Ichthyosiform large plaque parapsoriasis: report of a rare entity.

Large plaque parapsoriasis (LPP) is an idiopathic, chronic scaly dermatosis classified within parapsoriasis group of diseases, occurring commonly in middle aged patients of all races and geographic regions. LPP and its variants are closely related to the patch stage of mycosis fungoides. The two types of LPP mostly described are the poikilodermatous and retiform parapsoriasis. We are reporting an ichthyosiform LPP for its rarity.

What was known?

Large plaque parapsoriasis is the early stage of mycosis fungoides or precursor of mycosis fungoides.

LPP is of two types, poikilodermatous and retiform types.

LPP occurs mainly in the fifth decade.

Introduction

LPP is an uncommon but not rare disorder, generally classified as poikilodermatous and retiform patterns according to clinical presentation.[1] LPP clinically presents as typically large, more than 5 cm, variably erythematous, round or irregularly shaped scaly patches or very thin plaque that are asymptomatic or mildly pruritic.[2] An atypical presentation with wide spread asymptomatic hypopigmented macule all over the body in a five year old child has been reported.[3] There is an unresolved controversy weather LPP is precursor of MF or early MF from the outset.[4] We hereby present a case of ichthyosiform LPP for its rarity.

Case Report

A 36 year old male patient presented to us with almost asymptomatic ichthyosiform lesions of three years’ duration which appeared gradually involving mostly the trunk and extremities. [Figures 1-3] At the time of reporting lesions also started appearing over the sides of the face. The lesions were ichthyosiform patches of varying sizes measuring five to ten centimeters in diameter, the borders of which merged with intervening normal skin. The dry adherent pigmented scales were of varying shapes and sizes with mild telangiectasia noted over few lesions. There was no anesthesia either over the lesions or peripherally in glove and stocking distribution. There was history of application of emollient and topical corticosteroids with neither any change in the morphology of the lesions nor their size. There was no history of systemic medication prior to or during the course of the disease. No abnormalities were detected in general survey and systemic examination including absence of lymphadenopathy. A provisional diagnosis of ichthyosiform MF was made. Routine investigations including complete hemogram, chest X-ray, Mantoux test were within normal limits as was his thyroid profile. Histopathological examination of biopsy specimen revealed mild hyperkeratosis with localized parakeratosis, irregular acanthosis and mild spongiosis. [Figure 4] Upper dermis contained dense lymphocytic infiltrate without any evidence of nuclear atypia or epidermotropism [Figure 5]. There was no granuloma formation. Immunohistochemical study of infiltrate expressed CD3, CD2, CD5 and CD4 but was negative for CD20, CD8, CD7 and CD30.

Figure 1

Scaly ichthyotic wrinkled plaques over back

Figure 3

Similar lesion over flexure aspect of lower limbs

Figure 4

Localized parakeratosis, mild acanthosis and focal dermal infiltrate (H and E, ×100)

Figure 5

Dense upper dermal lymphocytic infiltrate without epidermotropism (H and E, ×400)

Similar lesion over left flank and left upper extremity

The above findings prompted us to reconsider our diagnosis to ichthyosiform LPP. The patient was put on systemic phototherapy, but without any improvement even after three months of treatment.

Discussion

LPP can be regarded as the benign end of the MF disease spectrum and may progress to definite MF approximately 10% per decade[5] to 35% in some studies.[6] LPP tends to present in middle aged people with peak incidence in fifth decade with slight male preponderance.[2] Our patient had an early age of onset in the fourth decade. Lesions are usually persistent and favor non-sun exposed areas. Although the name suggests they actually present as patches rather than infiltrated plaques.[2] LPP lesions described are of mainly poikilodermatous and retiform types.[1] Our patient presented with patchy ichthyotic lesions over both exposed and non exposed parts without any sensory loss for last 3 years. He had no lymphadenopathy or organomegaly, or any features suggestive of disorders associated with acquired ichthyosis. Along with the clinical presentation the diagnosis of LPP should be supplemented by histopathological and immunohistochemical studies. Histology shows mild acanthosis, slight hyperkeratosis with spotty parakeratosis.[7] Immunohistological studies show similar features in LPP and early MF lesions including wide spread epidermal expression of HLA-DR, predominance of CD+ T cell subsets and frequent CD 7 antigen deficiency.[2] Histopathological examination in our patient showed acanthosis, hyperkeratosis and localized parakeratosis but did not reveal definite epidermotropism or Pautrier's microabscess or atypical lymphocytes in the basal layer of epidermis typically seen in MF.[7] Immunohistochemistry indicated T cell clonality. T cell receptor gene rearrangement study could not be done due to institutional non availability. The above findings neither rule out nor confirm the presence of either LPP or mycosis fungoides. Ichthyosiform MF has been described rarely.[8] Although our patient fulfilled the clinical criteria of “early diagnosis of MF” illustrated by the International Society of Cutaneous Lymphoma but histopathological criteria were not met.[9] Considering the absence of characteristic of immuno-pathological changes of MF in our case we preferred the diagnosis of ichthyosiform LPP. However, he needs continuous follow up and periodic evaluation for probable conversion to MF.

What is new?

Ichthyosiform pattern, of large plaque parapsoriasis.