R ev i ew Psoriasis <!f the nails and scalp 
Psorias-is of tlie nails and scalp 
C. Misciali, B .M. Piraccini and A. Tosti 
S UM M ARY 
About 50% of patients with psoriasis present involvement of the nails and/or the scalp. Psoriasis limited 
exclusively to these regions is not rare. Koebner phenomenon can at least partially explain the localization 
of psoriasis in these areas, which are continuously exposed to traumas. Manual work and pedal 
biomechanics are responsible far repetitive micro traumas to the fingernails and the toenails, respectively, 
while brushing and combing cause traumas to the scalp. 
Although the histological findings of nail and scalp psoriasis are very similar to those of psoriasis of the 
glabrous skin, the clinical manifestations are substantially different, reflecting the particular anatomy 
and physiology of these regions. 
Scalp psoriasis 
Clinically, localized e1ythematous and scaly papules 
or p laques of scalp psoriasis are similar to those of skin 
psoriasis. Early lesions are often confined to the occipital 
area. Fully developed lesions show masses of heaped 
scales and a solicl cap, which extencls just beyond the 
hair margin. Involvement of the whole scalp can occur 
(1, 2) (Fig. 1) . 
Psoriatic scalp scales are gray, firm ancl thicker than 
those of other body regions; these can sometimes detach 
from the scalp and lay around the hair shafts as tubes 
(pseudo hair-casts) (3) . 
Occasionally, sca lp psorias is is associated w ith 
itching (1, 2). 
Psoriatic alopecias 
Telogen effluvium can accompany scalp psoriasis; 
it usually improves w hen the disease iS in remission C 4, 
5). Sometimes telogen effluvium is acute but more often 
it has a chronic cou rse . Its pathogenes is coulcl be 
explained by psoriatic inflammatory cells that elicit 
cytokines. This phenomenon interferes with the normal 
growth cycle cau~ing earlier telogen formation. Alterecl 
acta derm atovenerologica A.P.A. Vol 8, 99, No 3 ---------- --- - - - - --- - - --- ----- 85 
Psoriasis oj the nails and scalp 
keratinization of the follicles and mechanic damage due 
to scales, which could stop the hair growth, may also 
play a role in the pathogenesis of telogen effluvium in 
scalp psoriasis ( 4). Scalp psoriasis may provoke scarring 
alopecia in rare cases. The hair density is drastically 
reduced in affected scalp areas producing a permanent 
alopecia (6, 7). 
In patients with psoriatic alopecias we have obser-
ved the fo llowing histopathological findings: 
Parakeratosis with micro-abscesses of neutrophils 
in the horny layer, absence of granular layer, psoriasi-
form epidermal hyperplasia, and papillomatosis . Horny 
plugs in some follicle infundibula are present. Seba-
ceous glands are atrophic or absent. Atrophic sebaceous 
glands resemble mantle-like structures (Fig. 2). A mode-
rately dense lymphocytic superficial perivascular infil-
trate, slight edema and dilated blood vessels within the 
papilla1y dermis and around the infundibulum and 
isthmus are detected. 
In vertical sections, an increased rate of catagen 
foll icles may be present. The histological findings of 
psoriatic scarring alopecia show a complete absence of 
follicular units, replaced by fibrosis. The epidermis is 
thin and no inflammatory infiltrates are observed (S). 
Figure 2. Mantle-like structures {H&E, 120x) 
86 
Figure 1. Scalp psoriasis 
Nail psoriasis 
Signs of nail psoriasis depend on the localization of 
the disease in the nail unit (9, 10). A number of nail 
abnormalities often occur simultaneously due to invol-
vement of different nail constituents in the same patients 
(9). Psoriasis affects fingernails more frequently than 
toenails. Psoriasis of ali 20 nails is rare . The clinical 
manifestations of fingernail psoriasis are, in order of 
freq uency: pitting, reddish oil (salmon) patches, ony-
Figure 3. Nail psoriasis: pitting, onycholysis and 
oil red atches 
R eview 
acta dermatovenerologica A.P.A. Vol 8, 99, No 3 
Review 
4 
Psoriasis of the nails and scalp 
Figure 4. Cluster of parakeratotic cells and a pit 
in the distal nail plate (H&E, 35x). 
cholysis (Fig. 3), subungual hyperkeratosis and splinter 
haemorrhages. Toenail psoriasis is usually characterized 
by monomorphous clinical signs and it consists of sub-
ungual hyperkeratosis and diffuse yellow-brown dis-
coloration of the nail plate. 
Pitting consists of punctate depressions (pits) of nail 
plate surface. Pits are deep, large and irregular and ran-
domly disu·ibuted. Defective keratinization of the pro-
ximal nail matrix produces the persistence of clusters 
of parakeratotic cells within the upper layers of the nail 
plate. Histopathologically, pits represent desquamation 
of parakeratotic cells in the superficial nail (Fig. 4) . Pits 
are rarely found in toenails. Differential diagnosis mostly 
includes pits of alopecia areata that are, however, sy-
mmetrically distributed in a regular pattern along the 
nail plate. 
Salmon patches and onycholysis are due to invol-
vement of the nail bed and are often associated (9, 10, 
11). 
Salmon patches are yellowish or salmon pink areas, 
irregular in size and shape visible through the trans-
parent nail plate. This sign is typical of psoriasis. 
Onycholysis represents the <listal or lateral detach-
ment of the nail plate from the nail bed. Histopatho-
logically, it is characterized by parakeratosis of the nail 
bed horny layer (12). Onycholysis is whitish because 
of the penetration of air under the detached nail p late. 
In psoriasis, the onycholytic area is typically surrounded 
by an erythematous border. 
Subungual hyperkeratosis describes the accu-
mulation of parakeratotic cells under the distal portion 
of the nail p late and hyponychium. In fingerna ils , 
parakeratotic cells often lose their cohesion and are 
progressively eliminated resulting in the development 
of onycholysis. In toenails, hyperkeratosis is usually 
tightly adherent to the nail plate, which becomes hard, 
thick and lifted up. Nail abnormalities seen in psoriasis 
and onychomycosis may be indistinguishable since sub-
ungual hyperkeratosis, onycholysis and splinter hae-
morrhages are clinical signs of both these conditions. 
Dermatophytes or other fungi can colonize psoriatic 
nails. Therefore a positive culture does not rule out 
Figure 5. Pustular psoriasis. 
Figure 6. Pustula with massive edema and 
spongiosis in the nail bed (H&E, 120x). 
acta dermatovenerologica A.P.A. Vol 8, 99, No 3 ---------- ------ ------ ---------- 87 
Psnriasis of the nails and scalp 
psoriasis, which could promote growth of fungi into 
the nails (1 3). 
shows pustules with massive edema, spongiosis of the 
nail bed (Fig. 6) and yellow brown scales and crust in 
the nail plate . Development of recurrent pustular lesions 
in the nail matrix area is not common and results in 
onychomadesis. Scarring of the involved nail matrix with 
partial or to tal loss of the nail plate is rare. 
Pustu/ar psoriasis frequently affects the nail unit. 
Nail involvement can occur in palmoplantar pustular 
psoriasis as well as in Hallopeau's acrodermatitis in 
which, usuall y, only one digit (most commonly a finger) 
is affected . In pustular psoriasis painful pustular lesions 
develop in the soft periungual tissues as well as in the 
nail bed and are associated w ith severe inflammation 
(Fig. 5) (14). 
Longstanding lesions produce a definitive atrophy 
ofthe nail apparatus and periungual soft tissues (9, 11) . 
Nail psoriasis has an unpredictable course. It often 
gets worse during the summer. Stressful events may 
precipitate relapses . In most cases the disease is chronic 
and complete remissions are uncommon (9) . In histop athological sections, pustular psoriasis 
C ES 
AUTHORS' 
ADDRESSES 
l. Dawber R, De Berkerd PR. Diseases of the scalp and skin diseases involving the scalp. In: Dawber R. 
Diseases of the hair and scalp. Oxford. Blackwell Science. 1997: 494-527. 
2. Orfanos CE, Frost PH. Seborrhoeic dermatitis, scalp psoriasis and hair. In: Orfanos CE, Happle R 
(eds). Hair and hair diseases. Berlin. Springer. 1990: 641-61. 
3. Shuster S. Psoriatic alopecia:Br J Dermatol 1972; 87: 73-7. 
4. Schoorl WJ, Van Baar HJ, Van de Kerkhof PCM. The hair root pattern in psoriasis of the scalp. Acta 
Derm Venereol (Stockh) 1992; 72: 141-2. 
5. Runne U, Kroneisen-Wiersma P. Psoriatic alopecia: acute and chronic hair loss in 47 patients with 
scalp psoriasis. Dermatology 1992; 185: 82-7. 
6. Wright AL, Messenger AG. Scarring alopecia in psoriasis. Acta Derm Venereol (Stockh) 1990; 70: 156-9. 
7. Kretzschmar L, Bonsmann G, Metze D, Luger TA, Schwarz T. Scarring psoriatic alopecia. Hautarzt 
1995; 46: 154-7. 
8. Bardazzi F, Fanti PA, Orlandi C, Chieregato C, Misciali C. Psoriatic scarring alopecia. Observations in 
four patients. Int J Dermatol. 1999; in press. 
9. Tosti A, Morelli R, Bardazzi F, Piraccini BM. Psoriasi ungueale. In: Dubertret L. Psoriasi. ISED; Brescia; 
1993: 201-7. 
10. Zaias N. Psoriasis of the nail. A clinical-pathological study. Arch Derm 1969; 99: 567-79. 
11. Zaias N. Psoriasis of the nail. In: Zaias N. The nail in health and disease. MTP. Lancaster. England. 
1980: 151-62. 
12. Robbins TO, Kouskoukis CE, Ackerman AB. Onycholysis in psoriatic nails. Am J Dermatopathol 
1983; 5: 39-41. 
13. Gupta AK, Lynde CW, Jain HC, Sibbald RG, Elewski BE, Daniel CR 3rd, Watteel GN, Summerbell RC. A 
higher prevalence of onychomycosis in psoriatics compared with non-psoriatics: a multicentre study. Br 
J Dermatol 1997; 136: 786-9. 
14. Burden AD , Kemmet D. The spectrum of nail involvement in palmoplantar pustulosis. Br J Dermatol 
1996; 134: 1079-82. 
Cosimo Misciali, MD, Department oj Dermatology, University oj Bologna, 
ViaMassarenti 1, 40138 Bologna, Jtaly 
Bianca Maria Piraccini, MD, same address 
Antonella Tasti, MD, same address 
R ev i ew 
88 acta dermatovenerologica A.P.A. Vol 8, 99, No 3