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Discussion
Given the patient’s recent dietary changes, particularly his switch to a ketogenic diet, he was diagnosed with prurigo pigmentosa and treated with doxycycline, which cleared the rash. Prurigo pigmentosa is a rare inflammatory dermatosis characterized by net-like or reticulated pink, and later hyperpigmented, papules and plaques. Although the condition predominantly affects young women of East Asian descent, cases have been reported worldwide, highlighting the importance of considering this diagnosis in diverse populations, including children. Here, we describe a case of prurigo pigmentosa in a young male who had recently adopted a ketogenic diet for weight loss.
The association between prurigo pigmentosa and dietary changes, particularly ketosis, is becoming increasingly recognized. This condition is strongly linked to ketosis, a metabolic state marked by the production of ketone bodies (e.g., beta-hydroxybutyrate and acetoacetate) during carbohydrate restriction, fasting, or ketogenic diets, as seen in our patient. These ketone bodies may act as irritants or trigger oxidative stress and inflammatory cascades in the skin.
Ketoacidosis, particularly in prolonged or intense ketosis, is thought to alter the local skin microenvironment, promoting activation of inflammatory cytokines and immune cells. The ketogenic state is believed to generate oxidative stress through increased free fatty acid oxidation, leading to the production of reactive oxygen species (ROS). ROS can induce apoptosis of keratinocytes and inflammation in the epidermis, which is predominantly mediated by neutrophilic infiltration, as seen in histopathological findings. Elevated levels of pro-inflammatory cytokines, such as interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α), have been implicated in neutrophil recruitment and activation. IL-8 is particularly important for guiding neutrophils to areas of injury.
Secondary hyperpigmentation, a hallmark of this condition, is thought to result from melanin-laden macrophages and persistent melanocyte activation in response to inflammation at the dermo-epidermal junction.
The condition progresses in three stages. In the early stage, lesions appear as pruritic, urticarial plaques. These evolve into crusted erythematous papules and papulovesicles in the middle stage, as observed in our patient. Finally, in the late stage, the lesions mature into smooth, hyperpigmented plaques. Each stage of prurigo pigmentosa has distinct histopathological features.
Differential Diagnosis
The differential diagnosis for prurigo pigmentosa includes several conditions that may present similarly. Allergic contact dermatitis (ACD) can initially mimic the erythematous papules of prurigo pigmentosa, but the absence of a clear allergen exposure and failure to improve with avoidance measures makes ACD less likely. Psoriasis is another possibility, as its erythematous plaques may overlap with prurigo pigmentosa. However, the lack of silvery scales and chronicity makes psoriasis less likely in this case. Eczema, or atopic dermatitis, typically presents with pruritic, ill-defined plaques, often in flexural areas, which were not observed in this patient. Flagellate dermatitis, often caused by exposure to bleomycin or consumption of shiitake mushrooms, can present with linear erythematous lesions resembling prurigo pigmentosa. However, the absence of relevant exposures and a flagellate pattern in this patient rules out this diagnosis.
This case highlights the growing recognition of prurigo pigmentosa in the context of dietary trends, especially ketogenic diets, which have become popular for weight loss and other health benefits. Pediatric populations, in particular, may adopt such diets for various reasons and require careful monitoring, as their physiological responses may differ from those in adults. Prurigo pigmentosa has also been reported in a teenager girl with a history of anorexia nervosa, who was in a ketotic state.
Treatment options for prurigo pigmentosa include antibiotics such as minocycline or doxycycline, or macrolides for 4–10 weeks. Other treatment modalities include dapsone, Q-switch Nd:YAG laser, narrow-band ultraviolet B (UVB) phototherapy, and topical treatments like crisaborole and tacrolimus.
Early recognition of this condition is crucial to avoid unnecessary interventions and to allow for resolution through dietary modification. Dermatologists and pediatricians should maintain a high index of suspicion for prurigo pigmentosa in patients presenting with characteristic eruptions and a history of dietary ketosis.
Catalina Matiz is a pediatric dermatologist at Southern California Permanente Medical Group, San Diego.
Suggested Reading
1. Mufti A et al. Clinical Manifestations and Treatment Outcomes in Prurigo Pigmentosa (Nagashima Disease): A Systematic Review of the Literature. JAAD Int. 2021 Apr 10:3:79-87. doi: 10.1016/j.jdin.2021.03.003.
2. Yang J et al. Use of Minocycline for the Treatment of Prurigo Pigmentosa with Intraepidermal Vesiculation: A Case Report. J Int Med Res. 2021 May;49(5):3000605211015593. doi: 10.1177/03000605211015593.
3. Capucilli P et al. Prurigo Pigmentosa: An Itchy, Urticarial Eruption Confused for Food Allergy. J Allergy Clin Immunol Pract. 2018 Jul-Aug;6(4):1381-1382. doi: 10.1016/j.jaip.2018.02.033.
Discussion
Given the patient’s recent dietary changes, particularly his switch to a ketogenic diet, he was diagnosed with prurigo pigmentosa and treated with doxycycline, which cleared the rash. Prurigo pigmentosa is a rare inflammatory dermatosis characterized by net-like or reticulated pink, and later hyperpigmented, papules and plaques. Although the condition predominantly affects young women of East Asian descent, cases have been reported worldwide, highlighting the importance of considering this diagnosis in diverse populations, including children. Here, we describe a case of prurigo pigmentosa in a young male who had recently adopted a ketogenic diet for weight loss.
The association between prurigo pigmentosa and dietary changes, particularly ketosis, is becoming increasingly recognized. This condition is strongly linked to ketosis, a metabolic state marked by the production of ketone bodies (e.g., beta-hydroxybutyrate and acetoacetate) during carbohydrate restriction, fasting, or ketogenic diets, as seen in our patient. These ketone bodies may act as irritants or trigger oxidative stress and inflammatory cascades in the skin.
Ketoacidosis, particularly in prolonged or intense ketosis, is thought to alter the local skin microenvironment, promoting activation of inflammatory cytokines and immune cells. The ketogenic state is believed to generate oxidative stress through increased free fatty acid oxidation, leading to the production of reactive oxygen species (ROS). ROS can induce apoptosis of keratinocytes and inflammation in the epidermis, which is predominantly mediated by neutrophilic infiltration, as seen in histopathological findings. Elevated levels of pro-inflammatory cytokines, such as interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α), have been implicated in neutrophil recruitment and activation. IL-8 is particularly important for guiding neutrophils to areas of injury.
Secondary hyperpigmentation, a hallmark of this condition, is thought to result from melanin-laden macrophages and persistent melanocyte activation in response to inflammation at the dermo-epidermal junction.
The condition progresses in three stages. In the early stage, lesions appear as pruritic, urticarial plaques. These evolve into crusted erythematous papules and papulovesicles in the middle stage, as observed in our patient. Finally, in the late stage, the lesions mature into smooth, hyperpigmented plaques. Each stage of prurigo pigmentosa has distinct histopathological features.
Differential Diagnosis
The differential diagnosis for prurigo pigmentosa includes several conditions that may present similarly. Allergic contact dermatitis (ACD) can initially mimic the erythematous papules of prurigo pigmentosa, but the absence of a clear allergen exposure and failure to improve with avoidance measures makes ACD less likely. Psoriasis is another possibility, as its erythematous plaques may overlap with prurigo pigmentosa. However, the lack of silvery scales and chronicity makes psoriasis less likely in this case. Eczema, or atopic dermatitis, typically presents with pruritic, ill-defined plaques, often in flexural areas, which were not observed in this patient. Flagellate dermatitis, often caused by exposure to bleomycin or consumption of shiitake mushrooms, can present with linear erythematous lesions resembling prurigo pigmentosa. However, the absence of relevant exposures and a flagellate pattern in this patient rules out this diagnosis.
This case highlights the growing recognition of prurigo pigmentosa in the context of dietary trends, especially ketogenic diets, which have become popular for weight loss and other health benefits. Pediatric populations, in particular, may adopt such diets for various reasons and require careful monitoring, as their physiological responses may differ from those in adults. Prurigo pigmentosa has also been reported in a teenager girl with a history of anorexia nervosa, who was in a ketotic state.
Treatment options for prurigo pigmentosa include antibiotics such as minocycline or doxycycline, or macrolides for 4–10 weeks. Other treatment modalities include dapsone, Q-switch Nd:YAG laser, narrow-band ultraviolet B (UVB) phototherapy, and topical treatments like crisaborole and tacrolimus.
Early recognition of this condition is crucial to avoid unnecessary interventions and to allow for resolution through dietary modification. Dermatologists and pediatricians should maintain a high index of suspicion for prurigo pigmentosa in patients presenting with characteristic eruptions and a history of dietary ketosis.
Catalina Matiz is a pediatric dermatologist at Southern California Permanente Medical Group, San Diego.
Suggested Reading
1. Mufti A et al. Clinical Manifestations and Treatment Outcomes in Prurigo Pigmentosa (Nagashima Disease): A Systematic Review of the Literature. JAAD Int. 2021 Apr 10:3:79-87. doi: 10.1016/j.jdin.2021.03.003.
2. Yang J et al. Use of Minocycline for the Treatment of Prurigo Pigmentosa with Intraepidermal Vesiculation: A Case Report. J Int Med Res. 2021 May;49(5):3000605211015593. doi: 10.1177/03000605211015593.
3. Capucilli P et al. Prurigo Pigmentosa: An Itchy, Urticarial Eruption Confused for Food Allergy. J Allergy Clin Immunol Pract. 2018 Jul-Aug;6(4):1381-1382. doi: 10.1016/j.jaip.2018.02.033.
Discussion
Given the patient’s recent dietary changes, particularly his switch to a ketogenic diet, he was diagnosed with prurigo pigmentosa and treated with doxycycline, which cleared the rash. Prurigo pigmentosa is a rare inflammatory dermatosis characterized by net-like or reticulated pink, and later hyperpigmented, papules and plaques. Although the condition predominantly affects young women of East Asian descent, cases have been reported worldwide, highlighting the importance of considering this diagnosis in diverse populations, including children. Here, we describe a case of prurigo pigmentosa in a young male who had recently adopted a ketogenic diet for weight loss.
The association between prurigo pigmentosa and dietary changes, particularly ketosis, is becoming increasingly recognized. This condition is strongly linked to ketosis, a metabolic state marked by the production of ketone bodies (e.g., beta-hydroxybutyrate and acetoacetate) during carbohydrate restriction, fasting, or ketogenic diets, as seen in our patient. These ketone bodies may act as irritants or trigger oxidative stress and inflammatory cascades in the skin.
Ketoacidosis, particularly in prolonged or intense ketosis, is thought to alter the local skin microenvironment, promoting activation of inflammatory cytokines and immune cells. The ketogenic state is believed to generate oxidative stress through increased free fatty acid oxidation, leading to the production of reactive oxygen species (ROS). ROS can induce apoptosis of keratinocytes and inflammation in the epidermis, which is predominantly mediated by neutrophilic infiltration, as seen in histopathological findings. Elevated levels of pro-inflammatory cytokines, such as interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α), have been implicated in neutrophil recruitment and activation. IL-8 is particularly important for guiding neutrophils to areas of injury.
Secondary hyperpigmentation, a hallmark of this condition, is thought to result from melanin-laden macrophages and persistent melanocyte activation in response to inflammation at the dermo-epidermal junction.
The condition progresses in three stages. In the early stage, lesions appear as pruritic, urticarial plaques. These evolve into crusted erythematous papules and papulovesicles in the middle stage, as observed in our patient. Finally, in the late stage, the lesions mature into smooth, hyperpigmented plaques. Each stage of prurigo pigmentosa has distinct histopathological features.
Differential Diagnosis
The differential diagnosis for prurigo pigmentosa includes several conditions that may present similarly. Allergic contact dermatitis (ACD) can initially mimic the erythematous papules of prurigo pigmentosa, but the absence of a clear allergen exposure and failure to improve with avoidance measures makes ACD less likely. Psoriasis is another possibility, as its erythematous plaques may overlap with prurigo pigmentosa. However, the lack of silvery scales and chronicity makes psoriasis less likely in this case. Eczema, or atopic dermatitis, typically presents with pruritic, ill-defined plaques, often in flexural areas, which were not observed in this patient. Flagellate dermatitis, often caused by exposure to bleomycin or consumption of shiitake mushrooms, can present with linear erythematous lesions resembling prurigo pigmentosa. However, the absence of relevant exposures and a flagellate pattern in this patient rules out this diagnosis.
This case highlights the growing recognition of prurigo pigmentosa in the context of dietary trends, especially ketogenic diets, which have become popular for weight loss and other health benefits. Pediatric populations, in particular, may adopt such diets for various reasons and require careful monitoring, as their physiological responses may differ from those in adults. Prurigo pigmentosa has also been reported in a teenager girl with a history of anorexia nervosa, who was in a ketotic state.
Treatment options for prurigo pigmentosa include antibiotics such as minocycline or doxycycline, or macrolides for 4–10 weeks. Other treatment modalities include dapsone, Q-switch Nd:YAG laser, narrow-band ultraviolet B (UVB) phototherapy, and topical treatments like crisaborole and tacrolimus.
Early recognition of this condition is crucial to avoid unnecessary interventions and to allow for resolution through dietary modification. Dermatologists and pediatricians should maintain a high index of suspicion for prurigo pigmentosa in patients presenting with characteristic eruptions and a history of dietary ketosis.
Catalina Matiz is a pediatric dermatologist at Southern California Permanente Medical Group, San Diego.
Suggested Reading
1. Mufti A et al. Clinical Manifestations and Treatment Outcomes in Prurigo Pigmentosa (Nagashima Disease): A Systematic Review of the Literature. JAAD Int. 2021 Apr 10:3:79-87. doi: 10.1016/j.jdin.2021.03.003.
2. Yang J et al. Use of Minocycline for the Treatment of Prurigo Pigmentosa with Intraepidermal Vesiculation: A Case Report. J Int Med Res. 2021 May;49(5):3000605211015593. doi: 10.1177/03000605211015593.
3. Capucilli P et al. Prurigo Pigmentosa: An Itchy, Urticarial Eruption Confused for Food Allergy. J Allergy Clin Immunol Pract. 2018 Jul-Aug;6(4):1381-1382. doi: 10.1016/j.jaip.2018.02.033.
Case Report
A 16-year-old Hispanic male with a history of hyperlipidemia presents to his pediatrician's office for a routine well-child check-up. He reports a pruritic rash on his neck and chest that has been present for the past 1.5 weeks. The rash is itchy, and although a cream from Mexico initially helped, it has not been effective recently. The patient mentions that he has increased his gym workouts and has been training for basketball. He has a history of obesity but has lost almost 100 pounds in the last 6 months. Most recently, he has stopped consuming carbohydrates and has been fasting in the mornings.
There is no history of eczema or psoriasis, either in the patient or his family.
Physical Examination
The patient weighs 147 pounds, a significant decrease from his previous weight of 270 pounds 6 months ago. Other vital signs are within normal limits.
On physical examination, the patient presents with net-like, pink, scaly plaques on his neck, with no other rashes on the body (see Pictures 1 and 2).