Dr. Cohen serves as Section Editor for Pediatric Dermatology: What's your Dx? and is director, Pediatric Dermatology and Cutaneous Laser Center, and associate professor of pediatrics and dermatology at Johns Hopkins University School of Medicine, Baltimor

Bernard A. Cohen, MD

Tinea incognito is a dermatophyte infection that has been altered by use of topical or systemic corticosteroids. It lacks the classic features of a ringworm infection due to corticosteroid suppression of inflammation and altered local immune response. Tinea incognito often takes on atypical or even bizarre morphologies.

Dermatophyte infections of non-hair-bearing skin are typically well demarcated annular patches, or plaques with central clearing. The appearance may vary by location, and may start as a simple papule. The characteristic lesion subsequently develops with an expanding elevated, red scaly border. Vesicles, pustules, and/or crusts may be present within the border when inflammation is intense.

A number of clinical patterns have been described with tinea capitis:

Symptoms of tinea capitis depend on the clinical pattern, and can vary from minimal pruritis and no alopecia to diffuse tenderness with purulence and scarring alopecia.

However, treatment with topical or systemic steroids may suppress local immunity and inflammation, resulting in unusual clinical presentations and a delay in diagnosis. Tinea capitis and tinea corporis must be considered in this setting, even when the clinical pattern is not typical.  

The differential diagnosis for tinea incognito includes seborrheic dermatitis, atopic dermatitis, alopecia areata, telogen effluvium, bacterial folliculitis, and psoriasis.

  The presence of tinea at other body sites and in other family members should increase the index of suspicion for tinea. A potassium hydroxide preparation is usually positive and allows for immediate confirmation of dermatophyte infection. However, a fungal culture is still the gold standard for diagnosis, and should be sent especially when a patient's infection involves the scalp. 

Effective treatment of tinea incognito requires discontinuation of steroids. This may result in an increase in inflammation, as well as symptoms that can be managed with a slower taper to lower potency and less frequent applications of the topical steroid. Warning parents of this rebound phenomenon should minimize the risk of prolonged additional use of steroids.

Articles

Tinea incognito is a dermatophyte infection that has been altered by use of topical or systemic corticosteroids. It lacks the classic features of a ringworm infection due to corticosteroid suppression of inflammation and altered local immune response.

Balancing the scales

The boy's mother reports that the rash appeared two days after he played in a park for several hours. 

The rest of your examination is unremarkable.  

Poison ivy dermatitis is a major source of contact allergy in children, particularly during the summer. The causative plant and its relatives (including the commonly named poison oak and poison sumac) are classified under the botanical genus 

 but are sometimes included in the genus 

Poison ivy, the likely culprit in this case, is a three-leaved tall shrub or woody, rope-like vine that grows within grasses, on trees and fences, and in vacant areas. It flourishes in most regions of the continental United States, and is very common in some areas. 

The dermatitis results from a delayed contact hypersensitivity type-IV reaction to the oleoresin (urushiol), of which the active sensitizing ingredient is pentadecylcatechol.  

Characteristic lesions appear in susceptible children within one to three days after exposure, although they may develop as early as within 8 hours after exposure in a highly sensitized person. Seventy percent of people in the United States demonstrate a genetic susceptibility to 

 dermatitis when they are exposed to the sensitizing oleoresin in plants' leaves, stems, and roots.

The eruption of poison ivy is characterized by pruritic red papules, vesicles, and bullae

  that are usually linear or angulated, either because of the manner of exposure to the plant in woods or the backyard or because scratching transfers the urushiol to adjacent areas (Koebner reaction). Black lacquer-like deposits that often appear within lesions when sap from any 

species comes in contact with dry skin, and that are evident in this patient, are a reliable marker for this allergen.

  The nature of the silver-white crust on this patient's lesions is uncertain. 

Linear lesions of poison ivy dermatitis can usually be distinguished from other dermatitic disorders, such as 

, which tend to be symmetric in distribution

 and that present in characteristic age-related patterns.

 triggered by such allergens as sun block and fragrances. 

When vesicles and bullae are prominent, poison ivy dermatitis must be distinguished from 

Exposed persons should wash thoroughly as soon as possible (within minutes of contact is best) to remove the oil from skin.  Fresh allergen can be transmitted to other areas of the body by surface-to-surface contact and, within minutes, becomes fixed to skin, where the allergic reaction ensues. 

Contaminated clothing and shoes should be washed with soap and water within a few minutes after exposure to  remove the urushiol before it dries to prevent it from becoming antigenic indefinitely.

A potent topical corticosteroid may help reduce the intensity of the reaction but does little to hasten involution of lesions.

				  A systemic antihistamine or antipruritic may help ease the itching. 

A 9-year-old boy has developed an itchy vesicular rash on his left leg that has spread to his other leg and to both arms and hands. What is the diagnosis?

Linear rash leaves your patient itching

				 You are asked to see a 6-year-old boy who has a history of a skin eruption, intermittent fever, and generalized weakness. His mother is concerned about increasing puffiness around his eyes and red bumps on the bony prominences of his hands, elbows, and knees (see the photograph).  			

The history and clinical findings are typical of juvenile dermatomyositis (JDM). Further evaluation-including elevated serum levels of creatine kinase and aldolase, skin biopsy findings consistent with connective tissue disease, and evidence of muscle inflammation on a magnetic resonance imaging (MRI) scan-all confirm your clinical suspicion. 

JDM is a chronic inflammatory disorder of unknown etiology that primarily affects muscle and skin. The diagnosis requires not only the presence of one of the characteristic skin findings, but also at least three of four of the following features: 

The skin manifestations of JDM include the characteristic heliotrope rash of violaceous erythema and edema of the malar and periorbital skin. A scaly, red, psoriasiform eruption may involve the extensor surfaces of knees and elbows. When this eruption appears on the distal interphalangeal joints, the papules and plaques are referred to as Gottron papules.

  Seborrheic-like dermatitis of the scalp is often present in JDM. Nail findings include periungual erythema and nailfold telangiectasias. 

Over time, children with JDM may develop chronic skin changes, including atrophy, hyperpigmentation, fibrosis, and telangiectasias.  Late in the course, deposition of calcium in skin, muscle, and joints may result in debilitating contractures, painful ulceration, and cellulitis.

The facial rash of JDM in children can suggest 

; in fact, some of the clinical features of these two connective-tissue diseases overlap. Severe muscle involvement, with evidence of myositis on MRI or muscle biopsy, or both, and elevation of muscle enzymes, is characteristic of JDM and distinguishes the two disorders. 

In early JDM, when muscle symptoms are subtle, the psoriasiform eruption on the extensor surfaces of the extremities can be confused with 

The diffuse erythema and scaling of the scalp in JDM can mimic 

 or psoriasis before the other signs and symptoms of JDM appear. 

An oral corticosteroid, 1-2 mg/kg/day, is the initial treatment of choice for most patients with JDM. Although most patients respond to steroid therapy, some children suffer severe complications of the disease, including gastrointestinal tract and skin ulcerations and dystrophic calcification.

  Other immunosuppressive agents, including methotrexate, azathioprine, intravenous immunoglobulin, and cyclosporine, have been used to treat patients who fail to respond to, or experience severe side effects from, a corticosteroid. 

Physical therapy is important to promote recovery. Patients should be encouraged to minimize the risk of a photosensitivity reaction by wearing sunscreen and avoiding exposure to intense sunlight. Muscle strength and enzyme levels should be monitored continuously for signs of relapse. 

The prognosis for children who have JDM has improved with the advent of the use of corticosteroids. Early, aggressive treatment has been demonstrated to improve outcome and decrease the incidence of calcinosis.

1. Bohan A, Peter JB: Polymyositis and dermatomyositis (first of two parts). 

2. Sontheimer RD: Dermatomyositis: An overview of recent progress with emphasis on dermatologic aspects. 

3. Santmyire-Rosenberger B, Dugan EM: Skin involvement in dermatomyositis. 

4. Huber AM, Lang B, LeBlanc CM, et al: Medium- and long-term functional outcomes in a multicenter cohort of children with juvenile dermatomyositis. 

5. Fisler RE, LIang MG, Fuhlbrigge RC, et al: Aggressive treatment of juvenile dermatomyositis results in improved outcome and decreased incidence of calcinosis. 

A boy with a history of skin eruption, intermittent fever, and generalized weakness now has red bumps on the bony prominences of his hands, elbows, and knees. What's the diagnosis?

Weeks of weakness, then reddish bumps on prominences

PEDIATRIC DERMATOLOGY: 
  What's your Dx? 

Sole manifestation: Nodule in a newborn boy

 An ulcerated nodule was noted on the sole of this healthy 2-week-old boy at   birth (Figure 1). The nodule did not seem tender and, since birth, had flattened   slightly. The mother's pregnancy, labor, and delivery were uncomplicated. The   boy had gained nearly a pound since being discharged from the nursery. 

Diagnosis: Self-healing reticulohistiocytosis 

 Skin biopsy revealed an ulcerated nodule comprising primarily histiocytes   and lymphocytes and extending into the deep dermis. Testing for immunohistochemical   markers was positive for protein S100 and CD1a antigen, expressed as Langerhans   cell histiocytes.

 A complete physical examination failed to reveal evidence of visceral involvement: Specifically, the infant had neither hepatosplenomegaly nor lymphadenopathy. Chest radiographs and a skeletal survey were negative. A complete blood count and liver function tests were normal.

 Self-healing reticulohistiocytosis is a generally benign, self-limited variant of Langerhans cell histiocytosis. Characteristics of self-healing reticulohistiocytosis are: 

 the presence of a regressing solitary, ulcerated nodule 

 typical histologic findings with histochemical markers 

 This disorder was initially described by Hashimoto and Pritzker in 1973 in   a child who had many congenital cutaneous nodules, all of which resolved within   the first few weeks of life.

Biopsy showed histologic markers of   Langerhans cell histiocytes, including typical Bierback granules (Figure 2)   in 10% of infiltrating cells.

The nodules appear as solitary or only a few lesions. Many reddish-purple nodules, however, can appear on patients with the congenital form of self-healing reticulohistiocytosis. The diameter of the nodules ranges from 0.5 to 2 cm, and the nodules regress over a few days or months. Often, the nodules develop central necrosis with a peripheral rolled edge.

 Affected infants do not usually develop systemic disease, but there is considerable overlap among self-healing reticulohistiocytosis and other benign cutaneous and systemic histiocytic disorders.

Consequently, the pediatrician must be careful when counseling parents about prognosis.

A small percentage of patients do develop systemic disease, or limited visceral involvement, months or years later. This happens even when there is no evidence of hepatosplenomegaly or lymphadenopathy, and when imaging studies (including a chest radiograph and a skeletal survey) are negative and laboratory tests (liver function tests and a CBC) are normal. Regular monitoring of growth and development during childhood and observing the patient for signs of systemic disease are required.

 A solitary ulcerated nodule in a newborn presents a broad differential diagnosis that includes congenital leukemia, lymphoma, and a number of rare metastatic solid tumors, including neuroblastoma, adrenal carcinoma, and renal carcinoma. A solitary mastocytoma may present as an isolated ulcerated nodule. You will also need to exclude primary vesiculobullous eruptions such as varicella, bullous impetigo, and herpes simplex virus infection.

 The nodule in this patient resolved with minimal atrophy   by 4 months of age. At 6 months, he is thriving without evidence of systemic   disease. 

 1. Hashimoto K, Takahashi S, Lee RG, et al: Congenital self-healing   reticulohistiocytosis: Report of the seventh case with histochemical and ultrastructural   studies. 

 2. Hashimoto K, Pritzker MS: Electron microscopic study of   reticulohistiocytoma: An unusual case of congenital self-healing reticulohistiocytosis.   

 3. Jang KA, Ahn SJ, Choi JH, et al: Histiocytotic disorders   with spontaneous regression in infancy. 

The next installment of Pediatric Dermatology: What's         your Dx? will appear in January 2003      

 For this case and related images, or to contribute new         images from your own cases, see Dr. Cohen's Web site at 

DR. COHEN, who serves as section editor for Pediatric Dermatology: What's   your Dx?, is director, Pediatric Dermatology and Cutaneous Laser Center, and   associate professor of pediatrics and dermatology at Johns Hopkins University   School of Medicine, Baltimore. He is a contributing editor for 

 

Bernard Cohen. Pediatric dermatology: What's your Dx? 