Dermatology

This is a prototypical case of acute contact dermatitis to benzoyl peroxide that the patient had been applying for her mild to moderate papulo-pustular acne. Twice-daily application of hydrocortisone 2.5% cream led to prompt resolution of the rash.

Biopsy of the flat area of this erythematous patch revealed superficial basal cell carcinoma while biopsy of the more nodular component revealed deeply infiltrating basal cell carcinoma.

This non-tender, freely mobile, rubbery-feeling nodule is a classic lipoma. Diagnostic contenders include epidermal cyst and cutaneous metastases.

Eccentric and irregular pigmentation prompted a biopsy in this elderly woman with a history of basal cell carcinoma and melanoma. The surprising diagnosis was a heavily pigmented squamous cell carcinoma in situ.

The puncta, with a black center, clearly identified these as classic epidermal cysts.

Biopsies of this large variegated pigmented plaque ruled out lentigo maligna melanoma and gigantic seborrheic keratosis.

This translucent dark pink nodule located just behind the nail is the classic presentation of a digital myxoid cyst.

After a dog bite, trauma in the form of a subungual hematoma and shallow lacerations prompted a 10-day course of amoxicillin-clavulanate. This antibiotic is also useful for cat and human bites that appear to be at high risk of becoming infected.

A biopsy revealed non-caseating granulomata, and culture revealed Mycobacterium marinum. This patient had a fish tank at home, and used his right hand to perform maintenance.

This pigmented macule clearly stands out against a bland background of fair-complected skin. This is known as the “ugly duckling” sign. Such lesions should always be viewed with suspicion and a biopsy is generally indicated.

This tumor is a low-grade soft tissue sarcoma. Metastases are uncommon, but local recurrence is very frequent. Mohs surgery is the optimal treatment modality.

The shallow ulceration surrounded by a ring of erythema is characteristic for aphthous ulcers (canker sores). This patient’s otherwise negative history rules out Behcet’s disease.

The persistent pigmentation on this woman’s hands corresponds to areas of intralesional injections of bleomycin for recalcitrant warts.

Adult-onset psoriasis is uncommon without a precipitating factor. In this patient’s case, an oral beta-blocker precipitated the psoriasis.

Contact dermatitis to paste-on fingernail decorations developed when the patient held her lower eyelid down with her index finger to insert her contact lenses.

Melanoma in pre-adolescent children is extremely rare, but not totally unknown. Because this lesion had recently become larger and darker, the lesion was excised; histology confirmed a benign nevus.

This nodule on the neck is a typical location and appearance for an epidermal cyst. If the cyst has never been inflamed or infected, it may be removable through a very small punch biopsy followed by lateral pressure or a small linear incision.

In the current milieu, the clinician should assume that MRSA is responsible for furuncles, until culture proves otherwise. Incision and drainage is the most important part of therapy, but oral antibiotics should be considered in large lesions, very young or very old patients, and when cellulitis surrounds the boil.

Given this patient's history, this wart might have been over-treated as a presumed squamous cell carcinoma had not a biopsy been obtained.

Some skin neoplasms are quite subtle and do not present as obvious exophytic lesions. This basal cell carcinoma presented as a subtle area of asymptomatic discoloration under the patient’s eye.

This is a classic case of herpes zoster. Note that the rash is limited to T5-6 dermatomes.

This biker asked that his wound be rinsed with hydrogen peroxide, which is now felt to be irritating to tissue and no longer recommended for use in rinsing out a traumatic wound. Water or saline is preferable. Also, superficial abrasions heal better when kept moist.

It is rare for acne of this severity to develop in normal, healthy adults. This picture strongly suggests patient manipulation of more minor lesions. When the clinical picture is unusual or improbable, always consider the possibility of factitious disease.

CT scan verified thyroid gland localization of this asymptomatic neck mass that proved to be papillary thyroid carcinoma on needle aspiration biopsy. Thyroidectomy confirmed the diagnosis of cancer.

This is a classic keratoderma, which can be due to a variety of congenital defects in keratinization or acquired in association with disease states. Retinoids, systemic and topical, are the treatments of choice.

This solitary, very pruritic, annular lesion suggests dermatophytosis. KOH preparation verified the presence of Tinea faciei. This infection is usually associated with contact with a new kitten or puppy.

This clustered grouping of small, shallow erosions surmounting a slightly indurated plaque is characteristic for “cold sores.” Because no vesicles were present and the lesions appeared to be crusting over, the patient was advised to apply an OTC cream (docosanol 10%) per package insert instructions.

These small, pruritic papules appeared in the morning, which strongly suggests the bite of a nocturnal feeding arthropod. Insect bites arranged in clusters of 3 is typical for, but not diagnostic of, bedbug infestation.

This green discoloration is the result of subungual Pseudomonas aeruginosa colonization. Pathogenic bacteria can enter this space via many causes, including trauma or underlying lesions.

Guttate psoriasis often appears in conjunction with an upper respiratory infection, particularly streptococcal tonsillitis, as it did in this patient. This phenomenon is more common in children.