Sunday, September 23, 2018

Atrophie blanche

A white area like this on the lower leg surrounded by light brown pigmentation and dot petechiae is called atrophie blanche. It is seen particularly in overweight diabetic patients with stasis dermatitis. The white area of skin is often firm due to underlying scarring and fat damage or panniculitis. Biopsies here are slow to heal but may show a segmental vasculitis. Treatment is difficult. The skin is already scarred and this will not change. However further damage can be reduced by dealing with the stasis through weight loss and support stockings and treatment of underlying varicose veins. Various vasodilator drugs have also been tried but the basic issues have to be remedied first to have any chance of success. Some cases of this condition occur after a definite vasculopathy with focal thrombosis in dermal vessels presenting with leg ulcers. This variant can be treated with aspirin, warfarin or low dose heparin.

Toxic epidermal becrolysis

This looks like a really bad burn but it is due to a drug! The condition is known as toxic epidermal necrolysis where a drug binds to the skin setting up a type 2 immune reaction where  the immune system attacks both the drug and the epidermal cell it is attached to. The result is full thickness epidermal necrosis where the epidermis just sloughs off from the underlying dermis. However equally severe reactions occur on mucosal surfaces with the lips, eyes, genital and perianal surfaces all eroding and crusting. The skin is very painful to touch and must be gently handled to prevent further skin sloughing. Patients are usually managed in a Burns unit where expert care can be given. Intravenous immunoglobulin and a drug called Rituximab which reduces antibody production give the best results but death can occur in around 30% of severe cases. This case was caused by 2 weeks of Sulfonamide for a bladder infection.

Shitake flagellate dermatitis

This is an unusual streaky rash seen on the back and abdomen. It arose following a meal of Shitake mushrooms. This is a distinctive rash described as a flagellate dermatitis. It follows the ingestion of raw or undercooked shitake mushrooms. These are popular mushrooms in Asian cooking but a rash may only occur in around 2% of people consuming them raw or undercooked. Sometimes the lesions do not blanch because lentinan, a thermolabile polysaccharide releases interleukin 1 which causes vasodilatation and haemorrhage. Linear petechiae can be seen elsewhere on the hands and feet. Localised swelling and fever can also occur. The rash will resolve spontaneously over a couple of weeks but some oral steroids early in the rash will help it resolve more quickly. It is the distinctive streaky nature of the rash that suggests the diagnosis. Bleomycin may cause a similar flagellate eruption but it resolves with hyperpigmentation.

Lichen simplex chronicus neck

This is the base of the neck posteriorly. It is a common site for stress induced scratching. When skin is rubbed or scratched repeatedly it thickens or lichenifies. Sometimes the skin markings just become more prominent but in other cases grouped papules and nodules are formed. This is more common in people of an Asian background with a history of atopic eczema. Unless the itch scratch cycle is broken this rash will persist indefinitely. You need to use a very strong topical steroid such as Diprosone OV cream or ointment to break that cycle by reducing the itch. Another option is to use diluted intra lesional Kenacort A10 with 1ml of solution to 3 mls of local anaesthetic. A small amount is injected intradermally at 1 cm intervals covering the area. This slowly diffuses over a 4 week period reducing the itch and the skin thickening. It helps to point out the cause and to instigate measures to help with the underlying stress.

Psoriasis flexural

We are used to psoriasis being a red scaly disease but when it involves the flexures the scale is much less apparent. The moist occluded surfaces mitigate against any scale formation but tend to encourage some secondary candida on the damaged moist surfaces. Sometimes these candida lesions present as satellite pustules with isolated pustules seen a few centimeters away from the main rash on a background of normal skin. Combination creams with 1% hydrocortisone and an antifungal preparation such as clotrimazole are ideal for treating both the psoriasis and the secondary candida. Stronger fluorinated topical steroid creams should not be used in these flexural occluded areas as absorption is enhanced and skin atrophy with striae formation can occur surprisingly quickly within weeks. Weight loss and having cotton between the breast surfaces to absorb sweat can help the condition resolve more quickly. Sometimes a tinea fungal infection can mimic this rash so taking skin scrapings of the edge for microscopy and fungal culture is always a good idea.

Median canaliform dystrophy

This condition is known as medial canaliform dystrophy of the nail. Note the horizontal grooves in the nail proximal to the split in an inverted fir tree pattern. Note also there is no damage to the cuticle and the posterior nail fold. A similar fir tree pattern can be seen in habit dystrophy of the nail usually the thumb, where the index finger nail is used to pick at the cuticle damaging the underlying nail matrix. This is known as a habit tic deformity. However median canaliform dystrophy has the central nail canal shown here. Some cases are familial. The thumbs are always involved. Cases have also occurred with oral isotretinoin therapy in cystic acne but heal after the drug is ceased. Other injury to the nail matrix can also cause it but most cases have no history of trauma. Treatment is clear nail polish to strengthen the nail and keeping it out of water which tends to soften keratin.

Hidradenitis suppurativa extensive

We are used to seeing hidradenitis suppurativa involving the axillae and groins but sometimes it becomes more extensive and sinuses and draining abscesses form extensively on the trunk as in this case. Hidradenitis suppurativa is considered a disease of apocrine glands usually affecting young people or obese diabetics. Bacterial cultures can sometimes be negative but always ask for anaerobic culture as well. Patients with this condition may have other inflammatory diseases  such as cystic acne and dissecting cellulitis of the scalp. Treatment with antibiotics and surgical drainage of abscesses was often unsuccessful and long term scarring and depression were commonly seen in these patients. A major recent development has been the availability on the PBS of the biologic adalimumab, a cytokine TNF alpha inhibitor given by subcutaneous injection every two weeks. This shuts off the inflammation in this disease and the abscesses and sinuses dry up. Therapy has to be continued in the longer term but patients get their life back!

Non surgical treatments for skin cancer

Non surgical treatment of skin cancer can have unfortunate consequences. This man has had cryotherapy for superficial basal cell carcinomas and SCC in situ on his back on multiple occasions. If cryotherapy is not carried out properly with adequate edge margins then you get recurrences like this. Elderly patients living alone find it impossible to apply creams to the back such as Imiquimod or Efudix.  Photodynamic therapy with amino laevulinic acid can be effective for small lesions on the back but would not clear recurrences like this. Any excisional surgery here would be very extensive but could be done over a series of treatment sessions. Radiotherapy could be carried out to the whole area but would require 25 to 30  fractionated treatments. Another technique that could be tried on the back is curette and cautery but any deeper areas of recurrence might be missed and the wounds would require clinic visits for dressings until crusted over. These lesions were biopsied and were scc in situ. I will discuss radiotherapy and staged surgical excision with him.

Flexural drug eruption

A flexural rash like this in an elderly incontinent patient might have you thinking of irritant dermatitis or psoriasis or perhaps a candida infection but the curious thing was it only occurred when she was admitted to hospital from her nursing home with a chest infection. She would be fine when she arrived but a couple of days later this rash would appear in the groin and less so in the axillae, accompanied by a few annular lesions on her trunk. It took a couple of admissions to work out that this was a flexural fixed drug reaction to amoxicillin antibiotic she would be given for her chest infection. This condition has also been described as Symmetrical Drug -related Intertriginous and Flexural Exanthema SDRIFE . Various other drugs have been reported as causing this distinctive flexural rash but Ampicillin is the commonest. It is similar to systemic contact dermatitis where an individual is initially sensitised to a contact allergen and is subsequently exposed to it through a systemic route and develops a symmetrical localised dermatitis, often on the buttocks and groin flexures. The classic cause was mercury exposure from a broken thermometer where subsequent inhalation of mercury vapour caused a rash that was colloquially known as the Baboon syndrome because of the red bottom!

Sunday, July 16, 2017

Sweet's Syndrome and Pathergy

These two lesions are different stages in the same condition. Sweet's syndrome is a curious hypersensitivity syndrome with a massive infiltrate of neutrophils into the dermis giving a pseudoblistering like lesion. The purple, exophytic lesion on the finger looks like Orf, a pox virus infection from sheep or a pyogenic granuloma or even a malignant tumour but it started as a pustule similar to that seen in image one. These pustules can arise at sites of injury such as needle stick injuries from taking blood where the phenomenon is known as pathergy. Patients showing Sweet's syndrome will have a significant leukocytosis in a blood count and sometimes fever and joint swelling. 20% of cases may be associated with a blood or solid organ tumour malignancy and also with inflammatory bowel diseases Crohns and Ulcerative colitis or even rheumatoid arthritis. In many recurrent cases though the cause is not known. Cases respond to oral steroids tapered over 3 weeks. Lesions will heal without scarring which is surprising looking at that finger!