Discuss the pathogenesis of miliaria pustulosa.

All forms of miliaria result from the retention of sweat secondary to occlusion of the sweat ducts. The pathogenesis of miliaria pustulosa is not entirely understood, but it is believed that heat and occlusion result in the proliferation of surface bacteria that produce toxins that damage the acrosyringium (intraepidermal portion of the eccrine sweat duct). Depending on the level of occlusion, different patterns of disease are produced. If significant numbers of neutrophils are attracted to the acrosyringium, a flaccid pustule develops, producing miliaria pustulosa. If the disease is less severe or the inflammatory response muted, then only an erythematous papule is present, producing the clinical lesion called miliaria rubra (heat bumps, prickly heat). If the damage to the acrosyringium is entirely mechanical, such as occurs following a sunburn, the inflammatory response is minimal and small superficial vesicles are formed at the acrosyringium, producing the variant referred to as miliaria crystallina.