The extremely pruritic, rather polymorphic chronic skin rash in DH is more easily recognized by the typical distribution of the rash than by the morphology of the skin symptoms. The skin symptoms are, in order of frequency, above the elbows, knees, buttocks, and shoulders (Figs. 44.2, 44.3, and 44.4), but the exanthemas might extend to the extensor surfaces of the lower arms and lower legs and to the midline of the back. The grouped, 1- to 3-mm large erythematous papules, seropapules, vesicles, small blisters, crusted erosions, and excoriations heal with hypo- or hyperpigmentation resulting in the majority of cases in a polymorphic rash. Rarely confluent, stable urticarial plaques develop in the axillary region or mostly in childhood also on all the typical distribution sites of the body. In some patients, due to the severe itch and aggressive excoriation, lichenification might predominate the skin signs on the typical location (Figs. 44.2, 44.3, and 44.4). Unique feature of DH is the presence of 1–2 mm large brownish acral purpuras on the fingers, toes, and palmoplantar surfaces (Fig. 44.5). These are not always present but may be the solely rather hidden symptoms of the disease. DH rarely might show grouped “herpetiform” vesicles or even large bullae [1, 4, 5].

DH can start at any age; it is not rare in small children, but may also develop first at very old ages. In milder clinical forms spontaneous symptom-free periods interrupt the active disease for days, weeks, or months, while other patients continuously have very severe skin disease for years. Pruritus is always severe and is characteristically preceding the recurrence of cutaneous signs and might challenge the otherwise symptom-free time of the patient. Severe DH is continuously pruritic, but the extension of skin lesions and the severity of itch are changing. Some DH patients enjoy symptom-free summers due to the beneficial effect of sunshine; few, however, suffer more due to the increased sweating. Peroral or local iodine challenge might induce extended cutaneous side effects [1, 4, 5].

DH patients under a strict GFD are free of skin symptoms and even have a longer life expectation than the general population in Finland [6]. However, some DH patients without a GFD will also be temporarily or permanently symptom-free and spontaneously go into a cutaneous remission. A spontaneous remission of DH is considered when the patient has no skin rash for at least 6 months without any medication and without gluten-free diet (GFD). These remissions are rare but may develop in 10–25 % of untreated DH patients [7, 8]. However, the prognosis of DH is always determined by the outcome of associated diseases, e.g., celiac disease, malabsorption, autoimmune diseases, and underlying tumors, and these are mostly determined by the diet-dependent GSE.

In DH patients without a strict GFD, the underlying celiac disease persists and leads to further secondary malabsorption-associated diseases and tumors (see later), even in rare cases of long lasting skin remissions [7–9]. Symptoms of malabsorption are rather common consequences of latent or silent GSE in DH including microcytic or macrocytic anemia associated with iron, folate, or B₁₂ deficiency, hair loss due to zinc and iron deficiency, as well as early and/or severe osteoporosis. Weight loss but weight gain with an unfavorable body mass index (BMI) can be also present [10]. Symptoms of GSE in DH rarely include severe diarrhea, more commonly constipation, bloating, abdominal discomfort or pain, associated sometimes with consequences of secondary lactose intolerance [1, 4, 5, 8, 11].

Children with DH may have delayed development and puberty, short stature, and a high BMI.

DH patients rather commonly have incomplete dental mineralization on permanent and decidual teeth indicated by the so-called celiac-type enamel defects, severe caries, or early tooth loss, but the symptoms are usually milder than those in severe GSE [1, 5, 7, 8]. A chronic, atrophic corpus gastritis with metaplasia can be present in 16 % of DH patients and is associated with a higher incidence of Helicobacter pylori infection [11].

DH patients, similar to celiac patients, should be screened for autoimmune thyroiditis and type 1 diabetes (anti-islet AB). Vitiligo, pernicious anemia, and alopecia areata are also rather common. Symptoms of lupus erythematosus, Sjögren syndrome, and primary biliary cirrhosis and IgA nephropathy are rare but should be recognized in DH [5, 12, 13].

Gluten sensitivity is the most common cause of the sporadic idiopathic cerebellar ataxia (gluten ataxia) [14, 15]. Further central nervous system findings described in GSE are epilepsy, myoclonus, dementia, and multifocal leukoencephalopathy. Peripheral nervous system involvement includes axonal and demyelinating neuropathy. Myopathies, dermatomyositis, and fibromyalgia have also been described [16].

The lymphomas in DH and GSE include enteropathy-associated T-cell lymphoma or other lymphomas, with only 1 % comprising non-Hodgkin lymphomas [9]. These patients usually have a very poor prognosis. The relative risk in untreated celiac disease and DH is enhanced. They arise from phenotypically abnormal intraepithelial lymphocytes, with loss of the CD8 and, rarely, CD3 expression. There is a risk reduction documented under strict GFD. Other tumors include B-cell lymphomas, cutaneous lymphomas, and adenocarcinoma of the small bowel.

Iodine sensitivity is a typical feature of DH. Selective immunoglobulin (Ig) A deficiency is more common in celiac patients and has been described also in DH [1].

The major treatment for DH is a strict GFD to prevent the development of lymphomas and other diseases associated with GSE [1, 5, 17]. This is suggested, even if the skin symptoms spontaneously disappear, because the GSE persists. The skin manifestations rarely disappear under a GFD within a few weeks, commonly lasting for months or for a few years.

In the early phase, associated lactose intolerance might accompany the GSE due to intestinal damage. For these patients, for a few months at least, a diet free of lactose and gluten is suggested. The consultation with the gastroenterologist is always advisable.

For diabetic patients, the double diet—low carbohydrate and gluten-free—might be very difficult, but both diets seem to be clinically effective only when properly applied.