Prurigo Pigmentosa Is a Differential In Patients With Hyperpigmentation

VIENNA — Prurigo pigmentosa should be included in the differential diagnosis of hyperpigmentary disorders among patients worldwide, Dr. Hiroshi Shimizu reported at the 16th Congress of the European Academy of Dermatology and Venereology.

This condition, first described by Dr. Masaji Nagashima in 1971, is characterized by pruritic urticarial papules and papulovesicles arranged in a reticular pattern and distributed symmetrically on the back, neck, and chest. The lesions evolve over the course of several days, leaving behind distinctive pigmentation in a netlike, reticular-shaped pattern (J. Dermatol. 1978;5:61–7).

Dr. Shimizu was the first to report prurigo pigmentosa in the major English-language literature; he and his colleagues noted that nearly 100 cases had been seen in Japan but that the condition remained little known outside of that country (J. Am. Acad. Dermatol. 1985;12:165–9).

Approximately 700 cases have now been reported in Japan, and during recent years the condition has also been identified in patients of various races and from numerous countries, including the United Kingdom, Spain, Italy, Turkey, Iran, and Korea.

The majority of cases occur in young women, with more than 70% being seen among patients aged 11–20 years, said Dr. Shimizu, who is professor and chairman, department of dermatology, Hokkaido University School of Medicine, Sapporo, Japan.

Histopathologic findings depend on the stage of the lesion. In the early papular phase, numerous neutrophils can be seen in the epidermis, whereas in a fully developed lesion both neutrophils and lymphocytes are present, accompanied by spongiosis and vesiculation, he said. Histopathologic findings in the late pigmented lesion include a predominance of lymphocytes and melanophages and a lichenoid tissue reaction.

The differential diagnosis includes pigmented contact dermatitis, confluent and reticulated papillomatosis, leukocytoclastic vasculitis, and acute lupus erythematosus.

In Japan, the gold standard of treatment is minocycline or dapsone, both of which inhibit the migration and function of neutrophils. “Dapsone works somewhat more quickly than minocycline, but its recurrence rate is rather high,” Dr. Shimizu said. The usual starting dose of dapsone for adults is 50–75 mg/day, and for minocycline, 200 mg/day. “If one does not work, you can try the other, and if both do not work, your diagnosis may be wrong,” he said.

The etiology and pathogenesis of prurigo pigmentosa remain unknown, although some investigators have speculated on a possible metabolic influence because cases have been reported in patients with diabetes and in association with fasting, dieting, and ketosis (J. Am. Acad. Dermatol. 1996;34:509–11). “But we really don't know yet. I think an exogenous factor must be involved,” he said.

The condition involves pruritic urticarial papules and papulovesicles arranged in a reticular pattern. Courtesy Dr. Hiroshi Shimizu

VIENNA — Prurigo pigmentosa should be included in the differential diagnosis of hyperpigmentary disorders among patients worldwide, Dr. Hiroshi Shimizu reported at the 16th Congress of the European Academy of Dermatology and Venereology.

This condition, first described by Dr. Masaji Nagashima in 1971, is characterized by pruritic urticarial papules and papulovesicles arranged in a reticular pattern and distributed symmetrically on the back, neck, and chest. The lesions evolve over the course of several days, leaving behind distinctive pigmentation in a netlike, reticular-shaped pattern (J. Dermatol. 1978;5:61–7).

Dr. Shimizu was the first to report prurigo pigmentosa in the major English-language literature; he and his colleagues noted that nearly 100 cases had been seen in Japan but that the condition remained little known outside of that country (J. Am. Acad. Dermatol. 1985;12:165–9).

Approximately 700 cases have now been reported in Japan, and during recent years the condition has also been identified in patients of various races and from numerous countries, including the United Kingdom, Spain, Italy, Turkey, Iran, and Korea.

The majority of cases occur in young women, with more than 70% being seen among patients aged 11–20 years, said Dr. Shimizu, who is professor and chairman, department of dermatology, Hokkaido University School of Medicine, Sapporo, Japan.

Histopathologic findings depend on the stage of the lesion. In the early papular phase, numerous neutrophils can be seen in the epidermis, whereas in a fully developed lesion both neutrophils and lymphocytes are present, accompanied by spongiosis and vesiculation, he said. Histopathologic findings in the late pigmented lesion include a predominance of lymphocytes and melanophages and a lichenoid tissue reaction.

The differential diagnosis includes pigmented contact dermatitis, confluent and reticulated papillomatosis, leukocytoclastic vasculitis, and acute lupus erythematosus.

In Japan, the gold standard of treatment is minocycline or dapsone, both of which inhibit the migration and function of neutrophils. “Dapsone works somewhat more quickly than minocycline, but its recurrence rate is rather high,” Dr. Shimizu said. The usual starting dose of dapsone for adults is 50–75 mg/day, and for minocycline, 200 mg/day. “If one does not work, you can try the other, and if both do not work, your diagnosis may be wrong,” he said.

The etiology and pathogenesis of prurigo pigmentosa remain unknown, although some investigators have speculated on a possible metabolic influence because cases have been reported in patients with diabetes and in association with fasting, dieting, and ketosis (J. Am. Acad. Dermatol. 1996;34:509–11). “But we really don't know yet. I think an exogenous factor must be involved,” he said.

The condition involves pruritic urticarial papules and papulovesicles arranged in a reticular pattern. Courtesy Dr. Hiroshi Shimizu

VIENNA — Prurigo pigmentosa should be included in the differential diagnosis of hyperpigmentary disorders among patients worldwide, Dr. Hiroshi Shimizu reported at the 16th Congress of the European Academy of Dermatology and Venereology.

This condition, first described by Dr. Masaji Nagashima in 1971, is characterized by pruritic urticarial papules and papulovesicles arranged in a reticular pattern and distributed symmetrically on the back, neck, and chest. The lesions evolve over the course of several days, leaving behind distinctive pigmentation in a netlike, reticular-shaped pattern (J. Dermatol. 1978;5:61–7).

Dr. Shimizu was the first to report prurigo pigmentosa in the major English-language literature; he and his colleagues noted that nearly 100 cases had been seen in Japan but that the condition remained little known outside of that country (J. Am. Acad. Dermatol. 1985;12:165–9).

Approximately 700 cases have now been reported in Japan, and during recent years the condition has also been identified in patients of various races and from numerous countries, including the United Kingdom, Spain, Italy, Turkey, Iran, and Korea.

The majority of cases occur in young women, with more than 70% being seen among patients aged 11–20 years, said Dr. Shimizu, who is professor and chairman, department of dermatology, Hokkaido University School of Medicine, Sapporo, Japan.

Histopathologic findings depend on the stage of the lesion. In the early papular phase, numerous neutrophils can be seen in the epidermis, whereas in a fully developed lesion both neutrophils and lymphocytes are present, accompanied by spongiosis and vesiculation, he said. Histopathologic findings in the late pigmented lesion include a predominance of lymphocytes and melanophages and a lichenoid tissue reaction.

The differential diagnosis includes pigmented contact dermatitis, confluent and reticulated papillomatosis, leukocytoclastic vasculitis, and acute lupus erythematosus.

In Japan, the gold standard of treatment is minocycline or dapsone, both of which inhibit the migration and function of neutrophils. “Dapsone works somewhat more quickly than minocycline, but its recurrence rate is rather high,” Dr. Shimizu said. The usual starting dose of dapsone for adults is 50–75 mg/day, and for minocycline, 200 mg/day. “If one does not work, you can try the other, and if both do not work, your diagnosis may be wrong,” he said.

The etiology and pathogenesis of prurigo pigmentosa remain unknown, although some investigators have speculated on a possible metabolic influence because cases have been reported in patients with diabetes and in association with fasting, dieting, and ketosis (J. Am. Acad. Dermatol. 1996;34:509–11). “But we really don't know yet. I think an exogenous factor must be involved,” he said.

The condition involves pruritic urticarial papules and papulovesicles arranged in a reticular pattern. Courtesy Dr. Hiroshi Shimizu