Disorders of Eccrine and Apocrine Glands

32

Disorders of Eccrine and Apocrine Glands

Eccrine and apocrine glands represent the two major types of sweat glands (see Fig. 91.1).

Eccrine Glands

• Functional from birth and activated by thermal stimuli via the hypothalamic sweat center; while their major function is thermoregulation by evaporative heat loss, they are also activated by emotional stimuli.

• Innervated by sympathetic fibers that have acetylcholine as their major neurotransmitter.

• Generalized distribution, with greatest concentration on the palms and soles.

• The eccrine duct opens directly onto the skin surface, and the excretory product is a clear hypotonic fluid that is mostly water but also contains NaCl.

Apocrine Glands

• Unclear function in humans; functional development requires androgens.

• More limited distribution – primarily axillae, nipples/areolae, and umbilical and anogenital regions; modified apocrine glands are found in the external auditory canals and eyelid margins.

• The apocrine duct drains into the superficial portion of the hair follicle (see Fig. 91.1).

• ‘Decapitation’ of apocrine gland cells produces an odorless and viscous fluid; however, its degradation by flora on the skin surface can lead to an odor.

Hyperhidrosis

• Excessive production of eccrine sweat is usually due to primary cortical (emotional) hyperhidrosis and the favored sites are the axillae or palms and soles (Fig. 32.1) > the face (Fig. 32.2); involvement is bilateral and symmetric.

Fig. 32.1 Volar hyperhidrosis (primary cortical). The palmoplantar skin displays excessive eccrine sweat production, including the portions that extend onto the sides of the hands, feet, and digits. Its onset is during childhood as opposed to axillary hyperhidrosis, which has its onset around puberty.

Fig. 32.2 Primary cortical (emotional) hyperhidrosis involving the face. Sweat droplets are evident on the upper cutaneous lip, jawline, and chin. Reproduced from Hurley HJ. Hyperhidrosis. Curr. Opin. Dermatol. 1997;4:105–114. Philadelphia: Rapid Science Publishers.

• Secondary cortical hyperhidrosis is associated with genodermatoses, including palmoplantar keratodermas and epidermolysis bullosa simplex; associated odor reflects maceration and degradation of keratin by bacteria.

• Secondary hypothalamic (thermoregulatory) hyperhidrosis can be due to a number of systemic diseases, from infections to neoplasms (Table 32.1).

Table 32.1

Causes of secondary hypothalamic hyperhidrosis.

CNS, central nervous system; CVA, cerebrovascular accident; MAOI, monoamine oxidase inhibitor; RSD, reflex sympathetic dystrophy, also referred to as complex regional pain syndrome; SSRI, selective serotonin reuptake inhibitor. Linezolid is an MAOI.

• Secondary medullary (gustatory) hyperhidrosis can be physiologic as exemplified by the facial sweating that occurs with spicy foods or pathologic as occurs in Frey’s syndrome (Fig. 32.3); in the former, taste receptors send afferent impulses, whereas in the latter, disrupted nerves for sweat aberrantly connect with nerves for salivation.

Fig. 32.3 Gustatory sweating in the auriculotemporal (Frey’s) syndrome, as a consequence of parotid surgery. The blue-black area represents sweating (starch–iodine technique). Salivary stimulation induced this sweating response. Reproduced from Hurley HJ. Hyperhidrosis. Curr. Opin. Dermatol

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Apr 22, 2016 | Posted by admin in Dermatology | Comments Off

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