response of skin to sunlight and its contents

I

II

I

I

Photobiology of melanin pigmentation: Dose/response of skin to sunlight and its contents Madhu A. Pathak, M . B . , P h . D . , * and Dan L. Fanselow, Ph.D.**

Boston, MA, and St. Patti, MN A randomized double-blind clinical trial involving twenty-two voltmteers was conducted in two locations (Orlando, FL, and St. Paul, MN) to test the efficacy of the newly designed ultraviolet monitor badges (Sun Timers), described in another paper by us in this issue of the JOtJRNAL, ~ and to establish the relationship between spectral band exposure dose and the biologic responses of erythema and pigmentation. Individuals with skin types II, III, and IV, exhibiting differences in reactivity to solar radiation, were exposed to varying doses of full-spectrum sunlight through templates mounted on the lower portion of the back. Simultaneously, on the upper portion o1" the back, the same volunteers were exposed ttu'ough two different types of polyester filters that transmitted ultraviolet A (UVA) and visible radiation. Using templates with windows, exposures to full-spectrum sunlight, UVA, and visible radiation were carried out to I, 2, 3, 6, and 9 sunburn units (approximately 30-270 millijoules/cm ~ between 10:30 A.M. and 3:30 I,.M. daylight time in mid summer), measured with the aid of a Robertson-Berger meter and an ILT00 International Light radiometer. Erythema and pigmentation resulting from these exposures were graded (double-blind) immediately after exposure, at 24 hours, and after 5 days. Numerical skin respon~ ratings at each exposure dose for different spectral bands were then averaged and plotted. It was found that the U VB monitor response was predictive of a 24-hour erythema response and 5-day pigmentation response within 30% of the biologic average for skin types II, III, and IV. U VA radiation stimulated melanogenesis. The minimal melanogenic dose (MMD) for skin type II was the same as the minimal erythemogenic dose (MED). The MMD for individuals of skin types 11I and IV was distinctly less than their MED. Thus, melanogenesis can be stimulated with a suberythemal dose of UVB or UVA radiation. The sun protection factor values of melanin for melanized skin have been estimated to vary fi'om 1.0 (skin type II) to 4.3 (skin types V and VI). (J AM ACAD DERMATOL 9:724-733, 1983.) From the Depm-tment of Dermatology,* Harvard Medical School and Massachusetts Genera/ Hospital, Boston, and Personal Care Products Department,** 3M Company, St. Paul. Partially supported by grants in aid from the 3M Company. St. Paul, MN, and by the U.S. National Cancer Institute, Department of Health, Education, and Welfare, Bethesda, MD, Grant No. 2-R01-CA-05003-24. Accepted for publication May 19, 1983. Reprint requests to: Dr. Madhu A. Pathak, M.B., Ph.D., Department of Dermatology, Warren 5, Rm. 562. Massachusett~ General Hospital, Boston, MA 02114.

724

The ultraviolet spectrum o f sunlight is generally classified into three wavelength regions on an arbitr,'uy basis, based on certain well-recognized biologic effects: (1) UVA (320-400 nm), the region that induces both immediate tanning reaction (pigment-darkening reaction) and the delayed tanning reaction or tree melanogenesis. This spectrum is now widely used in the treatment of psoriasis with oral psoralen (PUVA) therapy. (2)

Volume 9 Number 5 November, 1983

Photobiology of melanin pigmentation 725

Table I. Spectral distribution of radiation reaching skin surface--optical filter experiment Wavelength (nanometers)

292 295 300 305 310 315 320 325 330 340 350 360 370 380 390 400 420 440 450 460 470 48O 490 500 550 600 700

Full spectrum*

Left filter UVA+ visible radiation only

0.0019 0.0052 0.0190 0.046 0.072 0.12 0.16 0.23 0.25 0.28 0.30 0.36 0.39 0.39 0.48 0.72 0.77

0 0 0 0 0.022 0.029 0.090 0.150 0.18 0.22 0.25 0.31 0.35 0.35 0.45 0.68 0.74

0.97

0.95

1.00 0.93 0.81 0.55

1.00 0.93 0.81 0.55

I

[ I

Right filter UVB+ visible radiation only

[

Center filler visible radiation only

0.0013 0.0046 0.020 0.045 0.064 0.085 0.090 0.085 0.045 0.0090 0.0009 0.00009 0 0 0 0 0 0 0.06 0.I1 0.20 0.40 0.70 1.00 0.93 0.81 0.55

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.025 0.10 0.30 0.56 0.83 tAX) 0.93 0.81 0.55

*Normalized values; arbitrary units abstracted from Pettit E: Astrophysics J 75:217, 1932.

Mid-range UVB (290-320 nm), the principal sunburn-producing region of the solar spectrum that causes delayed, long-term tanning, is also largely responsible for keratosis, skin cancer, and actinic elastosis (skin aging). (3) Wavelength region shorter than 290 rim, referred to as UVC (200-290 ran), the high-energy component that is screened out by the ozone layer and is, therefore, absent from the solar spectrum reaching the earth. 2 This spectrum of radiation is, however, present in certain artificial light sources (germicidal radiation). Based on the reactivity of the skin to solar radiation, individuals are classified into six different skin types, a-'~ A normal person of skin type lIl or IV, when exposed to the sun, exhibits first an immediate pigment darkening (IPD) reaction within 5 to 15 minutes, which reaches its maximum intensity after 60 to 90 minutes of sun exposure, then a delayed erythema (sunburn) reaction after 3

to 12 hours, with maximum intensity at 20 to 24 hours postexposure, and, finally, a delayed tanning reaction (melanogenesis) with a maximum pigmentation response at 5 to 7 days postexposure ?-4 Sunburn and delayed tanning (DT) are optimally induced by UVB radiation. UVA radiation is also erythemogenic and melanogenic, but less so than U V B ) (1 MEDuvB = 30 millijoules/ cm"; 1 MEDuvA = 30,000 millijoules/cm 2 or 30 joules/era 2.) IPD reaction involves the oxidation of preexisting melanin in skin and is induced by 320 to 700 nm radiation, with a maximum effect between 320 and 380 nm. Thus solar radiation is a wellrecognized stimulus to increase melanin pigmentation in human skin. The magnitude of the response is believed to be related to the genetically determined functional capacity of melanocytes. In

Journal of the

726

Pathak and Fanselow

Americt~n Academyof Dermatology

Figs. 1-7. For legends, see opposite page.

Volume 9 Number 5 November, 1983 general, individuals with darker skin (skin types IV to VI), genetically endowed with greater constitutive pigmentation, exhibit greater ability for induced tanning (facultative pigmentation) after ultraviolet or other stimuli. After single or repeated UVB or UVA irradiation of skin in humans or laboratory animals (mice and guinea pigs), an increase in the number of functioning melanocytes, an increase in the size of perikaryon and in the branching (arborization) of dendrites, an enhancement of tyrosinase activity, and an increase in the size and number of melanosomes in both melanocytes and keratinocytes have been reported? Although many specific aspects of melanocyte function have been shown to be increased by ultraviolet radiation, our knowledge of the familiar DT reaction is still limited. As yet, we do not know if the absorbed photons directly affect a receptor in melanocytes or if increased melanogenesis results from specific response to ultraviolet-induced deoxyribonucleic acid (DNA), ribonucleic acid (RNA), or protein (enzyme) injury in melanocytes or keratinocytes or both. We do not yet know the relative quantum efficiency and MMD of UVA, UVB, and U V C radiation for different types of individuals (skin types l to VI). We have limited information on solar UVB and UVA doseresponse curves for DT. In the previous paper, ~ we described the 24hour erythema dose/response characteristics of individuals of skin types II, 11I, and IV exposed to full-spectrum sunlight. In the study described here, the dose/response to individual components of sunlight is examined and compared with full spectrum. Emphasis is placed on the melanogenic potential of the UVB and UVA spectrum. MATERIALS A N D M E T H O D S

This study was conducted as part of the double-blind UV monitor efficacy study (Orlando, FL, and St. Paul,

Photobiology of melanin pigmentation

727

MN) described in the previous paper.~ The twenty-two voltmteers and experimental conditions were the same. Two pre-cut, flexible, adhesive-backed, microfoam tape templates with ten -~x-~-inch windows were adhered to the lower portion of the back of each volunteer (Fig. 1). These templates were used for fullspectrum sunlight exposure. This portion of the experiment produced both erythema and pigmentation data; the erythema data have been presented, j and the pigmentation data are interpreted here. In addition, a template/optical filter assembly was adhered to the upper portion of the back of each volunteer. This assembly contained three filters positioned over three exposure templates, so that each of the three areas was exposed to sunlight of a different spectral quality. The filter on the left in Fig. 1 transmitted UVA + visible radiation only (_310-760 nm), the filter on the right, UVB + visible radiation only (290-300 and 450-760 nm), and the filter in the center, visible radiation only (450-760 nm). The spectral distribution of the radiation reaching the skin at the four test sites of the back is given in Table I (Air Mass 1). In the filter unit, template and filter were fixed at one end. Once the template was adhered to the back, it would remain in place; the filter flap could be lifted to get at the template to cover the squares. The perimeter of the filter flap was lined with 1 89 pieces of 88 black rubber tubing, staggered to provide a light baffle, but allowed forced air circulation. To prevent perspiration fogging, units were force-ventilated by drawing air through with a high-speed vacuum. Volunteers lay in the sun in a prone position; the upper portion of the back and the lower back areas, with prefixed templates, were exposed to solar radiation for varying doses. The ultraviolet monitors (Sun Timers), Robertson-Berger meter, and International IL700 radiometer equipped with UVB detecting probes simultaneously measured UVB radiation for doseresponse curves. At intervals of approximately 1,2, 3, 6, and 9 sunburn units of full-spectrum sun exposure, as determined by the UVB monitors, windows of each template were covered with pieces of the ultraviolet-opaque mi-

Fig. 1. Layout of exposure templates. Lower portion of back--full-spectrum exposure templates. Upper portion of back--template/optical filter assembly (spectral distributions are listed in Table I). Left filter. UVA + visible transmitting; rightfilter, UVB + visible transmitting. Figs. 2-4. Skin responses following sun exposure of skin type II individual (immediately, at 24 hr, and at day 5 after exposure). Figs. 5-7. Skin responses following sun exposure of skin type III individual (immedi.ately, at 24 hr, and at day 5 after exposure).

728

.loumal of the American Academy of Dermatology

Pathak and Fanselow

~.0

i

3.5

t

i

t

i i I I

i

i

I

I

F U L L SPECTRUM (SKIN TYPE II)

30

!

"" /'~/ /////!

.

i

i

i i i qll

OVA ONLY (SKIN TYPE II)

-:"

,.~"

2.5

i

i i ir //

3.0

."-Q~'~"i ././""

/g g//./

r. L%~Eio_,/Etyt~m_E

8

I=" 2.0

/' / /

,9

5 Day P omenlo ion

I ............. Immediate Pl~lmenlotion

1.5

/

9

i.~, .oo, ~,~..... ,,oL 0.5

i

,7

l,tlp ~,

I

r.s

//

L

~

,,! ,~ /' ?"

ill I

/

.T

i l

J[,

~ 2.5 13~ 2.G

I II /~

Ix 24 Haul Erythemo

n,-

.~.I_

.

~'g"/

Immed'ote _ _ _ ::_ _ _Er:.Y.lhemo ....

9 5 Oily Pigment(Ilion ,,..4

I.G

... I

9 Immediate Pigmenlatton

9"'~"

I

~

4

4 ''~

9 UVA Exposure ([oule~l/cm 2)

5 6Jr~l~

Exposure (Sunburn Units)

Fig. 8. Dose/response for exposure of skin type el volunteers to full-spectrum sunlight (average values, Orlando data).

~"

.:....~f~

9 z4 Ha., ff,g,.]a.to.,o. 0.5

2

.j

z~_H~rEjy_,,j?o__

lib

27

Fig. 9. Dose/response for exposure of skin type II volunteers to sunlight filtered to transmit UVA + visible radiation only (responses to exposures made simultaneously to the full spectrum tire shown in Fig. 8).

T a b l e I I . Pigmentation rating system

Assigned numerical rating

Visual rating

UVB ONLY (SKIN T Y P E II)

3.0

Pigmentation

/ 4/ /

// 2.5

0 1 2 3 4 5

0 +_+ ++ +++ ++++

None (exposed skin matches unexposed skin) Trace pigmentation Light brown Moderately brown Dark brown (chocolate) Deep violaceous brown or black

crofoam tape (four randomized windows for each fullspectrum exposure, two for each filtered exposure). Windows were closed at precisely the time dosimetry readings were taken, with each volunteer being read and taped individually. After all exposure windows had been closed (approximately 4-hours' exposure), the volunteers were taken inside for evaluation of immediate erythema and immediate pigment darkening (IPD) reaction. They were recalled the following day (after 20 hours) and at 5 days for assessing the degree of erythema, edema, and pigmentation. Ratings were assigned in a double-blind manner according to the criteria listed in Table I1. The numerical skin response ratings were averaged for each exposure and plotted against the logarithm of exposure (as recorded by the UVB monitor) for each volunteer. From these plots, response ratings were taken at exposures of 1,2, 3, 6,

2.0-

I " Immedit'He . . . . . . . Erylhemo . . . . x 2 4 Hour Erylllemo . . . . . . . . . 9 5 Day P=gmentOhon

] // /

.............

~"

~

,

=. Immediate Pigmenloho

1.5

,'

ii

/

/ /

// / /

./

I .i~~

/ ../.~j

[= z4 Hour p.qme.,o,~

i

.Y

1.0

/ //~t// ,///.//

05 l

l

'

'

UVB

l~

'

'~

Exposure

30

// ~o

9~o ,zo'

' ''

(millijoules/cm z)

Fig. I0. Dose/response for exposure of skin type I1 volunteers to sunlight filtered to transmit UVB + visible radiation only (responses to exposures made simultaneously to the full spectrum are shown in Fig. 8). and 9 sunburn units, grouped according to the interview-determined skin types, and averaged. RESULTS Typical skin responses (immediate, 24-hour, and 5 days after exposure) for two of the individuals (one of skin Type II and the other of skin Type III) are shown in Figs. 2-7. Average fullspectrum dose-response curves for the five-rated skin reactions (immediate erythema and pigmenta-

Volume 9 Number 5 November, 1983

Photobiology of melanin pigmentation 729

4.0

~'

r

I

[

I

DEEP BROWN (CHOCOLATE

1 I 1 1

I

I

/

Z >" m r

3.0

MODERATELY BROWN

/

m

i

l:,R,g#g 2.0

/

,I

I . L,.-'F I

4.0

/"

,/

/ 3.0

i111~.~.

SKIN TYPE it

ill

/

/

I

LIGHT BROWN

m

/

Z

tu Z

r W

~ 2.0

7<

i. ul m O

5 DAY PIGMENTATION

/

O 1.0

TRACE PIGMENT

I.O

tll

/ / / / I .3

I .4

11111

I 2

.6 .7 .11.g 1.0

I 3

I 4

I I I I I w 6 7 II II

EXPOSURE DOSE ( S U N B U R N UNITS)

Fig. II. Dose/response curves for 24-hour delayed erythema reaction and 5-day pigmentation response (melanogenesis) in individuals of skin type II who burn easily and tan minimally. 4.0

I

I

1

~" DEEP BROWN (CHOCOLATE)

I

I

I

I I I

I

I

I

I

I

:3.0

I

4.0

3.0

MODERATELY BROWN SKIN TYPE III

! I

I

/I

Z < n-

I

2.0

I

III/I

LIGHT BROWN #

In .i

PIGMENTATION

It! 2.0

I

/

tt

// ERY'THEMA 1.0

TRACE ~GMEHT

1.0

l/jill /

W X"

I

.3

1

I

I

~i(l

I

I

~"

I

I

.4 .5 .8 .T .8 .111.0 2 3 E X P O S U R E DOSE ( S U N B U R N UNITS)

I 4

I S

1 6

I I 7 8

Fill. 12. Dose/response curves 1"oi"24-hour delayed erythema reaction and 5-day pigmentation response (melanogenesis) in average individuals of skin type II[ who burn moderately and tan moderately, and uniformly (light brown). tion, 24-hour erythema and pigmentation, and 5-day pigmentation) of type lI volunteers are plotted in Fig. 8 (Orlando data). These are contrasted with the UVA responses (Fig. 9) and the UVB responses (Fig. 10). For full-spectrum sunlight (a

composite of UVA and UVB), exposures are expressed in sunburn units (one sunburn unit is equivalent to 30 millijoules/cm'-' of UVB radiation). UVA exposures are given in joules/era'-', and UVB in millijoules/cm'-'. The average 5-day de-

730

Journal of the American Academy of Demaatology

Pathak and Fans'elou"

4,0

i

I

i

i

I

4.0

1

~" DEEP BROWkl (CHOCOLATEI

r

3.0

3.0

MODERATELY EROWN

d*/I//II

SKIN T~fPEIV

m ae

2.0

LIGHT BROWN

r LU pIOtaENTATION

i

1.0

9

TRACE I:IGMENT

9

/

/

t. er

iiii

2.0

i

ERYTHEMA / 1.0

/ /

//

/

/

/ I

.2

I

.3

I

.4

.5 .4 .7 .11.91.0

[

2

,''

I

3

I

4

I

5

I

I 1

B ? I

EXPOSURE DOSE (SUNBURN UNITS)

Fig. 13. Dose/response curves for 24-hour delayed erythema reaction and 5-day pigmentation response (melanogenesis) in individuals of skin type IV who burn minimally but always tan well (moderate brown). Table IV. Ratio of U V A exposures required to generate a 2.0 ( + ) 5-day pigmentation response (full specmtm and U V A alone)

T a b l e I r l . 5-day pigmentation response as a function of exposure Average response at:

+++++I [ I I I type

old

I MED

2 MED

3 MED

[I 0,80 0.60 1.7 Ili 0.71 0.60 2.0 IV 0.50 0.70 1.4 Percent of panelists within 30% II 67 33 100 llI 72 0 100 IV 0 0 100

6MED

9MED

2.3 2.7 2.8 2.6 3.2 3.2 2.1 2.8 3.9 of above values 100 100 67 100 100 100 100 100 100

layed pigmentation dose/responses for individuals of skin types II, IIl, and IV are summarized in Table lII, with the percentages of volunteers from each skin type showing good agreement within 30% of the average value for that skin type. Except in the one MED or onset region, nearly all of the volunteers' pigment response readings fell within the biologic average for their assigned skin type. The 5-day pigmentation response as a function of ultraviolet exposure dose (totat spectrum) for individuals of skin types [I, II[, and IV is presented separately in Figs. 1 l - I 3 , together with the 24-hour erythema response curves. To illustrate

UVA exp()sure in presence of UVB UVA exposure alone

Skin type I/ III IV

I

Ratio 0.24 0.53 0.71

the melanogenic potential of UVA plus UVB spectrum and UVA alone, the 5-day pigmentation response is plotted as a function of exposure dose (joules/era'-') for the three skin types in Figs. 14-16 for both UVA alone, broken line, and UVA in the presence of UVB (full spectrum, solid line). UVA exposures required to produce a + pigmentation (light brown) response with and without UVB were taken from these plots. The ratios of these two exposures are given in Table IV for the three skin types. There was no detectable pigment response to visible light other than a minor immediate reddening that is attributed to heat. The derived values of the MED and the minimal melanogenic dose (MMD) for skin types II, I11,

Volume 9

Photobiology qf melanin pigmentation

Number 5 November, 1983

35

30

t

3.C

5 DAY PIGMENTATION (SKIN TYPE II) ~ -

I'

I

J I I I

/ /T /

I

I

5 DAY PIGMENTATION (SKIN TYPE IV)

Jl

Illl 11/''3 /

IO

I

~,.,,

25

15

I

731

1.0

/i!

//

13

IS3 IS3

[ UV~/}'I~

I

0.~

05

[ 3

4

5

6

7

Exposure

I0 (joulos/cm

ZO

50

40

I 3

L/

I

I

f r I I

,, ~,, ,o ~'~ Exposure(joules/cm2)

2)

20 20

Fig. 14. Five-day pigmentation response versus UVA

Fig. 16. Five-day pigmentation response versus UVA

exposure for skin type I1. Solid line, In the presence of UVB (full spectrum); hroken line, UVA alone.

exposure for skin type IV. Solid line, In the presence of UVB (full spectrum); broken line, UVA alone.

I

3.5 3.0

I

!

I

I

I

I 11

I

I

I

Table V. Minimal erythernogenic dose and minimal rnelanogenic dose for individuals of skin types I1, 11[, and IV

I

5 DAYPIGMENTATION (SKINTYPE7 / / / /

Minimal erythema dose

2.5

Y

(MED)

I.,5

1.0 0.5 3

4 5 6 7

tO

20

1

30 40

I

I I I

Exposure (joules/era~')

Fig. 15. Five-day pigmentation response versus UVA exposure for skin type III. Solid lilw, In the presence of UVB (full spectrum); broken line, UVA alone. and IV (obtained from the data presented in Figs. 11-13) are shown in Table V.

DISCUSSION Certain interesting interpretations and general conclusions can be made from the data presented in this paper as well as in the preceding paper.t It appears that: (1) The UVB monitors (Sun Timers) provide a reasonably reliable measure of the ultraviolet exposure dose for the lay person (Table lI[). (2) The 24-hour erythemal response for individuals of skin types II, III, and IV is linear up to six MED exposure values. The delayed pigmenta-

Minimal melanogenic dose (MMD)

Skin type

RB SBU*

Mill/joules/cm ~

RB SBU*

MilIijoules/era ~

II III IV

0.7 1.2 2.6

21 36 78

0.8 0.7 0.5

24 21 15

*RB SBU values arc expressed in sunburn units (Roberlson-Berger meter).

tion response is also dose-related and is linear up to at least six MED exposure values. (3) Individuals of skin type II have the lowest MED, whereas individuals of skin types III and IV exhibit high MED values. (4) The classification of individuals into skin types I, II, III, IV, etc., as originally outlined by our laboratory, s is certainly helpful in determining the sun-reactivity and skin responses of different individuals. (5) The MMD is the same as the MED for individuals of skin type II, whereas the MMD for individuals of skin types III and IV is distinctly less than their MED. Thus, increased melanogenesis (tanning) can be achieved with suberythemal exposure doses of solar radiation. The dose/response curves for erythema and pigmentation are interesting. All three skin types

732

.lournal of the Amellc,m Academy of Dermatology

Pathak and Fans'elow

showed ultrawolet dose-dependent delayed (24hour) erythema response charactenstms (Figs 11-13) For each skin type, this response was hnear over the same relative response range, dlffe~mg only m threshold value and saturatmn exposure We attribute the d~splacement between the dose/24-hom erythema response curves fol skin types II, Ill, and IV to differences in the consmut~ve pigmentation of these three skin types This ts ewdent from the MED values in Table V Volunteers of skin types II, [lI, and [V exhibited MED values of 0 7, 1 2, and 2 6 sunburn umts, equivalent to 21 0, 36 0, and 78 m~lh.loules/cm-' ~espect~vely If one assumes that the regional thickness of the stratum corneum and vmble epidermis of tim unexposed skin at the scapular and mfiascapula~ regions of the back ts the same ~n m&vtduals of skin types 1.[, III, and IV, then the obsm ved &ffe~ences m skin responses in terms of MED values and the degree of erythema reaction appem to be due to the photoprotect~ve role of constittmve melamn p,gmentatmn The MED data presented m Table V and ~n Figs 11-13 do suggest that melanin acts as a photoprotect~ve polymer The protection index of melamn (i e , sun ptotectmn factor) as determined by the MED value varies w~th skin types, ,t ranges fiom 1 0 for skin type II to 1 7 for skin type 1I[, and to 3 7 for skin type IV Although not shown m Table V, our observations of MED values determined m md~wduals of skin types V and V[ suggest that the melamzed skin of these ~ndlvlduals prowdes a sun p~otectmn factor between 4 3 and 5 Whether or not the IPD reacuon had any photoprotectlve effect on the observed differences m the MED values could not be ascel-ta~ned The IPD reactmn in the Orlando experiment was greater than m the St Paul experiment, but the 24-hour erythema dosehesponse was singular in both experiments suggesting that the [PD has a minimal photoprotectlve effect in m&wduals of skin types II and Ill, m md~vlduals of skin type IV, however the [PD reaction did contribute to photoprotectton (F~g 13) The 5-day p~gmentatmn response was doserelated and also reasonably predictable For skin

type II, the MMD was approximately the same as the MED dose (Table V) For skin types III and IV, the MMD was lower than the ezythemogemc dose Tilts ~ndmates that melanogenes~s can be sumulated with a suberythemogemc dote of U VB or solar radmt~on Optical filter expermaents also provided some mteresung findings The full-spectrum dose/ response of type II individuals is ,llustrated in Fig 8 The similarity m slope of the Immediate erythema, 24-hotu eiythema, and 5-day pigmentation response suggests that the three have basically a common mechanism (~ e , they appear to be medl,ited by the tnttt,tl event of celhtlat damage) Dose/lesponse of skin types lit and IV shows a sttmlai agleemcnt between these three lesponses

The UVA component wits nonm ythemogemc up to 25 joules/cm" (F~g 9) Howevm, m the same range, there was substantml 5-day ptgmentatmn genmated m all thlee skin types (F,gs 14-16) Flora the data one can conclude (1) UVA rachatlon ~s melanogemc (stimulates the formatmn, melamzatlon, and t~ansfer of new pigment granules) (2) Exposure of skin to UVA alone, up to 25 joules/era" is nonerythemogemc (3) Melanogenesls occurs at doses well below the erythemogemc doses in all throe skin types (4) The combined melanogcmc effect of UVA + UVB is greater than UVA alone Figs 11- 16 and Table 1 V suggest that for higher skin types (III and IV), UVA ~s an important and major contributor to the snmuiat~on of melanogenesis whereas in individuals of type I1, UVB l~ the primary contr~butol to melanogenes~s Figs 8 and 9 show that the UVA component ~s more capable of oxidizing the preexisting pigment than the UVB component, pmhaps due to deeper penetratmn of UVA than UVB into skln Secondly, the darkemng ~s maximum lmmedmtely after exposure and xs minimum at 24 hours This suggests that the tedox syqtem of melanin polymer tends to reduce the oxidized pigment w~thm 24 hours, and the residual plgmentatlon observed at 24 hours is the result of UVA-mduced re&st~lbut~on of the melanosomes within the basal and suprabasal kelat~nocytes ~ ~

Volume 9 Number 5 November, 1983 Our special thanks are conveyed to Francille MacFarland, M.D., at the Department of the Navy, Naval Hospital, Orlando, FL, to Eric Werner Kraus, M.D., at the Brooke Army Medical Center, Demmtology Service, Fort Sam Houston, TX, for providing us with assistance and excellent facilities to c,'u'ry out the field trials, and to Ms. Becky Britz of 3M Co. for the artwork,

REFERENCES I. Fanselow DL, Pathak MA, Crone MA, et al: Reusable ultraviolet monitor: Design, characteristics, and cfficacy. J AM Ac~,o DERM,','roL9:??, 1983. 2. Parrish JA: The scope of photomedicine, in Reagan JD.

Photobiology ( f melanin pigmentation

Parrish JA, editors: The science of photomedicine. New York, 1982, Plenum Press, pp. 1-17. 3. Pathak MA: Sunscreens: Topical and systemic approaches for protection of human skin against harmful effects of solar radiation. J AM Ac^o DERMATOI.7:285-312, 1982. 4. Pathak MA, Jimbow K. Fitzpatrick TB: Biology of pigment cell, in Seiji M, editor: Pigment cell 1981, phenotypic expression in pigment cell, Proceedings of X1 International Pigment Cell Conference, Sendal, Japan. 1980. Tokyo, 1981. University of Tokyo Press, pp. 655670. 5. Pathak MA, Jimbow K, Szabo G, Fitzpatrick TB: Sunlight and melanin pigmentation, in Smith KC editor: Photochemical and photobiological reviews. New York, 1976, Plenum Press, vol. 1, pp. 211-239.

Infantile acropustulosis* J. L. J e n n i n g s , Lieutenant, M C , U S N R , and William M . B u r r o w s , Captain, MC, U S N San Diego, CA Infantile acropustulosis (IA) is a syndrome characterized by recurrent crops of 1- to 2-ram intensely pt'uritic vesicopustules that are found primarily on the distal extremities of infimts. It is reportedly responsive to sulfones and unresponsive to other therapy, but if left untreated spontaneously resolves at about 2 years of age. It is more common in black male patients. The histopathologic findings and clinical course are distinct. (J AM ACAD DERMA'VOI. 9:733-738, 1983.)

Since the initial reports o f infantile acropttstulosis (acropttstulosis o f infancy) (IA) in July, 1979, by Jan'att and R a m s d e l l ~ and Kahn attd Rywlin,~ there has been no further m e n t i o n of this From the Department of Dermatologyand the Clinical Investigation Department. Naval Hospital. Accepted for publication Feb. 15, 1983. Reprint requests to: Lieutenant J. L. Jennings, MC. USNR. Clinical Investigation Department, Naval Hospital, San Diego, CA 92134. *The opinions or assertions contained in this paper are those of the authors and are not to be constrned as official or as necessarily reflecting the views of the Department of the Navy or the naval service at large.

disorder in the literature. O v e r the p a s t y e a r , we have had the o p p o r t u n i t y to e v a l u a t e and follow four infants with IA (Table I). The f o l l o w i n g case studies and review o f the literature are intended to better define and e m p h a s i z e this derrnatosis as a distinct c l i n i c o p a t h o l o g i c entity ( T a b l e II).

CASE REPORTS Case 1 This 17-month-old black male child presented to our clinic with a 9-month history of an extremely pruritic vesicopustular eruption of the distal extremities unresponsive to either Kwell or 1% hydrocortisone cream.

733