On March 18, 2019, a 21-year-old male patient presented to our hospital with erythema, papules, and blisters all over the front chest and back for 10 months. Furthermore, dark red erythema with slight pruritus developed on the front chest and back with unknown etiology. The patient visited a local hospital and was diagnosed with pityrosporum folliculitis. He was treated externally with ketoconazole cream; however, the treatment effect was not good. In the past 3 months, the patient's skin lesions gradually spread to the neck and abdomen, and portions of the skin lesions were fused into pieces, which were not treated at that time. In the recent 1 month, several blisters accompanied by intense pruritus appeared on the erythematous areas of the front chest and back.
The patient denied a previous history of hypertension, diabetes, and other chronic diseases. Moreover, he denied a previous history of tuberculosis, hepatitis B, and other infectious diseases. Furthermore, previous histories of trauma and surgery as well as drug and food allergy were not reported. No similar diseases were reported in the family. The patient has been working for a long time as a fisherman. His diet mainly includes marine fish, shrimps, and other high-protein and high-fat diets, with low intakes of carbohydrates, including rice and noodles, fruits, and vegetables.
His neck, front chest, and back showed densely distributed round and oval edematous erythema. Portions of the erythematous areas had mung bean- to soybean-sized blisters. The blisters had tense walls and clear fluid, were easy to break, and had exudative and scabbed portions. He was Nikolsky sign negative (Figure 1A-D). 
His routine blood, urine, and stool examination as well as liver and kidney function examination were all not significantly abnormal. The results of antidouble-stranded DNA antibody, anti-BP180 antibody IgG, anti-BP230 antibody IgG, antidesmoglein 1 antibody IgG, antidesmoglein 3 antibody, antiepidermal basement membrane antibody IgG and IgA, and antispinous cell desmosomal antibody IgG and IgA examinations were negative. Additionally, polymerase chain reaction test results for herpes simplex virus types I and II were negative. Bacterial cultures of the blister fluid were negative.
Chest lesions (blisters) showed hyperkeratosis, and the skin lesions were intraepidermal blisters. The top of the blisters was composed of incomplete epidermis with scattered epidermal cells with poor keratosis. A large amount of serous fluid and low lymphocyte, neutrophil, and eosinophil levels were noted in the blisters. Additionally, a significant intracellular and intercellular edema in the lateral wall of the blisters was observed. Moderate infiltration of mixed inflammatory cells below the vesicle was observed. Immunofluorescence revealed negative test results for IgG, IgM, IgA, and C3; pemphigus and dermatitis herpetiformis were ruled out, and salt-split skin immunofluorescence was negative (Figure 2A and B). Subsequently, the patient was diagnosed with prurigo pigmentosa (PP). 
(1) the patient was instructed to have a reasonable diet by guiding him in increasing his daily intake of carbohydrates, including rice and noodles, fruits, and vegetables. (2) Normal saline was used to wash the erosive surface formed by the rupture of the blister, thereby removing the exudative fluid and necrotic tissue. (3) He was administered oral minocycline 100 mg twice daily. After 1 week, the pruritus was relieved, and the blisters dried up. After self-withdrawal from the medication, the patient resumed fishing, and the skin lesions recurred. He was subsequently administered oral minocycline 100 mg again twice daily. After 1 week, the blisters subsided, and the drug was discontinued after 1-month continuous oral administration. No symptom recurrence was noted during the follow-up visit.