Miliaria Crystallina and Rubra miliaria sudamina, prickly heat, heat rash

Are You Confident of the Diagnosis?

Miliaria encompasses a group of four disorders of sweat gland occlusion at varying depths. Miliaria crystallina and rubra are a result of more superficial obstruction and are essentially benign conditions commonly seen in newborns and infants. Miliaria profunda and pustulosa result from deeper sweat gland obstruction and have greater associated symptoms and sequelae.

Characteristic findings on physical examination

Miliaria crystallina is characterized by 1- to 3- mm translucent, flaccid vesicles devoid of surrounding erythema, most commonly on the head, neck, and trunk of neonates. The vesicles are usually asymptomatic, may become confluent, and rupture easily, leaving a superficial branny desquamation without long term sequelae.

Miliaria rubra consists of 1- to 2- mm erythematous, pruritic papules or papulovesicles most commonly seen in areas of friction and/or occlusion. Lesions are nonfollicular and confluence is rare. In neonates, facial involvement is common, whereas in adults, the face is usually spared.

Diagnosis confirmation

Miliaria is a clinical diagnosis requiring little in the way of laboratory investigation. Included in the differential diagnosis of miliaria are several infectious and bullous dermatoses including herpes simplex, varicella, erythema toxicum neonatorum, neonatal pustular melanosis, childhood acropustulosis, staphylococcal infections, vesicular phase of incontinentia pigmenti (IP), and epidermolysis bullosa (EB).

Herpes simplex and varicella eruptions are distinguished by more robust serous vesicles on an erythematous base. Erythema toxicum neonatorum, neonatal pustular melanosis, and childhood acropustulosis show pustules in contrast to the vesicles of miliaria crystallina which demonstrate clear, water-like fluid.

Staphylococcal infections are characterized by larger vesicles, bullae, and pustules instead of the minute vesicles or papules of miliaria. The vesicular phase of IP presents with linear vesicles, pustules, and bullae along lines of Blaschko and is often accompanied by ocular, dental, and cnetral nervous system (CNS) abnormalities in contrast to miliaria, which is symmetric and without a distinct pattern.

EB is characterized by blister formation in response to mechanical stress. A family history of blistering disease, blister formation in areas of pressure or trauma, and lack of improvement in cool conditions should raise suspicion for EB.

Who is at Risk for Developing this Disease?

Miliaria crystallina is primarily a disorder of the neonate with a peak incidence around the 6th or 7th postnatal day. A handful of cases of congenital miliaria crystallina have been reported in the literature.

Miliaria rubra affects 0.3 – 4% of neonates, with a peak occurrence at 11 to 14 days of life, but may be seen in adults who live in hot, humid conditions.

No race or sex predilection is recognized for miliaria.

What is the Cause of the Disease?

Etiology

Eccrine ducts in newborns are relatively immature, thus predisposing to pore blockage and sweat retention. Miliaria crystallina results from superficial obstruction at the level of the stratum corneum. In miliaria rubra, the obstruction is intraepidermal, with subsequent duct rupture and leakage accounting for inflammation.

Pathophysiology

An extracellular polysaccharide substance produced by Staphylococcus epidermidis has been theorized to play a role in the pathogenesis of miliaria by occluding sweat ducts.

Systemic Implications and Complications

Extensive miliaria may rarely lead to hyperpyrexia if rest and cooling measures are not taken to counteract the state of transient anhidrosis that may accompany the disorder.

Treatment Options

Miliaria crystallina and rubra are generally self-limited conditions that resolve over a period of several days with no long-term sequelae. Treatment and prevention involves avoidance of further sweating, removal of occlusive clothing, and a few hours in a cool environment. There have been no controlled trials for topical or systemic treatment for miliaria. Oral ascorbic acid, 1 gram daily, and topical application of lanolin have been reported to be effective in adults.

Optimal Therapeutic Approach for this Disease

Prompt recognition of miliaria is of utmost importance as it may clinically resemble other more serious infectious or bullous dermatoses that can ocur in neonates. Once the diagnosis has been established, cooling measures and prevention of further sweating is indicated to prevent progression or hyperpyrexia. Improvement is generally seen over hours to days with these measures.

Patient Management

After cooling measures have been instituted (avoidance of overheating, removal of extra or occlusive clothing, cool baths, and air conditioning) monitoring is generally not indicated. Patients and family members should be counseled on the benignity of the diagnosis and lack of long-term sequelae. Follow up in 1-2 weeks to ensure resolution is wise. Adults with recurrent episodes of miliaria may be advised to relocate to a cooler climate.

Unusual Clinical Scenarios to Consider in Patient Management

No unusual clinical scenarios exist for these benign, self-limiting disorders.

What is the Evidence?

Arpey, CJ, Nagashima-Whalen, LS, Chren, MM, Zaim, MT. ” Congenital miliaria crystallina: case report and literature review”. Pediatr Dermatol. vol. 9. 1992. pp. 283-7. (This paper uses a case report to emphasis the findings in congenital miliria crystillina. It is a nice overall review.)

Ferahbas, A, Utas, S, Akcakus, M, Gunes, T, Mistik, S. ” Prevalence of cutaneous findings in hospitalized neonates: a prospective observational study”. Pediatr Dermatol. vol. 26. 2009. pp. 139-42. (Discusses the various skin findings seen in neonates that are hospatilized.)

Gan, VN, Hoang, MP. “Generalized vesicular eruption in a newborn”. Pediatr Dermatol. vol. 21. 2004. pp. 171-3. (Discussion of multiple diseases incdluding miliria.)

Haas, N, Henz, BM, Weigel, H. ” Congenital miliaria crystallina”. J Am Acad Dermatol . vol. 47. 2002. pp. 5270-2. (Short but excellent review of miliaria.)

Hidano, A, Purwoko, R, Jitsukawa, K. ” Statistical survey of skin changes in Japanese neonates”. Pediatr Dermatol. vol. 3. 1986. pp. 140-4. (Another study examining the skin findings in neonates in the hospital.)

Hindson, TC, Worsley, DE. ” The effects of administration of ascorbic acid in experimentally induced miliaria and hypohidrosis in volunteers”. Br J Dermatol . vol. 81. 1969. pp. 226-7. (Study looking at treating miliria with vitamin .)

Mowad, CM, McGinley, KJ, Foglia, A, Leyden, JJ. ” The role of extracellular polysaccharide substance produced by Staphylococcus epidermidis in miliaria”. J Am Acad Dermatol. vol. 33. 1995. pp. 729-33. (Discusses the potential role of bacteria in the development of miliria.)

O’Brien, J. ” The etiology of poral closure, I-IV”. J Invest Dermatol. vol. 15. 1950. pp. 95-152. (Discusses the pathogenesis of poral occlusion diseases.)

Straka, BF, Cooper, PH, Greer, KE. ” Congenital miliaria crystallina”. Cutis. vol. 47. 1991. pp. 103-6. (Short concise review of miliaria crystallina.)

Treadwell, PA. ” Dermatoses in newborns”. Am Fam Physician . vol. 56. 1997. pp. 443-50. (Extensive review of skin disease of the newborn.)

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