiforme Four of these 6 lesions, different or incapable of diag­ nosis, were nodular. The two other multiple nodular pre­ Erythema induratum gangrenosum sentations in this group were nevus and Stasis subcutaneous fat necrosis of the newborn. Factitial dermatitis Burn

Ganglion Paronychia

DISCUSSION Grover's disease Grover’s disease

Junction nevus Lentigo The question addressed in this work was whether the Junction nevus partly subjective practice of dermatological diagnosis can be converted into an objective analytic procedure, using a Larva migrans computer programmed with an extensive knowledge base Multicentric reticulohistiocytosis of specific features in sets of standardized criteria. Multicentric reticulohistiocytosis The CLINDERM system has been tested at two beta- sites by other qualified dermatologists and is believed to Mycosis fungoides be free of logical errors. The software is available com­ Nevus cell nevus mercially, but until now has been offered only to derma­ Nevus tologists who have actually operated it at national and international meetings. The senior author has a financial Psoriasis interest in the product, which is already in use at a United Onychomycosis

States Veterans Administration hospital and by several Deep fungus infection dermatologists in this country and in Europe. Pyoderma gangrenosum The algorithmic system of classification is based largely on Darier’s classic text,2 modified to eliminate the dated emphasis on syphilis, tuberculosis, , and other Rubella Viral exanthem infections then much more common but now rare. The Kawasaki syndrome numerous diseases involving the skin that have been de­ lineated since Darier’s time have been added to the knowledge base. Scabies The main difference between Darier’s categorization Scleromyxedema , disseminated and that of CLINDERM is that the latter’s categorization

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TABLE 3. (CONTINUED) TABLE 4. DIFFERENT DIAGNOSES OF SAME CASE MADE BY COMPUTER AND DERMATOLOGIST Definitive Diagnosis Common Differential Diagnosis Computer Dermatologist Sebaceous Connective tissue nevus Steroid-induced purpura Traumatic purpura Nevocytic nevus Epidermal nevus Senile purpura Fox-Fordyce disease Darier’s disease Basal cell nevus syndrome Sarcoid Sweet’s syndrome Erysipelas Lichen amyloidosus Sweet’s syndrome Cowden's syndrome Alopecia areata Tinea capitis Kyrle’s disease

Toxic epidermal necrolysis Toxic epidermal necrolysis Cryptococcosis Cellulitis Drug eruption Atypical mycobacterial infection Sporotrichosis Pyoderma gangrenosum Trichotillomania Alopecia areata Blastomycosis Tinea capitis Leishmaniasis Trichotillomania Chromomycosis Verruca vulgaris Verruca Mycetoma Lepromatous Verruca vulgaris (of nail fold) Paronychia

Xanthogranuloma Drug eruption vascular disease Toxic epidermal necrolysis Morphea Measles

Ichthyosis vulgaris Psoriasis begins with the primary lesion, whereas Darier opens Asteatosis Pityriasis lichenoiodes chronica directly with the morphology of the eruption. Other ap­ Sarcoidosis (Did not make a diagnosis) parent idiosyncracies have been avoided, such as Darter’s Seborrheic keratosis consideration of atrophy and sclerosis together. Verruca vulgaris Some of the authorities mentioned in the references Nevocytic nevus have used algorithms for parts of their subject, but in the Keloid CLINDERM classification the entire domain of dermatol­ Atypical mycobacterial infection ogy can be visualized as a tree structure. The classifica­ tion cannot be depicted explicitly on paper, however, because of physical limitations, as the number of branches Subcutaneous fat necrosis of increases exponentially, which is the reason for its adap­ newborn tation to computer memory. Connective tissue nevus To avoid problems of idiosyncratic terminology, each Generalized eruptive Hunter-Hurler syndrome use of a specialized dermatologic term is followed in the Lipid proteinosis description, where space permits, by a more general syn­ onymous phrase or definition (Figures 3 to 6). As a result, another version with different terminology should not be academic dermatologist. The diagnostic criteria were needed for use by family physicians. purely clinical and morphologic. A similar conceptual approach with a different knowl­ The patients were not followed up for the purposes of edge base has been previously employed for histopathol- the study, as the object was to compare the computer’s ogy, in TEGUMENT, a computer-assisted dermato- and dermatologist’s diagnoses with each other directly, pathologic diagnosis system. An article on this subject has rather than with laboratory tests or subsequent develop­ already been published.1 ments. For instance, direct microscopic examination of The object of the study reported here was to validate scales in potassium hydroxide solution is indicated in that the knowledge programmed into the computer in the dermatophytosis. Such cases were included in the study, form of objective description leading to diagnosis of each however, as these diseases have to be considered in the case can give rise to a similar diagnosis in the mind of an differential diagnosis before the test is made.

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When the diagnoses were not in agreement, the com­ eruption by the computer suggested a number of specific puter knowledge base had to be modified to remove inad­ diseases to the dermatologist. equate, ambiguous, or inadvertently tendentious descrip­ The knowledge base was continually upgraded by in­ tive terms. In these cases the dermatologist’s diagnosis formation from this iteration. Actions were taken to im­ was added to the differential diagnosis in the computer prove the agreement between machine and human by memory. making the descriptions more specific. The chief modifi­ In similar diagnoses of marginally different significance, cations required in the knowledge base were to avoid the dermatologist did not always distinguish between two nonspecific, vague, or biased descriptive terms and to add related diagnoses in which one is a variant of the other. the dermatologist’s diagnoses. The computer was programmed to interpret every de­ A factor limiting the diagnostic accuracy of the system scription with a specific diagnosis, while the dermatologist is the ability of the operator to translate morphologic tended to make more general diagnoses. features into the objective form expected by the com­ Some terms are not completely standardized, for in­ puter. A certain amount of skill is required in recognizing stance, eczema and dermatitis. These terms are almost synonymous, the difference between them being similar morphology. Most physicians are already trained to some to the variance between the concepts of pneumonia and extent in this subject, however, and the computer pneumonitis. Some other terms could perhaps be super­ prompts with lists of observations to be searched for in the annuated, but they are still useful to describe specific patients being examined. cutaneous findings. Many dermatological diagnoses are This process actually represents human-aided com­ descriptive, but as such they may be preferable to ep- puter diagnosis. The programmed computer may be re­ onyms, which are not even descriptive. garded as an electronic textbook, and even in the absence The computer and the dermatologist frequently consid­ of a patient, it can provide explanation and teaching. Any ered equivalent diagnostic terms in the differential diag­ number of possible variations of theoretical morphologic nosis because less information is needed to make such a description will each lead to a differential and a definitive list than to arrive at a definitive diagnosis. The computer diagnosis. The system may therefore find another use in operator, however, has an advantage over the dermatol­ continuing education. ogist of seeing on the computer screen a list of all distin­ guishing features that characterize closely related dis­ eases. The computer and dermatologist made a different diag­ CONCLUSIONS nosis in several cases because some descriptive terms were imperfect, equivocal, inadvertently misleading, or Eruptive and noneruptive diseases of the skin can usually prejudicial of a particular diagnosis in the dermatologist’s be diagnosed from their morphology or from an objective mind. description. Accordingly, a computer can be programmed Several nodular lesions were diagnosed correctly by to list differential and definitive diagnosis according to both dermatologist and machine, but they represent a specific morphologic description. small minority of the total. Including the description that Most lesions that are not diagnosable on inspection of was inadequate for diagnosis by the academician, a ma­ jority of the different diagnoses were nodular presenta­ the gross morphology are nodular. Lengthy lists of differ­ tions. The morphological description of a nodule often ential diagnosis of nodules can be given, but biopsy and cannot be made sufficiently specific for a single, definitive histopathologic interpretation are required for definitive clinical diagnosis. diagnosis of such lesions. The nodular eruption of which the dermatologist was In this study the computer and the dermatologist both unable to make a diagnosis lacked the certain critical considered equivalent terms in the differential diagnosis of minimum of information required for an objective diagno­ a number of cases because less information is needed to sis; this case is an example of an eruption of which an list possible diagnoses than to arrive at a definitive diag­ objective description is capable of more than one inter­ nosis. The computer made more definitive diagnoses be­ pretation. Such diseases can hardly be distinguished de­ cause it was programmed to make a specific diagnosis finitively by their clinical or gross morphology. A diagno­ from every different description. sis and differential diagnosis consistent with multiple The program provides the physician with the advantage nodular lesions can be listed. In all such cases, however, of seeing on the computer screen a list of all characteristic biopsy is indicated. features that distinguish closely related diseases. A drug-induced reaction can simulate almost any other The following reasons accounted for the variance in eruption.12 For this reason, the description of a drug diagnosis:

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1. Some descriptive terms are insufficient, ambiguous, 4. Lazarus GS, Goldsmith LA, Tharp MD: Diagnosis of Skin Disease inadvertently tendentious, or prejudicial of certain diag­ Philadelphia, FA Davis, 1980 noses. 5. Tharp MD, Charley MR, Gilliam JN: An analytic approach to the 2. Standardization of diagnostic terms is less than com­ diagnosis of skin diseases. In Stein JH (ed): Internal Medicine. Boston, Little, Brown, 1983, pp 999-1012 plete. 6. Kraus SJ: Evaluation and management of acute genital ulcers in 3. Certain diagnoses represent variants of other dis­ sexually active patients. Urol Clin North Am 1984; 11:155-162 eases. 7. Lamberg SI: Dermatology in Primary Care. Philadelphia, WB Saun­ 4. Drug-induced reactions can simulate many other ders, 1986 eruptions. 8. Lynch PJ: Dermatology for the House Officer, ed 2. Baltimore, Williams & Wilkins, 1987, pp 67-78 9. Stoecker WV: Computer-aided diagnosis of dermatologic disorders. Dermatol Clin 1986; 4:607-625 References 10. Vanker AD, Stoecker WV: AI/DERM: Diagnosis of skin tumors. Proceedings of the AAMSI Congress. Washington, DC, American 1. Potter B, Ronan SG: Computerized dermatopathologic diagnosis. J Association for Medical Systems and Informatics, 1984, pp 213-217 Am Acad Dermatol 1987; 17:119-131 11. Presser SE, Taylor JR: Clinical diagnostic accuracy of basal cell 2. Darier J: Textbook of Dermatology. Philadelphia & New York, Lea & . J Am Acad Dermatol 1987; 16:988-990 Febiger, 1920 12. Bruinsma W: A Guide to Drug Eruptions: A File of Side Effects to the 3. Fitzpatrick TB, Walker SA: Dermatologic Differential Diagnosis. Chi­ Skin, ed 4. Oosthuizen, Netherlands, De Zwaluw: Norwood, NJ, cago, Year Book Medical, 1962 American Overseas Book Co (distributor), 1987, pp 115-122

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