Four presentations of skin conditions

The presentation, diagnosis and management of cutaneous infection with Mycobacterium chelonae, basal cell carcinoma, leiomyosarcoma and disseminated superficial actinic porokeratosis.

Figure 1: cutaneous infection with Mycobacterium chelonae
Figure 1: cutaneous infection with Mycobacterium chelonae

Skin infection with mycobacterium chelonae

This 68-year-old patient presented to dermatology with a gradually evolving confluent eruption of multiple nodules on his left upper arm. Some of these had begun to ulcerate and discharge purulent material. The lesions were tender but cool to the touch. He was systemically well. His GP had prescribed several courses of antibiotics, with no benefit. Swabs for bacterial culture were negative.

The patient had a number of comorbidities, most importantly, longstanding rheumatoid arthritis, for which he took oral prednisolone 8mg daily. He had been treated with etanercept and rituximab, but had not taken a biological agent for 12 months.


Cutaneous infection with Mycobacterium chelonae

Clinical features and management

The clinical picture and history of treatment with biologics and prednisolone was highly suggestive of a deep-seated mycobacterium infection. Abscess formation in the dermis and subcutis is characteristic. Such infections should always be considered when abscesses are cold.

Histology demonstrated granulomatous inflammation and a Ziehl–Neelsen stain demonstrated numerous acid-fast bacilli. Subsequent culture isolated Mycobacterium chelonae and the patient was referred to a respiratory physician for consideration of antituberculous therapy.

With an increasing number of patients now taking immunosuppressants and biologics, we must be aware of the risk of mycobacterium infections. Mycobacterium chelonae occurs commonly in soil and water, and skin infections are often caused by direct inoculation. This organism can be particularly resistant to standard antituberculous regimens.

Figure 2: Sebaceous naevus and basal cell carcinoma

Sebaceous naevus and basal cell carcinoma

This 43-year-old woman was born with a lesion on her left anterior scalp line. The lesion had been flat, but became more rugose and warty throughout her childhood and early adolescence. It then remained static until 18 months ago, when an area of nodularity developed, which began to superficially ulcerate at the lower pole.


Basal cell carcinoma in a congenital sebaceous naevus

Clinical features, differential diagnosis and management

Differential diagnoses include aplasia cutis, juvenile xanthogranuloma, solitary mastocytoma and verrucous epidermal naevus. Sebaceous naevi are hamartomas composed of sebaceous glands. They occur most commonly on the scalp, neck and face. Verrucous epidermal naevi are more common on the trunk and limbs. Occurrence is generally sporadic. Incidence is 0.3% in neonates and is equal among the sexes.

A range of appendageal tumours can develop within such naevi, usually trichoblastomas. These are often benign, but there is a possibility of malignant change. The naevi themselves present as solitary raised plaques that can be pink, yellow or orange and range in diameter from 1-10cm. If they are on the scalp, they are devoid of hair. They usually become more prominent in adolescence.

Rapid enlargement or ulceration should raise the possibility of malignant change. However, the risk is low, so the historical practice of excising all such lesions is difficult to justify. A more conservative approach, with counselling, is generally appropriate.

Figure 3: Leiomyosarcoma


This 77-year-old patient developed a tumour on his forearm that grew rapidly over three months. There was a wide differential diagnosis, including malignant melanoma, Merkel cell tumour or angiosarcoma. The patient had an urgent excision and histology confirmed leiomyosarcoma.



Clinical features and management

Leiomyosarcoma is a rare tumour of smooth muscle which usually occurs in patients over 60 years old, although it has been described in childhood. Diagnosis is histological. The clinical approach is governed by the EFG principle – any lesion that is elevated, fixed or firm and growing should be considered for excision and histology.

The tumour may be in the dermis, the subcutis or below. The most common site is the thigh, followed by the head, neck, arm and trunk. Metastatic spread can be both haematogenous and lymphatic. Wide local excision is the treatment of choice.

Figure 4: Disseminated superficial actinic porokeratosis

Disseminated superficial actinic porokeratosis

This 76-year-old woman with Fitzpatrick skin type I had developed multiple well-circumscribed, asymptomatic, marginated, annular lesions over a number of years. They were predominantly on her lower limbs, with a few similar lesions on her forearms.


Disseminated superficial actinic porokeratosis

Clinical features, differential diagnosis and management

This condition presents most commonly on sun-exposed surfaces in white females. It demonstrates an autosomal dominant inheritance pattern and can manifest from the age of 40 years onwards. The role of UV light is unclear and the risk of malignant progression is minimal.

Differential diagnoses include actinic keratoses and porokeratosis of Mirbelli.

The lesions range from 3-10mm in size and are usually asymptomatic, but can be mildly itchy. They can be numerous and appear more prominently in the summer months. Clinical diagnosis is determined by the sharp margination with a slight raised edge, differentiating them from simple solar keratoses. Histopathology will show a characteristic cornoid lamella.

Treatment is not usually required. Judicious cryotherapy to individual lesions can be considered and 5-fluorouracil cream, topical and oral retinoids have been tried, but these treatments are not reliable, effective or often clinically indicated.

  • Dr Brian Malcolm is an associate specialist and GPSI in dermatology in Barnstaple, Devon, honorary associate lecturer, Cardiff University, and committee member of the Primary Care Dermatology Society

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