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REVIEW ARTICLE
Year : 2022 | Volume
: 42
| Issue : 1 | Page : 1-10
Acne mimickers
Rajat Kandhari
Dr Kandhari’s Skin and Dental Clinic, New Delhi, New Delhi, India
Correspondence Address:
MD, MSC Rajat Kandhari
Dr Kandhari’s Skin and Dental Clinic, 11 Munirka Marg, Vasant Vihar, New Delhi 110057
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/ejdv.ejdv_31_21
Acne is now considered a chronic disease and may occur at any age group contrary to previous beliefs. The presentation of acne is polymorphic and can manifest as comedones, papules, pustules, nodules, cysts, sinuses, and varying kinds of scars. It may occur in varied areas of the body. Although the diagnosis of acne is rarely difficult for the dermatologist, the occurrence of acne in different age groups, the pleomorphic lesions, the varying distribution, and its association with various systemic disorders or syndromes may cause difficulties in diagnosis even for an astute clinician. Here, we review various diagnostic possibilities of acne and their differentiating characteristics.
Keywords: acne, mimickers, systemic disorders
Acne forms a major chunk of any dermatology practice, and it is said that in a lifetime a person is more likely to have acne than any other disease [1]. Acne is now considered a chronic disease and may occur at any age group contrary to previous beliefs. The presentation of acne is polymorphic and can manifest as comedones, papules, pustules, nodules, cysts, sinuses, and varying kinds of scars. It may occur on the face, chest, or back and is frequently associated with seborrhea. Rare forms of acne may lead to systemic involvement [2].
Although the diagnosis of acne is rarely difficult for the dermatologist, the occurrence of acne in different age groups, the pleomorphic lesions, the varying distribution, and its association with various systemic disorders or syndromes may cause difficulties in diagnosis even for an astute clinician [3]. Once the diagnosis of acne has been made, the lack of adequate response to appropriate treatment despite patient adherence should alert the clinician to consider the possibility of a misdiagnosis and the presence of conditions mimicking acne [3]. The list of conditions mimicking acne is summarized in [Table 1] [4]. A detailed discussion of all the enumerated conditions mimicking acne is out of the scope of this chapter, so here we discuss some of the common ‘acne mimickers.’
Conditions mimicking comedonal acne
Milia
Milia, also known as Epstein pearls [5] are small (generally <3 mm) white, benign, superficial keratinous cysts. Although, histologically milia resemble miniature infundibular cysts, clinically they closely resemble closed comedones. Primary milia that are commonly seen in infants may also occur in children and adults (benign primary milia of children and adults) and may be a common misdiagnosis for young practitioners ([Figure 1]a, b). Secondary milia, on the other hand, are not so commonly confused with comedonal acne as they usually develop post trauma to the skin, for example, burns, sunburns, dermabrasion, or in blistering disorders [6] ([Figure 1]a, b).
Figure 1 (a) Primary milia occurring close to the eye and (b) secondary milia post-dermabrasion and split thickness skin graft.There is scarcity of data on the origin of these lesions, although few studies suggest that they tend to originate from the sebaceous collar of vellus hairs (lower infundibulum), similar to comedones that originate from the pilosebaceous unit. Benign primary milia commonly occur on the cheeks, forehead, eyelids, and rarely genitalia. There is discrete lack of papules, pustules, nodules, and cysts unless the patient is suffering from coexisting acne vulgaris. Milia are persistent and may not easily respond to topical treatment and usually require simple evacuation [6].
Sebaceous hyperplasia
Hyperplasia of the sebaceous glands is a benign proliferation seen usually in adults and clinically appears as yellowish papules, 1–3 mm in diameter seen commonly on the forehead, temples and chin area. They resemble closed comedones ([Figure 2]a,b), but no keratinous material is extruded on attempted extraction, instead an oily secretion is revealed. Treatment is usually not required unless requested for cosmetic reasons and may be addressed with the help of physical treatments such as gentle cautery, cryotherapy, or trichloroacetic acid. Lasers have shown some promise in treating sebaceous hyperplasia where a carbon dioxide laser, a 1450 nm diode laser, [7] and a pulse dye laser [8] have been used with variable success. Further, sometimes the lesions may be diffuse warranting a trial of oral isotretinoin, which has proven to be of some benefit. Aminolevulinic acid photodynamic therapy has also been used for the treatment of this condition [9], but is presently not available in India.
Steatocystoma multiplex
Steatocystoma is an uncommon disorder of the pilosebaceous unit characterized by epithelial lined, sebum-filled dermal cysts with sebaceous glands in their cyst walls. Rarely solitary, this disorder may be autosomal dominant and more commonly sporadic in nature [10]. Sporadic, solitary lesions are called steatocystoma simplex. Clinically lesions are asymptomatic, yellowish papules or cysts, of varying sizes, which may rupture into the dermis and become infected and rarely result in the formation of sinus tracts. Unlike acne, lesions of steatocystoma are commonly found on the trunk, upper arms, chest, or scrotum and less commonly on the face. These lesions when incised usually express an oily material or a creamy-to-cheesy malodorous material. Asymptomatic lesions mimick closed comedones although lesions of steatocystoma that suppurate may closely resemble acne conglobata. Further, unlike acne, lesions tend to be persistent despite treatment. Simple excision or cyst drainage with removal of the cyst wall is possible particularly when there are few lesions. Numerous techniques have been described for the treatment of steatocystoma lesions [11],[12],[13], including innovative techniques such as removal with the help of a vein hook [14]. Use of carbon dioxide laser has demonstrated variable success [15]. Isotretinoin, intralesional steroids, and cryotherapy have been tried in inflamed lesions of steatocystoma [16].
Trichoepithelioma
Trichoepithelioma is a benign adnexal neoplasm. The tumor cells form rudimentary hair follicles but do not form actual hair shafts. The lesions are skin-colored, papules or nodules that are firm in consistency with a varying diameter of 2–8 mm. Commonly occurring on the face and scalp these lesions tend to be located around the nasolabial folds, nose, on the cheeks and forehead [17].
Osteoma cutis
Osteoma cutis essentially means focal ossification within the skin.
Rather than a mimicker of acne this entity is described as an uncommon complication of women with long-standing inflammatory acne and usually requires no treatment [18]. Clinically osteoma cutis lesions are persistent, 2–4 mm, skin-colored papules, which are firm to hard in consistency unlike comedones. Further they may be associated with hyperpigmentation, especially after treatment with minocycline and tetracyclines. Treatment modalities are limited. Treatment is challenging and surgical techniques such as combined dermabrasion and punch biopsy, scalpel incisions and curettage, and extirpation of the small bone fragments after microdissection seem to be most promising [19]. The firm and persistent nature of these lesions as well as lack of response to topical treatment differentiates them from closed comedones [20].
Conditions mimicking open comedones
Comedo nevus
This is a hair follicle nevus comprising a localized collection of dilated follicles filled with keratinous plugs or ‘comedo-like’ lesions. Nevus comedonicus appears typically at birth or develops during early childhood and is usually asymptomatic. The inflammatory variant of nevus comedonicus may present with repeated bacterial infections, drainage, cysts, fistulas, and abscess formation [21]. It is usually found on the face, neck, trunk, and upper extremities ([Figure 3]), but have also been reported on palms, soles, scalp, or the penis, wherein differentiation from comedonal acne becomes easy [22]. The lesions may be linear, unilateral, bilateral, blaschkoid, or dermatomal in distribution [23]. The clinical picture of comedones in a particular pattern, which are long standing and unresponsive to conventional treatment helps in clinching the diagnosis. Further histopathology reveals keratin-filled epidermal invaginations associated with atrophic sebaceous glands. Rarely nevus comedonicus may be associated with abnormalities in the central nervous system, skeletal system, skin, and eyes and is known as the nevus comedonicus syndrome. Treatment is sought for cosmetic purposes, wherein topical retinoids, 12% aqueous ammonium lactate solution, and electrocautery have shown some benefit for less severe cases [24].
Favre racouchot syndrome
Favre racouchot syndrome (Maladie de Favre et Racouchot) or Elastoidosis Cutanea Nodularis Cystica et Comedonicus is the presence of nodular elastosis, accompanied by multiple grouped giant comedones and small pilosebaceous cysts, seen around the eyes and extending to the cheeks and the temples ([Figure 4]). This syndrome is usually confined to facial skin and is bilaterally symmetrical, but unilateral and circumscribed forms have been reported [25]. This entity may be associated with other signs of chronic photodamage, which include diffusely thickened and yellowish discoloration of the affected skin particularly of the forehead and the back of neck. On the neck, it may be defined by well-defined furrows into an irregular rhomboidal pattern called cutis rhomboidalis nuchae or ‘farmer’s and ‘sailor’s skin.’ Histologically, at an early stage, the elastic fibers of the upper and middle dermis become curled and fibrillar to form thick, irregular masses. At a later stage, the elastotic degeneration becomes more diffuse, forming long swollen bands of irregular texture, with finely granular elastin and dense microfibrillar masses. There is also an increase in collagen and glycosaminoglycans, although ultimately the collagen decreases [25].
Figure 4 Elastotic changes with giant comedones and phymatous changes on the nose.Occupational acne
Occupational acne seems to be one of the most frequent causes of work-related skin disease, second only to contact dermatitis. The different forms of occupational acne are oil acne, coal-tar acne, and chloracne. Tropical acne or hydration acne is also seen in some occupations [26].
Oil or tar acne
This acneiform eruption is seen commonly in refinery and oil-field workers working in tar distillation plants and petroleum distilleries. The lesions usually occur in areas of the skin in contact with oils and crude tars. Oil acne is more common in males, is predominantly comedonal interspersed with rare inflammatory lesions, and can occur not only on the face but other body parts such as thighs and lower arms. Workers in contact with grease such as car mechanics may develop these lesions even on the lower limbs [27].
Chloracne
Chloracne dates back to 1899 when it was first identified by Herxheimer. It was later defined as the production in the human patient of a type of acne with characteristic clinical features that have been produced, so far, only by aromatic chlorinated hydrocarbons of varying structures [28]. Although less commonly seen today, clinically chloracne has a distinct presentation, wherein the areas most commonly involved are below and to the outer side of the eye and behind the ear. The lesions are predominantly comedonal and as the exposure to the toxic compounds increases the lesions may increase in number to hundreds and small, pale yellow-colored cysts also appear. Further the skin may attain a grayish hue after prolonged exposure to the chloracegens as virtually every follicle contains a comedone. Other areas such as axillae, scrotum, extremities, trunk, and buttocks are rarely involved. There are lesions that may persist for years after exposure to the causal agents [28]. Other skin lesions may also occur, including hypertrichosis and palmar and plantar hyperhidrosis. Rare systemic involvement includes fatigue, anorexia, neuropathy, impotence, disturbed liver function, and hyperlipidemia. Occupational history, unusual distribution, and the relative lack of inflammatory lesions help to distinguish this entity from acne vulgaris [28].
Tropical acne
Also known as ‘hydrating acne’ or ‘cooking acne’ this entity is commonly seen in cooks and pressers, particularly working in hot and humid conditions. Although comedones are seen in tropical acne, it is more commonly associated with the occurrence of inflammatory lesions due to the hydration of the pilosebaceous duct pores which aggravates the blockage of the duct [29].
Treatment of occupational acne is tough and lesions are fairly persistent. The removal of the source is vital, topical retinoids such as adapalene and tretinoin may help. Antibiotic therapy is useful for inflamed lesions and isotretinoin helps in oil or tar acne but is of limited use in chloracne as the sebaceous gland has already undergone atrophy. Gentle cautery may help in such cases [29].
Conditions mimicking inflammatory acne
Infections mimicking inflammatory acne
Bacterial folliculitis − the clinical appearance of bacterial folliculitis may vary depending on whether the infection is in the superficial or deep portion of the follicle. Superficial folliculitis (follicular impetigo or Bockhart) is an infection of the follicular ostium with Staphylococcus aureus. The clinical appearance is that of a domed, folliculocentric, yellow pustule, sometimes with a narrow, red areola. The pustules develop in crops and may heal within 7–10 days, but sometimes become chronic. The lesions may be associated with mild pain, tenderness, and/or pruritus. Superficial folliculitis is common due to occlusion, hyperhydration (in those working in hot/humid conditions) topical application of corticosteroids, waxing and shaving against the direction of hair growth, and in those with a nasal carriage of S. aureus. Further when the infection progresses to involve the follicle beneath the infundibulum a furuncle develops. A furuncle is a folliculocentric, painful, nodule with a central pustule that becomes necrotic [30]. Furuncles are common on the face, neck, axillae, breast, buttocks, and thighs. Recurrent furunculosis should be a warning sign for the clinician and one must rule out diabetes mellitus, chronic staphylococcus carriage, malnutrition, HIV infection, or constant triggers such as oil massages or constant occlusion. The symptoms associated with the history usually help in differentiating bacterial folliculitis from acne. Further, these lesions may not respond well to conventional anti-acne treatment, which warrants the identification of the causative organism with a bacterial culture. Superficial folliculitis that is localized usually responds to topical antibacterials such as fusidic acid, mupirocin 2%, and topical retapamulin. If the infection is widespread or recurrent, the causative trigger must be sought and treatment with oral antibiotics is warranted [30].Gram-negative folliculitis − this occurs as a complication of long-term oral or, less frequently, topical antibiotic therapy used to treat acne. Clinical features include a sudden eruption of multiple, small follicular pustules commonly localized around the perioral or perinasal regions. This results from overgrowth of Gram-negative organisms including Klebsiella, Escherichia coli, Serratia marcescens, Proteus mirabilis, or Pseudomonas aeruginosa. It is recommended to culture pustules in any patient who develops a sudden, pustular eruption and has been on long-standing oral or topical antibiotic treatment for acne. Further, Gram-negative organisms may not always be recoverable from each pustule. Discontinuation of the oral or topical antibiotic is warranted and replacing it with ampicillin (250 mg four times a day) or trimethoprim (600 mg/day) may improve the lesions. Treatment is challenging and recurrence is common. Isotretinoin is considered the treatment of choice, relapse following oral isotretinoin being much less likely [31].Malassezia folliculitis − also known as Pityrosporum folliculitis, this infrequently diagnosed condition is common young-to-middle-aged adults and affects the back, chest, and upper arms. The lesions are asymptomatic or slightly pruritic, monomorphic, dome-shaped, follicular papules with a central dell. Pustules, nodules, and cysts may occur in severe cases. The lack of comedones and occurrence of predominantly monomorphic lesions help differentiate this condition from acne on the back and chest. Malassezia folliculitis is commonly associated with tropical climates and immunosuppresion. Treatment with oral antifungals is the mainstay of treatment and topical such as 2% selenium sulfide, ketoconazole, and 50% propylene glycol in water have been found to be effective. Isotretinoin, due to its ability to reduce sebaceous secretions, has been found to be effective. Recurrences are common [32].Tinea barbae − this dermatophytosis of the bearded area is exclusively found on the face and neck in adult males. The animal species Trichophyton verrucosum and Trichophyton mentagrophytes var. mentagrophytes are responsible for the great majority of cases. The clinical picture commonly seen is that of the inflammatory variant wherein there is a pustular folliculitis. Exudation or crusting may be seen. The hairs are easily removable with forceps without eliciting any pain. The noninflammatory variant usually shows dry, circular, reddish, scaly lesions enclosing lusterless hair stumps. The hairs are either broken off close to the surface of the skin or plug the follicles helping in differentiating the condition from inflammatory acne. The treatment requires the use of systemic antifungals [33].Molluscum contagiosum − a common, mucocutaneous viral infection characterized by the occurrence of pearly, flesh to pink colored, dome-shaped, translucent papules with a distinct umbilication in the center of the lesion ([Figure 5]). The lesions predominantly affect children but may be seen at any age. They are common on the face, monomorphic in nature, and variable in size. A bacterial superinfection may be seen at times and one may see areas of eczematization surrounding the lesions (molluscum dermatitis). Use of a hand lens may help in identifying the umbilication associated with the lesions and clinching the diagnosis. Although spontaneous resolution is possible, treatment is usually sought for this condition and includes topical or invasive treatment options. Topical tretinoin, 5–10% potassium hydroxide, keratolytics, and imiquimod 5% cream are helpful in few cases. Curretage, needle extripation, cryotherapy, and electrocautery are common tools used to address these lesions [34].Other disorders mimicking inflammatory acne
Acne rosacea
This chronic condition is more commonly seen in the Caucasian population and is less frequently seen in the Asian subcontinent. The occurrence of acneiform papules and pustules in diffuse erythema make the condition difficult to differentiate from acne vulgaris ([Figure 6]a). A subtype of rosacea (Erythematotelangiectatic rosacea) may frequently present with telangiectasias, whereas granulomatous rosacea may present with firm, succulent, papular lesions on the face ([Figure 7]a,b) along with ophthalmic changes. Chronic ultraviolet exposure has been suggested to play a central role in the pathogenesis of this disorder as it leads to dermal connective tissue damage eventually resulting in vasodilation and vascular pooling resulting in the typical appearance of rosacea. There also seems to be a dysfunction of the epidermal barrier leading to sensitive skin in rosacea patients [35]. This distressing disorder may present with mild signs and symptoms such as transient flushing and dryness to severe manifestations such as persistent and recalcitrant erythema, edema, and phymatous formations. In India, the occurrence of a ‘rosaceiform eruption’ has become a common occurrence due to topical steroid abuse ([Figure 6]b) and rampant, unsupervised use of topical skin-lightening agents [36]. The lack of comedones, the occurrence of persistent erythema and/or flushing, telangiectasias, and rare ocular involvement help in differentiating this disorder from acne vulgaris. Commonly though there could be a delay in diagnosis and even an astute physician may falter as most cases present with papules and pustules similar to inflammatory acne. Treatment is challenging and long-term therapy is required. Topical treatments such as clindamycin, metronidazole, benzoyl peroxide, and azelic acid have shown promise. Recently 0.33% brimonidine gel, once daily received FDA approval for the treatment of rosacea-induced erythema. Low-dose antibiotics such as doxycycline and minocycline have been used for their anti-inflammatory activity. Oral isotretinoin has been successful as have surgical and laser therapies [36].
Figure 6 (a) Papulopustular rosacea and (b) rosaeciform eruption after prolonged topical steroid use.
Figure 7 (a) Granulomatous rosacea in a young male and (b) after treatment with isotretinoin for 3 months.Lupus miliaris disseminatus faciei
Lupus miliaris disseminatus faciei (LMDF) is a rare disease of acquired origin commonly affecting the face in adults of both sexes. LMDF is characterized by red-to-yellow brown papules on the face, particularly on and around the eyelids. Lesions may occur singly or in crops ([Figure 8]). LMDF which was earlier considered to be a tuberculid is now considered to be a distinct entity because of its characteristic histopathology and occasional involvement of noncentral facial areas [37]. Spontaneous resolution after crusting or pustulation within 1–3 years is standard. Residual scarring after individual papules regress may be disfiguring. The lack of comedones, pustules, nodules and cysts, lack of response to conventional anti-acne treatment, and granulomatous histology alerts the clinician to consider this diagnosis. Treatments with oral prednisolone, intramuscular triamcinolone, dapsone, tetracyclines, antimalarials, and isotretinoin have all shown variable success. More recently, tranilast has shown some benefit in the treatment of this condition [38],[39].
Seborrheic dermatitis
This is a chronic dermatitis which is characterized by erythematous, well-demarcated lesions with greasy scales. Seborrheic dermatitis has a variable presentation and the lesions may be in the form of papules, eczematous plaques, or pityriasiform to name a few. The dermatitis is common on hair bearing areas which are rich in sebaceous glands as well as the face and trunk. Particularly on the face and back seborrheic dermatitis may be confused with acne. On the face there is distinct involvement of the medial part of the eyebrows, the glabella, the perinasal area, and nasolabial folds. Areas of erythema and scaling occur, and may also involve the scalp (dandruff), upper eyelids (blepharitis), and the postauricular area where erythema, greasy scaling, and fissuring may be seen frequently. Involvement of the flexures (axillae) is not infrequent. Episodic variation in intensity is common. Since the lesions are eczematous and scaly, application of topical retinoids and use of keratolytics only aggravate the condition. Although recurrence is the rule, topical treatment with antifungals, corticosteroids, metronidazole, and topical calcineurin inhibitors have also shown promise. Further, shampoos containing selenium sulfide 2.5%, ketoconazole 2%, zinc pyrithione 1%, and ciclopirox 1.5% are useful in clearing the scalp. Systemic treatment with oral antibiotics is warranted for infected cases. Systemic corticosteroids and itraconazole are useful for severe cases as is low-dose isotretinoin [40].
Pseudofolliculitis barbae
Also called razor bumps, this condition is common in individuals with curly hair. It is common in African Americans and Hispanic males. Pseudofolliculitis barbae presents with painful, mildly itchy, inflammatory papules and pustules, in the beard area. The moustache area is usually spared. In severe cases, abscesses, firm papules with hyperpigmentation, hypertrophic scars, and keloids may also develop. Women with hirsutism who shave or use other methods such as tweezing, waxing, and depilatory use tend to develop pseudofolliculitis barbae. The condition is distinguished from acne due to the lack of any comedones and its distribution restricted to areas of shaving. Treatment is aimed at reducing the inflammatory component and decreasing the trauma induced by the hair removal process. Laser hair reduction is considered frequently as it helps decreasing the hair growth rate (hair becomes fine) with time thereby helping in decreasing the trauma induced to thick and coarse hair [41].
Hidradenitis suppurativa
Hidradenitis suppurativa (HS) is also known as ‘acne inversa’ and is a chronic, debilitating, inflammatory condition, which typically occurs during the second and third decade of life. Women are more affected than men. HS is particularly common in overweight or obese individuals. The disease is characterized by tender, indurated, papules, pustules, and subcutaneous nodules in the intertriginous areas. There may also be interspersed cysts, the coalescence of which leads to complications such as abscess formation, sinus tracts, fistulous tracts, and chronic infection mediated by migration of the pilosebaceous material. HS follows an unpredictable course, with frequent recurrences or an asymptomatic, quiescent state which may persist for months. A significant proportion of individuals may develop ‘tombstone comedones’ or permanently dilated pores within a burned out area of disease. Ultimately HS heals with scarring. The initial picture of HS may be confusing even to the best of clinicians although the full-blown picture of HS rarely causes difficulty in diagnosis. Treatment of HS is challenging, and there is no uniformly successful treatment modality. The detailed discussion of treatment of HS is beyond the scope of this chapter [42].
Acne keloidalis nuchae
Acne keloidalis nuchae is the result of a chronic folliculitis and has a distinct presentation. The disorder is characterized by follicular-based papules and pustules on the occipital scalp and posterior neck that form hypertrophic or keloid-like scars ([Figure 9]). It is commonly seen in young adult males. Chronicity is a rule of the disorder and follicular papules, eventually lead to the formation of keloid-like plaques in the hair bearing areas. Broken hairs, tufted hairs, and ingrown hairs can be seen along the margins of the keloidal plaque. These plaques become disfiguring and painful with time. Complications such as pus discharge and sinus tract formation are not uncommon in several variants of acne keloidalis nuchae. The disorder is usually easy to distinguish from acne vulgaris due to the distribution, morphology, and lack of comedones. Patient education is vital for treatment as most treatment modalities prove disappointing. Patients need to be told to avoid short haircuts, close shaving, tight-fitting collared shirts, and athletic head gear, which may lead to mechanical shearing of the hairs. Potent or superpotent topical steroids along with topical retinoids help in mild variants of the disease. A short dose of corticosteroids is helpful for inflammatory disease and intralesional triamcinolone acetonide for reducing firmess and pain due to the keloid. Oral isotretinoin for progressive disease is proven to be of use for progressive disease [42].
ConclusionWhile acne is a simple disorder to clinically diagnose, certain mimickers of the condition create a dilemma in diagnosis at times. The practicing clinician needs to make the patients aware about the various diagnostic possibilities and differentials, which may help in better diagnosis and management .
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