Question:

A 68-year old woman, admitted to hospital for management of acute cerebral stroke, was unconscious and remained bedridden for the past 18 hours. She was found to have tiny blistering skin rash at the chest and back as shown. The rash was characterized by small clear and very superficial vesicles and no inflammatory reaction was noted. No scratch marks and no abnormality were noted in the mucous membranes.

Answer: D. Miliaria crystallina

The diagnosis is miliaria crystallina. This patient had quite profuse sweating after admission. The lesions are characterized by small, clear and very superficial vesicles with no inflammatory reaction. These fragile vesicles develop as eccrine sweat ducts become obstructed in its very superficial portion. Predisposing factors include high fever and occlusion and the clinical appearance is usually diagnostic. Bedridden patients in whom fever produces increased perspiration can have this condition but they are often self-limiting, transient and last only for few days so that they may not be noticed by the patients. It can also be found in newborn. It is hypothesized that the occlusion at different levels of the sweat duct leads to different types of miliaria. The occlusion in the sweat duct prevents normal secretion from eccrine sweat gland and the escape of sweat into the adjacent tissue result in miliaria. When the very superficial part of eccrine duct is obstructed, miliaria crystallina will occur. The characteristic appearance of tiny water droplets being sprayed onto the skin surface is easy to recognize. The vesicles tend to rupture at the slightest trauma and no inflammation was accompanied. Miliaria rubra or prickly heat usually presents as discrete pruritic erythematous papulovesicles. Usually the flexural regions, e.g. inframammary folds, inguinal regions and axilla, will be involved. The site of eccrine duct blockage and injury is a bit deeper than that of miliaria crystallina. The level of blockage is in the prickle layer with mild spongiosis and inflammation.

Transient acantholytic dermatosis or Grover's disease often presents with pruritic, discrete pink papules or papulovesicles. It affects middle-aged or elderly men more often and the rash is transient, lasting from weeks to months. Histopathology shows typical focal acantholytic dyskeratosis and needs to differentiate from Darier's disease, pemphigus and Hailey-Hailey disease. Steatocystoma multiplex is inherited as an autosomal dominant skin condition. Multiple, smooth papules and cystic nodules are found deep in the dermis with varying size from few millimeters to twenty mm or more. They can be skin coloured. The more superficial lesions usually have a yellowish colour and a history of oily fluid expression will be noted from some of these cysts. Majority of the cysts are asymptomatic unless inflamed in which then there may be painful erythematous swelling with or without scarring.