A 11-year-old girl presented with complaints of mild itchy lesions over bilateral elbows and knees of 1 year duration. There was no history of lesions anywhere else on the body. No other complaints like difficulty in vision or palmoplantar involvement were present. There was no history of atopy. Or any significant family history. Cutaneous examination revealed multiple discrete, erythematous, grouped follicular hyperkeratotic papules with a spiny surfaces and nutmeg grater feel over bilateral elbows, extending slightly over the arms and over bilateral knee joints [Figure 1a and b]. Dermoscopy done with DE-300 polarizing digital dermaoscope (Firefly) having 20× magnification showed whitish follicular keratotic plugs with peripheral yellowish rings, perifollicular erythema, and hair shaft in the center [Figure 2]. Nails, and mucoase were normal. Koebnerization was absent. Skin biopsy from one of the lesions showed acanthosis with broad and short rete ridges, thick suprapapillary plate, focal hypergranulosis, alternating orthokeratosis and parakeratosis, broad follicular infundibulum filled with orthokeratotic plug with perifollicular moderate lymphoplasmacytic inflammatory infiltrates, and perivascular lymphoplasmacytic inflammatory infiltrates in the dermis [Figure 3]. Based on the history, examination, dermoscopy, and histopathological findings, this case was diagnosed as juvenile circumscribed pityriasis rubra pilaris (PRP).
Figure 1.
Multiple discrete, erythematous, grouped follicular hyperkeratotic papules over (a) Left elbow, (b) right knee
Figure 2.
Dermoscopy (DE 300 dermoscope (firefly) 20× magnification with polarized light) showingwhitish follicular keratotic plugs (black arrow) with a peripheral yellowish ring (blue arrow), perifollicular erythema (red arrow), and hair shaft in the center (white arrow)
Figure 3.
Histopathology showingacanthosis with broad and short rete ridges, thick suprapapillary plate, focal hypergranulosis, alternating orthokeratosis and parakeratosis, broad follicular infundibulum filled with orthokeratotic plug with perifollicularand perivascular lymphoplasmacytic inflammatory infiltrates in the dermis (H and E stain ×40)
PRP is a rare papulosquamous disorder of childhood, characterized by circumscribed follicular keratoses, branny scale, orange-red erythema, and palmoplantar keratoderma.
PRP was initially classified on the basis of age at onset, behavior, clinical appearance, and prognosis by Griffith in 1980, which continues to be the mainstay in practice for delineating the disease.[1] The exact etiology of PRP is unknown.
Juvenile circumscribed (type-iv) PRP is usually seen in the later part of the first decade of life and is characterized by the formation of well-circumscribed, erythemato-squamous plaques studded with follicular and/or non-follicular papules with prominent keratotic plugging. Lesions are usually confined to the elbows and knees and is marked by remissions and exacerbations. In atypical cases, PRP has to be differentiated from other conditions which can be a diagnostic challenge and a skin biopsy has to be performed for confirmation.
Dermoscopy is a non-invasive diagnostic tool that allows visualization of many morphologic features not visible to the naked eye especially vascular and pigmented structures, so it represents a link between macroscopic dermatology and pathology.
Dermoscopic features of PRP have been described only in two case-reports. A study conducted by Azim et al.[1] showed that most common dermoscopic findings of PRP are yellowish background, whitish keratotic plug, linear vessels either solely or mixed with dotted vessels, arranged mainly peripherally.
Histopathology of PRP is characteristic and shows alternating columns of orthokeratosis and parakeratosis both in vertical and horizontal directions, focal or confluent hypergranulosis, thick suprapapillary plates, broad rete ridges, narrow dermal papillae, and sparse perivascular lymphocytic infiltrate. Plugging of follicular infundibulum by cornified cells is characteristic.
Few common follicular and non-follicular dermatoses, which must be considered in the differential diagnosis of PRP are tabulated with their clinical, dermoscopic, and histopathological differences in Table 1.
Table 1.
Differential diagnosis of juvenile circumscribed PRP
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