Derm Dx: Multiple papules on the back since infancy

Excessive production of immune cells by the body leads to the accumulation of mast cells in the skin. This causes urticaria pigmentosa, which is a type of mastocytosis. Urticaria pigmentosa manifests as discrete brownish macules and papules on the skin....

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Excessive production of immune cells by the body leads to the accumulation of mast cells in the skin. This causes urticaria pigmentosa, which is a type of mastocytosis.

Urticaria pigmentosa manifests as discrete brownish macules and papules on the skin. Mast cells release mediators like histamine, which are highly inflammatory and irritating. Rubbing the macules will result in a wheal (hive). This is termed “Darier sign.”

The majority of patients develop urticaria pigmentosa early in their childhood, with fewer than 20% of cases having onset in adulthood. Childhood cases can begin as early as infancy.

The cutaneous lesions are commonly misidentified as insect bites, but will persist and spread symmetrically along the trunk. In some individuals, mast cell degranulation will cause pruritis and macules can become bullous.

In rare cases, systemic symptoms such as nausea, vomiting, tachycardia, and fainting can occur. These are largely attributed to the release of mast cell mediators. Symptoms typically resolve by adulthood, though residual pigmentation may persist in some individuals.

Adult-onset urticaria pigmentosa features similar physical manifestations as the childhood-onset form, but will involve more severe systemic symptoms. Reported symptoms include flushing, weight loss, gastrointestinal bleeding, and bone pain. Unlike the childhood-onset form, this disease type is typically chronic and will persist throughout the patient’s lifetime.

Telangiectasia macularis eruptiva perstans is a rare form of diffuse cutaneous mastocytosis found in less than 1% of mastocytosis patients. Macules appear on the trunk and limbs along with small, dilated blood vessels near the surface of the skin called telangiectasia. In contrast to the above disease forms, Darier sign is typically absent in telangiectasia macularis eruptive perstans.

Treatments of urticaria pigmentosa aim to ameliorate the symptoms of mastocytosis, but typically do not decrease the quantity of mast cells present. As a major product released by mast cells is histamine, antihistamines can be used to relieve symptoms of itching. Psoralen plus ultraviolet A (PUVA) phototherapy can target cutaneous macules by degranulating mast cells in a controlled manner.

Patient education is important, as substances that trigger of mast cell degranulation — nonsteroidal anti-inflammatory drugs, alcohol, narcotics — should be avoided to prevent exacerbation of the symptoms of urticaria pigmentosa.

Jiwem Li is a medical student at Baylor College of Medicine.
Adam Rees, MD, a graduate of the David Geffen School of Medicine at UCLA, practices dermatology in Los Angeles.