Dermatology Online Journal

Generalized acanthosis nigricans in childhood
Vandana Mehta Rai MD DNB, C Balachandran MD
Dermatology Online Journal 12 (6): 14

Department of Skin and STD, Kasturba Medical College, Manipal, Karnataka. vandanamht@yahoo.com

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Abstract

Acanthosis nigricans in children is usually associated with obesity. Generalized acanthosis nigricans in childhood is rare. We report a 13-year-old boy with an 8-year history of generalized hyperpigmentation and velvety thickening of the skin. Despite an extensive physical and laboratory examination no evidence of underlying endocrinological or neoplastic disease was found.

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Acanthosis Nigricans (AN) is characterized by roughness and velvety thickening of the skin with hyperpigmentation. Acrochordons are commonly associated and predominantly affect the axillae, groins, submammary region, and back and sides of the neck. The condition may be inherited or may be associated with endocrine abnormality, obesity, use of drugs, or internal malignancy [1, 2]. The vast majority of AN cases in childhood are a benign hereditary form or a form related to insulin resistance. Generalized AN is extremely rare in childhood.

Clinical synopsis

A 13-year-old boy presented with complaints of generalized hyperpigmentation and corrugated skin of 8-years duration. History revealed that the initial signs of the disease commenced at the age of 5 years with hyperpigmentation around the neck. This gradually spread to involve the trunk, axillae, groins, and antecubital and popliteal fossae. The skin of the above areas also became thickened and rugose. The pigmentation soon spread to involve the face and trunk. At the same time the patient noticed multiple skin-colored, pedunculated lesions in the axillae, groin folds and the neck. The boy was born of a non-consanguineous marriage and had experienced normal growth and developmental milestones. There was no history of skin lesions at birth. He denied itching, unusual weight gain, or weight loss. There was no history of polyuria, polydypsia, or loss of appetite. There was no history of any motor, skeletal, or neurological deficit. There was no history suggestive of any ichthyotic disorder in the family. Cutaneous examination revealed generalized hyperpigmentation with thickening of skin which was accentuated in the axillae, groins, antecubital fossa, popliteal fossa, back and sides of the neck; multiple acrochordons were also present. The characteristic velvety plaque could be appreciated in the flexures. No hair, nail, or tooth abnormalities were noted; his mucous membranes, palms, and soles were normal.

Figure 1	Figure 2
Figure 1. Involvement of the axillae Figure 2. Generalized hyperpigmentation

Figure 3	Figure 4
Figure 3. Hyperpigmentation with thickened skin in the groin Figure 4. Hyperpigmented and corrugated skin on the neck with skin tags

Figure 5	Figure 6
Figure 5. Involvement of the back Figure 6. Involvement of the face

Figure 7
Figure 7. Involvement of the palms and soles

All routine hematological and biochemical parameters including an extensive endocrinological examination were within normal limits. Blood count, serum T3, T4, TSH, insulin levels, calcium, phosphorous, complete lipid profile with cholesterol, triglycerides, LDL, HDL, complete liver and renal profile, oral glucose tolerance test were all negative or within normal limits.

A skin biopsy specimen from the back showed marked hyperkeratosis with papillomatosis. There was no significant infiltrate in the dermis.

Based on the history and clinical examination a diagnosis of benign AN was considered. The diagnosis of epidermolytic hyperkeratosis was considered, but was excluded on the basis of negative history and histopathological findings. The patient was treated with oral vitamin A , topical retinoids, and keratolytics. After follow up for one year neither endocrinological nor malignant diseases have developed.

Discussion

AN has been classified into eight types [3, 4]:

• benign AN (an autosomal dominant trait)
• obesity associated AN (called as pseudoacanthosis nigricans)
• syndromic AN
• malignant AN
• unilateral AN
• acral AN
• drug induced AN (nicotinic acid, diethylstilbestrol)
• mixed AN (when 2 or more types of AN are present)

Generalized AN does not represent a specific type; it can be seen as a variant or rare manifestation of certain types of AN[5]. It is most commonly associated with internal malignancy in adults. The pathogenesis of AN remains unknown. One proposed mechanism is insulin resistance with reactive hyperinsulinemia [6]. Excess insulin binds to receptors on keratinocytes of fibroblasts leading to increased proliferation and growth of epidermal cells and thereby AN. Insulin resistance may be due to genetic abnormalities of insulin receptor or its function, obesity or autoimmune diseases associated with antibodies to insulin receptor. Malignancy-associated AN may be due to secretion of tumor products with insulin-like activity or of transforming growth factor which is thought to interact with the epidermal growth factor. The diagnosis of AN is usually straightforward given its characteristic clinical appearance with symmetrically distributed velvety hyperpigmented thickening of the skin most commonly seen in the flexures, palms, soles. Mucosae and genitalia may be affected. The separation between benign and malignant forms of the disease is important from the prognostic point of view. The treatment of AN is directed towards the underlying cause which may be either weight reduction, correction of endocrinological abnormality, discontinuation of offending drugs or the therapy of underlying malignancy. Therapies for idiopathic AN include emollients, keratolytics, topical and systemic retinoids. Generalized AN is rare and is most commonly seen in adults with an underlying malignancy. An extensive examination did not reveal evidence of underlying endocrine or malignant disease in our patient who remains under regular follow up.

References

1. Hurwitz S. Acanthosis nigricans. In: Hurwitz S,ed. Clinical Paediatric Dermatology,2nd ed. Philadelphia: WB Saunders,1993: 675-676

2. Levine N. Acanthosis nigricans. In: Schachner LA, Hansen RC, eds. Paediatric Dermatology, 1st ed. New York: Churchill Livingstone,1988: 1146-1150

3. Schwartz RA. Acanthosis nigricans. J Am Acad Dermatol1994;31:1-19

4. Schwartz Ra, Janniger CK. Childhood Acanthosis nigricans. Cutis 1995;55:337-341

5. Blume-Peytavi U, Speiker T, Reupke H,Orfanos CE. Generalised Acanthosis nigricans with vitiligo. Acta Derm Venereol 1996;76:377-380

6. Rendon MI,Cruz PD,Sontheimer RD, Berstresser PR. Acanthosis nigricans: a cutaneous marker of tissue resistance to insulin. J Am Acad Dermatol 1989;21:461-469.

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