There are many illnesses and conditions in Medicine that are associated with skin disease.  Some of these conditions are quite rare. They include:  Sarcoidosis, Amyloidosis, the Histiocytoses,  Porphyrias. Endocrine conditions (Diabetes Mellitus, Hyper and Hypo-thyroidism ,adrenal disorders), Disorders of the joints, Disorders of the Gastro-intestinal tract, Generalised Pruritus,  Pruritus Ani.

It is impossible to write extensively about these conditions in a short presentation so I have picked the ones that we see in the clinics.

Sarcoidosis is a multi-system illness that can affect the skin but also the lungs, and many other organs. In the skin, it usually presents as a red/purple/brown plaque most commonly on the face, but it can appear anywhere on the body. The diagnosis is by skin biopsy (where a piece of the plaque is removed by your Dermatologist and sent to the pathologist to examine under a microscope). Your Doctor may also suggest a blood test. Erythema nodosum also presents in 1 in 4 patients with Sarcoidosis. These are painful red spots or nodules that present most commonly on the anterior shins. They fade away to leave a brown mark like a bruise. Lupus Pernio is another skin presentation of Sarcoidosis.  It is purple/blue discolouration of the nose, but can also occur on the ears and fingers. It is difficult to treat and can leave a scar.

The cause of sarcoidosis is unknown.  It is more common in women and affects the Irish, West-African and Puerto ricans. The treatment is multi-factorial and aimed at suppressing the disease. Many patients resolve completely in 2-5 years. 

Amyloidosis –  This is not common in Europe. It commonly affect patients from the Middle East, Asia, India and Central and South America. It is a chronic extremely itchy, condition that needs to be differentiated from Lichen simplex and Planus. It commonly affects the skins but also the upper legs and arms.  A biopsy is required for the diagnosis.  Another clue might be non-response or only slight response, to potent topical steroids.

Diabetes Mellitus ( DM).  Patients with DM have many skin complaints. They are are more prone to Candidiasis (thrush), and many bacterial, fungal, viral skin infections. Necrobiosis lipoidica is a waxy red/yellow plaque that presents on the shins of Diabetes.  Diabetic dermopathy presents as pigmented atrophic macules, usually on the lower limbs also. Fat hypertrophy from insulin injections can occur if the site of injection isn’t frequently rotated. Granuloma annulare which is a red non-scaley ring, with red papules around the margins of the ring, occurs particularly on the backs of the hands, ankles, knees and elbows. It is common in Diabetics.

Thyroid disorders can cause dry brittle sin and the hair can fall out. Adrenal disease can cause stretch marks and pigmentation.

Pruritus –  The is an extremely common presentation to the clinic.  The term generalised pruritus implies itching without and evidence of an itchy skin disease like scabies, eczema, urticaria or lichen planus. It is common with no obvious causes. It is treated with long-term anti-histamines and often resolves itself after a number of years. A careful history with a proper examination is necessary. Your Doctor will also suggest blood tests. Generalised itch or pruritus can also be caused by renal, liver and thyroid disease, Diabetes Mellitus, malignancy,  polycythaemia rubra vera, Senile pruritus (which is very common in the elderly and is treated with emollients) and nodular prurigo. Underlying medical conditions need to be ruled out before the Pruritus is treated.