“Panting sign” as a clinical clue to heat stress in hypohidrotic ectodermal dysplasia

A 1-year-old male child, born of a non-consanguineous marriage, presented with sparse scalp hair and the absence of dentition since birth. Clinical examination revealed anhidrosis, an underdeveloped mandible, and thick, everted lips [Figure 1a]. The nails were normal. The starch-iodine test revealed a complete absence of sweating. There was no family history of similar complaints in a three-generation pedigree chart.

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Figure 1

(a): Sparse hair and everted lips in the patient of hypohidrotic ectodermal dysplasia; (b): Panting-like, non-labored open-mouth breathing with tongue protrusion.

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The parents also reported a recurrent pattern during heat exposure or physical exertion: The child would become uncomfortable, protrude his tongue, and develop rapid, non-laboured open mouth breathing (panting-like breathing) [Figure 1b].

Dermoscopic examination of the chest demonstrated marked reduction of pinpoint white dots (eccrine duct openings/“pores”), supporting a diagnosis of hypohidrotic ectodermal dysplasia (HED) [Figure 2]. Genetic testing was not performed due to the financial constraints of the parents. Dermoscopy thus served as a useful, non-invasive adjunct to substantiate hypohidrosis in the absence of molecular confirmation.

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Figure 2

(a): Marked reduction of pinpoint white dots (eccrine duct openings/“pores”) on dermoscopy; (b): Normal dermoscopy (black arrow shows the normal eccrine opening, blue arrow shows follicular opening with vellus hair) (Heine Delta 30, polarized mode, 10x).

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Conventionally, panting is regarded as a thermolytic strategy in non-human mammals, allowing evaporative cooling from the upper respiratory tract in the absence of sweating. This behavior is not seen in humans. However, emerging literature indicates that thermal panting may also occur in hyperthermic humans, particularly those with impaired sweating, such as patients with HED or spinal cord injuries, but does not confer a physiologically significant thermoregulatory benefit.^[1,2] Accordingly, in anhidrotic states such as HED, panting-like breathing should be viewed primarily as an observable clinical marker of heat stress rather than a reliable compensatory cooling mechanism.

We propose that recognition of a “panting sign” in an infant or young child – particularly when triggered by heat or exercise – should prompt clinicians and caregivers to consider HED and other anhidrotic disorders, and to institute immediate cooling and preventive counseling. Standard anticipatory guidance includes strict heat avoidance, access to a cool environment and water, external cooling during exertion, and urgent evaluation for lethargy, altered sensorium, or persistent fever, given the risk of hyperthermia in HED.^[3]