Finger nail pitting in psoriasis and its relation with different variables.

Incidence of pitting, vary considerably in different types of psoriasis. In clinical practice, toe nail examination is inconvenient. There are inadequate studies which show relation of nail pitting with duration and severity of the disease. The objective was to examine the incidence of finger nail pitting in all types of cutaneous psoriasis and its relation with different variables. This is a clinico-epidemiological study. A careful clinical examination of finger nails was done in day time. Severity of disease was calculated by psoriasis area severity index (PASI). Statistical analysis was done using Microcomputer statistics software (MSTAT). In study group, 621 patients and in control group 350 people were taken. Finger nail pitting was present in 37% (total number was < 20 in 17%; 20-60 in 8% and > 60 in 12%) in study group. In control group, it was present in 10% (in all cases total number was < 20). In < 1 year duration group, pitting was present in 32% of cases, while in > 1 year duration group it was 40.5%. In mild psoriasis, pitting was present in 34.2%, while in severe cases it was 47.6%. Finger nail pitting is an important nail finding in psoriasis and its incidence increases with duration and severity of disease.

What was known?

Pitting is a common feature of psoriasis. Its relation with severity and duration of the disease is not known.

Introduction

Nail pitting is a well-known nail change in psoriasis. It is more common in arthritic type of psoriasis.[12] Figures for its incidence vary considerably. Nail pitting may occur in apparently normal subjects. Nail changes are present in 25-50% of all cases.[3] There is no sex predilection, but patients over 40 years are affected twice as often as those under 20 years.[45] But the data regarding relationship between nail pitting with total duration of disease and disease severity are not known in best of my knowledge. Though pitting is the most frequent change seen;[45] discoloration, subungual hyperkeratosis and onycholysis are common. Nail changes, especially nail pitting may give an important clue for the diagnosis of psoriasis and its differentiation from other similar dermatological condition. The aim of this study was to find the incidence of nail pitting in different types of cutaneous psoriasis and its relation to different variables (like duration and severity of the disease) in an outdoor clinic.

Materials and Methods

A case control study comprised of 621 psoriatic patients in study group and 350 non-psoriatic cases in control group were recruited consecutively from skin outpatient clinic of a tertiary health care system, J. N. Medical College Hospital, A. M. U., Aligarh. Patients were from Indo-Aryan Ethnic group. This is a clinico-epidemiological study. All types (except isolated nail and arthritic psoriasis) and all grades of psoriasis were included. Exclusion criteria were other concomitant dermatological or medical disorders, such as lichen planus, alopecia areata, vitiligo and other autoimmune disorder. Control group comprised of patient attendants, and patients with acne, impetigo, melasma, scabies, herpes simplex, milia etc., Diagnosis of the disease was done mainly on clinical grounds but histopatholocal examination was done in some cases to confirm the diagnosis and exclude other similar conditions. Potassium hydroxide examination was done in almost all cases to rule out fungal infection. Biopsy of nail was taken in those whose diagnosis of nail psoriasis was not sure from clinical appearance. Simple questionnaire was used. In cases of infants and children, history of total duration was taken from their parents. A careful examination of all finger nails was done in all cases in day light.

Pitting was divided in three groups: Less than 20; 20-60; and more than 60. Disease severity was calculated by using psoriasis area severity index (PASI). Patient with PASI of 10 was kept in mild psoriasis, more than 10 as a severe psoriasis. Duration of disease was divided into two groups: Less than 1 year and more than 1 year.

Statistical analysis was done with the help of MSTAT. P value of < 0.05 was taken as significant and a value of < 0.001 as highly significant.

Results

A total of 621 psoriatic patients were included in study group and in control group 350 cases were taken. In study group, 430 (69.2%) patients were males and 191 (30.8%) females. Majority of patients were having chronic plaque type of psoriasis (65.5%) followed by palmo-planter psoriasis. Patient characteristics are given in Table 1. According to PASI, 469 cases (75.5%) were mild; 152 cases y (24.5%) were severe type. In study group, finger nail pitting was present in 37 percent of cases [Table 2], in which total number of nail pits were less than 20 in 17 percent; 20-60 in 8 percent; and more than 60 in 12 percent [Table 3]. In control group, nail pitting was present in 9.7 percent of cases and in all cases number of nail pits were less than 20. This difference in incidence is statistically significant (χ2= 83.04; P < 0.001). Total duration wise, 40.4% cases were in less than or 1 year of duration group; while 59.6% cases in more than one year duration group. Nail pitting was significantly high in more than 1 year group (χ2= 4.45; P < 0.05) [Table 4]. In mild psoriasis, pitting was present in 34.2% of cases; while in severe psoriasis it was in 47.6% of cases. Incidence of finger nail pitting increases with increase in severity of the disease and this difference is statistically significant (χ2= 7.89; P < 0.05) [Table 5].

Table 1

Patient characteristics

Table 2

Finger nail pitting: In study and control groups

Table 3

Number of nail pitting

Table 4

Relation between duration of the disease and nail pitting

Table 5

Relation between disease severity and nail pitting

Discussion

Nail changes are frequent in psoriasis. These changes are seen in association with all types of psoriasis of the skin and are frequently present with psoriatic arthropathy.[12] Changes in nail varies from minor defects in nail plate (pits) to severe alteration of nail organ (onychodystrophy) and loss of nail plate (pustular psoriasis of nail). These morphologic alterations reflect the extent to which the psoriatic process affects the various portions of the nail organ. Nail organ consists of proximal nail fold, nail matrix, nail bed and hyponychium. Localization of psoriatic tissue changes at these sites and duration of these processes decide the degree of nail involvement.

The proximal nail fold is a skin fold that consists of dorsal and a ventral portion. The dorsal portion is anatomically similar to the skin of the dorsum of the digit but thinner and devoid of pilosebaceous units. Pits are apparently due to disturbance in maturation and defective keratinization of the dorsal side of the proximal nail fold. Alkiewics[6] claims that the pits are due to the retention of nuclei in parts of the nail keratin; these areas, being weaker, are shed and the pits are form when the surface is lost.

Disease severity was classified according to PASI into mild and severe. The basis for putting patients with less than 10 PASI score in mild category is the facts that systemic drugs are usually used when PASI is more than 10.

Pitting is well known nail deformity in psoriasis and probably the most frequent. The pits are usually quite small, about the size of a pin-head (under 1 mm in diameter), but much larger depressions, and even isolated punch-out areas, are seen occasionally. These are punctuating depressions in the nail, arranged in haphazard or regular patterns. Baran and Tosti considered nail pits as characteristic of psoriasis.[7] Nail pitting is not always due to psoriasis. A similar, although finer, pitting may be seen in alopecia areata. A coarser more irregular pitting is often seen in eczema or dermatitis. Sometimes pitting may be found in lichen planus, chronic paronychia and fungal infections. Rarely, uniform pitting of whole nail plate appears to be a developmental anomaly. A few isolated small pits may be present without other evidence of skin disease.

Pits may vary in frequency from small, irregularly spaced depressions on the surface of the one or more nails to regular uniform pitting of all nails. De Berker et al. described that the presence of more than 20 finger nail pitting suggest a psoriatic cause of the nail dystrophy, more than 60 pits per person are unlikely to be found in the absence of psoriasis.[8] This was the basis for division of nail pits according to number. Less than 20 pits in all nails are non-specific and may be present in non-psoriatic conditions. More than 20 but less than 60 nail pits are suggestive of psoriasis and more than 60 pits are supposed to be diagnosis of psoriasis. In this present study, total number of pits in all finger nails in control group was less than 20. None of non-psoriatic case had more than 20 nail pits. In fact, in majority of non-psoriatic cases in control group, nail pitting was less than 10 in number. This study further strengthens the concept of more than 20 nail pits to be a feature of psoriasis. Incidences of nail changes vary considerably in psoriasis. Taggart and Wright found nail involvement in 31% of cases with the isolated cutaneous form of psoriasis[9] and Zaias found it to be 25-50% of cases.[3] These findings are comparable with the results of the present study. Farber and Nall reported that finger nails are involved in 50 percent of subjects and toe nails in 35 percent.[6] I had chosen only finger nails because in my first hundred psoriatic patients, toe nail pitting was present in only three cases and in all those cases total number was less than ten. Taggart and Wright found nail pitting exclusively in finger nails.[9] De Berker et al. described pitting in finger nail only.[8] These studies provided some clues for choosing finger nail only. In clinical practice, toe nail examination is inconvenient. Among all nail changes, I chose incidence of nail pitting only because, this is a minor defect in nail and in majority of cases patients did not notice the change and in some cases Dermatologists forget or missed nail pitting during clinical examination. Nail pitting may give an important supporting clue for clinical diagnosis of psoriasis in some early or suspected cases especially when more than 20 in number.

Studies regarding relationship between nail pitting and severity of the disease and duration of the disease are not known in best of my knowledge. This current study showed the relationship between these variables. Results of this study strongly indicate the relationship. Incidence of nail pitting is more in severe form of the disease.

What is new?

Incidence of finger nail pitting increases with increase in total duration and severity of the disease.