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Hypopigmented mycosis fungoides in a 10-year-old boy

  • Author(s): Manzur, A
  • Zaidi, S T H
  • et al.
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Hypopigmented mycosis fungoides in a 10-year-old boy
A Manzur, S T H Zaidi
Dermatology Online Journal 12 (6): 21

Department of Dermatology. PAF Hospital Sargodha, Pakistan. aamirderm@hotmail.com

Abstract

Cutaneous T-cell lymphoma (CTCL) presenting with hypopigmented lesions is an uncommon clinical variant of the disease, usually described in dark-skinned patients. We report a case of hypopigmented CTCL in a 10-year-old boy. The disease has responded favorably to narrowband UVB therapy. This case illustrates the importance of clinical suspicion for mycosis fungoides in patients with widespread hypopigmentation.


Mycosis fungoides (MF) is the most common type of cutaneous T-cell lymphoma and is characterized by epidermotropic T lymphocytes that are clonally expanded in the skin. Mycosis fungoides has an estimated incidence of 0.4 per 100,000 persons [1]. Apart from the classic type of MF (patch, plaque, tumor) many atypical variants are reported, including psoriasiform, erythrodermic, follicular, noduloulcerative, ichthyosiform, poikilodermatous, morphea-like, and purpuric types [2]. The hypopigmented variety of MF is rarely reported and has mostly been encountered in dark-skinned people [3].


Clinical synopsis


Figure 1
Figure 1. Typical lesions of hypopigmented MF seen over the buttocks and trunk. Note the faint erythema in some lesions.

A 10-year-old Pakistani boy presented with a 3-month history of rapidly increasing hypopigmented patches over the body. He had mild to moderate pruritus. Previous treatments included topical corticosteroids and oral antihistamines. Physical examination showed widespread hypopigmented patches involving the face, trunk, and limbs. The buttocks were involved more than the other body areas. Individual lesions were a few mm to 4 cm, poorly defined, hypopigmented patches (Fig. 1). A few lesions showed slight superficial scaling and some had an erythematous component. There was no lymphadenopathy or hepatosplenomegaly. Laboratory investigations including complete blood count, liver function tests, renal function tests and urinalysis were normal. Abdominal ultrasonography and chest roentgenogram showed no abnormal findings.

A skin biopsy from the left arm showed an epidermotropic, atypical lymphoid infiltrate in the upper dermis, epidermal interface and epidermis. These lymphocytes had mild atypia with nuclear irregularity and hyperchromasia (Figs. 2 and 3). The lymphocytes were CD3 positive. Further immuno-phenotyping could not be done.


Figure 2Figure 2
Figure 2. Histopathology of a lesion showing epidermotropic mononuclear infiltrate.
Figure 3. The cellular atypia of the infiltrating lymphocytes is clearly evident on higher magnification.

The clinicopathological features were consistent with the diagnosis of MF stage IB (hypopigmented variety). Narrowband UVB (NB-UVB) therapy was started, 3 times a week on non-consecutive days. After 22 treatments, the disease has shown moderate improvement with 40 percent clearance of the lesions. He remains well 10 months after presentation.


Discussion

Less than 5 percent of cases of cutaneous T-cell lymphoma present in childhood, and most of these patients have either MF or lymphomatoid papulosis [4]. Mycosis fungoides presenting with hypopigmented lesions is an uncommon clinical variant of the disease, described mostly in dark-skinned or Asian patients [3]. Although MF is primarily a disease of adults and elderly patients, the hypopigmented variant is more common in children [5]. However, it should be emphasized that in dark-skinned individuals, hypopigmented MF is also an atypical manifestation, because most dark-skinned individuals with MF present with typical lesions [3]. In a recent study in Pakistan, 21.3 percent of the MF patients had the hypopigmented variety [2]. Hypopigmented lesions of MF can be present as the sole manifestation of the disease or can be associated with erythematous patches, plaques, or tumors [5].

The exact incidence of hypopigmented MF is still unknown and is probably underestimated [5]. This might be attributed to under-diagnosis of the condition, because the patients with hypopigmented MF are likely to remain undiagnosed or receive alternative diagnoses such as vitiligo, atopic dermatitis, chronic lichenoid dermatitis, or post-inflammatory hypopigmentation [6]. Other entities in the clinical differential diagnosis include pityriasis alba, tinea versicolor, leprosy, and post kala-azar dermal leishmaniasis. Indeed the latency period for the diagnosis of hypopigmented MF can be over 9 years [3]. The early diagnosis in our case is due to a high clinical suspicion for hypopigmented MF; it is not rare in our population.

The epidermal infiltrate in hypopigmented MF is reported to be predominantly of CD8-positive lymphocytes [7]. The pathogenesis of hypopigmentation is unclear. It might be because of destruction of melanocytes in affected skin by neoplastic and non-neoplastic T lymphocytes [5].

The predominant location on the buttocks and other unexposed body areas is an important feature and clue to the diagnosis [8]. Most of the reported cases of hypopigmented MF have stage-I disease; long-term survival of patients with this stage has been documented for both classical and hypopigmented MF [3]. Treatment of early-stage (IA, IB) MF includes topical corticosteroids, topical mechlorethamine, UVB, and PUVA [9]. Treatment with UVA-1 light has also been used successfully in a child to treat hypopigmented MF [10]. Recently, NB-UVB has also proved to be a safe and easily administered alternative therapy for early-stage MF. However, lower response rates have been seen in patients with higher Fitzpatrick skin phototype, possibly because of the photoprotective effect of melanin and also to the longer disease duration in these patients [11]. Our patient was of skin phototype V, but his disease duration was only 3 months. Therefore we anticipated a good response to NB-UVB therapy. In our case, the early diagnosis contrasts with most of the case series of hypopigmented MF in which the disease duration prior to diagnosis is in years [3, 11]. Long follow-ups have shown that hypopigmented MF responds well to PUVA, UVB, or topical mechlorethamine, resulting in remissions for years. Relapses that occur respond well to another course of therapy [3]. The long-term survival of patients with stage IA nonhypopigmented MF is similar to that of the uninvolved control population [12]; the same excellent prognosis has also been suggested for stage IA of hypopigmented MF [3].

The long-term outcome of the disease in this patient is yet to be seen. The basic intention of this report is to emphasize the fact that early diagnosis of hypopigmented MF is possible, provided physicians keep a high level of clinical suspicion. All clinicians should be aware of this peculiar manifestation of MF in younger patients. Patients with unusual hypopigmented lesions should always undergo a biopsy to rule out this rare variant of MF.

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