Dermatologic Manifestations of Miliaria Clinical Presentation

Miliaria crystallina

This form usually affects neonates younger than 2 weeks and adults who are febrile or those who recently moved to a tropical climate.

Lesions appear in crops within days to weeks of exposure to hot weather and disappear within hours to days.

Lesions are generally asymptomatic.

Miliaria rubra

This form usually affects neonates aged 1-3 weeks and adults who live in hot, humid environments.

Lesions may occur under transdermal medication patches.^[3]

Lesions may occur within days of exposure to hot conditions, but they tend to appear after months of exposure.

Lesions resolve within days after the patient is removed from the hot, humid environment.

Lesions cause intense pruritus and stinging that is exacerbated by fever, heat, or exertion.

Patients may report fatigue and heat intolerance, and they may notice decreased or absent sweating at the affected sites.

Miliaria profunda

This form occurs in individuals who usually live in a tropical climate and have had repeated episodes of miliaria rubra.

Lesions develop within minutes or hours after the stimulation of sweating. These lesions resolve quickly, usually in less than an hour after the stimulus that causes sweating is removed.

The lesions are asymptomatic.

Patients may report increased sweating in unaffected skin; swollen lymph nodes; hyperpyrexia; and symptoms of heat exhaustion, which include dizziness, nausea, dyspnea, and palpitations.

A rare giant centrifugal variant of miliaria profunda has been reported in 2 infants, each at about age 3 months, who presented with symmetrical asymptomatic lesions on the trunk and extensor extremities after a low-grade fever. Unlike most forms of miliaria, the lesions in these children persisted for months.^[13]

Miliaria crystallina

Lesions are clear, superficial vesicles that are 1-2 mm in diameter.

Lesions occur in crops and are often confluent, without any surrounding erythema.

In infants, lesions tend to occur on the head, neck, and upper part of the trunk.

In adults, lesions occur on the trunk.

Lesions rupture easily and resolve with superficial branny desquamation.

See the images below.

Miliaria rubra

Lesions are uniform, small, erythematous papules and vesicular papules on a background of erythema.

Lesions occur in a nonfollicular distribution and do not become confluent.

In infants, lesions occur on the neck and in the groin and axillae.

In adults, lesions occur on covered skin where friction occurs; these areas include the neck, scalp, upper part of the trunk, and flexures. The face and volar areas are spared.

In late stages, anhidrosis is observed in affected skin.

See the image below.

Miliaria profunda

Lesions are firm, flesh-colored, nonfollicular papules that are 1-3 mm in diameter.

Lesions occur primarily on the trunk, but they can also appear on the extremities.

Lesions are transiently present after exertion or other stimulus that results in sweating.

Affected skin shows diminished or absent sweating.

In severe cases that lead to heat exhaustion, hyperpyrexia and tachycardia may be observed.

A rare giant centrifugal variant of miliaria profunda has been reported in young infants (of about age 3 mo) who presented with multiple erythematous lichenoid papules that coalesced to form infiltrated annulare and geographic plaques 1-5 cm in size with an erythematous border, located over the trunk and extensor extremities.^[13]

The following causes are recognized:

• Immaturity of the eccrine ducts: Neonates are thought to have immature eccrine ducts that easily rupture when sweating is induced; this rupture leads to miliaria.
• Occlusion of the skin, as with transdermal drug patches^[3]
• Occlusive clothing: Eighteen cases of miliaria rubra have been reported in US Army personnel who routinely wore flame-resistant army combat uniforms composed of a 65% rayon/25% Kevlar/10% nylon blend while serving in the hot, arid conditions of Afghanistan.^[14]
• Lack of acclimatization: Miliaria is common in individuals who move from a temperate climate to a tropical climate. The condition usually resolves after the individual has lived in the hot, humid conditions for many months.
• Hot, humid conditions: Tropical climates, incubators in neonatal nurseries, and febrile illnesses may precipitate miliaria.
• Exertion: Any stimulus to sweat may precipitate or exacerbate miliaria.
• Type I pseudohypoaldosteronism: This disorder of mineralocorticoid resistance leads to excessive loss of salt through eccrine secretions and is associated with repeated episodes of pustular miliaria rubra.^{[15, 16, 17]}
• Morvan syndrome: Miliaria rubra has been reported in this rare autoimmune disorder characterized by neuromyotonia, insomnia, hallucinations, pain, weight loss, and hyperhidrosis.^[18]
• Drugs: Bethanechol, a drug that promotes sweating, has been reported to cause miliaria, as have clonidine and neostigmine.^[19] Isotretinoin, a drug that affects follicular differentiation, also has been reported to cause miliaria.^[20] A single case of miliaria crystallina following doxorubicin administration has been reported.^[21]
• Bacteria: Staphylococci are associated with miliaria, and antibiotics prevent miliaria in an experimental setting.
• Ultraviolet radiation: Some researchers found that miliaria crystallina preferentially occurs in UV-exposed skin.^[22]