A 15-year-old boy with Down syndrome (DS) presented with a 12-month history of multiple, asymptomatic papules on the extensor aspect of the limbs and buttocks. The mother and patient denied any scratching. A 1-month trial of Tetracycline 250 mg BD had no effect, and a combination of betamethasone valerate and fusidic acid (Fucibet Ò , Leo Pharm, Princes Risborough, Buckinghamshire, UK) was unhelpful. No relevant family history was known. Examination revealed multiple 5 to 10 mm erythematous papules and nodules with central keratin plugs on the upper and lower limbs and buttocks, some occurring in a linear fashion (Figs. 1 and 2). Folliculitis was evident on the buttocks and to a minor degree on the thighs. Laboratory investigations were all normal or negative including full blood count, renal and liver function, bone profile, glucose, inflammatory markers, thyroid function, antinuclear antibody (ANA), complement, and immunoglobulins. Skin swabs revealed no growth. Skin biopsies from the arm and thigh showed similar features (Figs. 3 and 4).A 5-year-old boy presented with approximately 15 skin-colored to bluish, translucent papules of 1-3 mm diameter scattered over the dorsum of his nose (Fig. 1). The parents had first noticed them 2 years previously and reported a marked increase in number and size after physical exercise as well as seasonal variation, with exacerbation during summer months (Fig. 2). The boy was said to sweat easily, especially in the craniofacial area. He was small, with height and weight just above the 3rd percentile, but was otherwise in good health and on no medication. Laboratory parameters including thyroid hormones and autoantibodies revealed no pathological findings. A facial Minor's iodine-starch test showed pronounced sweating on the forehead, cheeks, and chin, after physical exercise, while the nose was largely spared. Correspondingly, gravimetric assessment of sweat production showed it to be remarkably high on the forehead while being within normal range on the palms. After informed consent from the parents, one of the papules was removed by punch biopsy and histologically examined (Figs. 3 and 4).A 2-year-old boy presented to the Emergency Room with a 4-day history of a rash and a 1-day history of fever. The eruption began on his back and rapidly spread to become generalized over 24 hours. He was sleeping poorly due to severe pruritus, and his appetite was diminished. No response occurred to treatment with oral antihistamines or prednisolone. His previous medical history included asthma, controlled with intermittent use of a salbutamol inhaler, and dermatitis from contact with sleeper snaps in infancy. His mother had recently taken an oral antibiotic for presumed streptococcal pharyngitis.On examination, his temperature was 38.3°C. He was irritable and scratching. His skin was erythrodermic with coalescing 2 to 5 mm edematous red papules involving the trunk, extremities, face, and ears (Fig. 1). The perioral skin, palms, and soles were spared. The oral mucous membranes and conjunct...