Congenital urticaria pigmentosa mistaken for non-accidental injury
Emma Porter MD, 1 Cynthia Heffron MD, PhD,2 Lesley Ann Murphy MD, 1 Cathal O’Connor MD 1, 3
  1. Dermatology, South Infirmary Victoria University Hospital, Cork, Ireland
  2. Pathology, Cork University Hospital, Cork, Ireland
  3. INFANT Research Centre, University College Cork, Cork, Ireland
Corresponding author: Cathal O’Connor, cathal.oconnor@ucc.ie
Word count: 492
Figure count: 2
References: 5
Conflict of interest: None
Consent statement: Written informed consent was obtained from the patient’s parents to publish this report in accordance with the journal’s patient consent policy.
A previously well male infant presented to his general practitioner (GP) for his routine 6-week check. His parents reported the presence of tan-brown lesions since birth. The marks were uniform in color, were present on the trunk, scalp, and face, and were not overlying bony prominences. The GP was concerned that these lesions represented bruising as a manifestation of NAI, and arranged urgent review at our pediatric department. Following assessment by the pediatric team he was admitted for investigation of potential NAI, and dermatology consultation was sought. On examination, scattered reddish brown to tan macules and papules were noted on the torso and limbs, not overlying bony prominences (Figure 1A, 1B). Darier sign was negative, although some reactive cutis marmorata was appreciable on the trunk following rubbing of multiple lesions. A diagnosis of urticaria pigmentosa (UP), or cutaneous mastocytosis, was made clinically. Skin biopsies demonstrated an infiltrate of spindled and round mast cells and scattered eosinophils within the superficial and mid dermis, with immunohistochemistry positive for CD117, consistent with UP (Figure 2A-2C). Blood tests during admission showed a normal complete blood count and coagulation screen (including von Willebrand factor), normal renal and liver function, normal lactate dehydrogenase, normal immunoglobulins, and normal mast cell tryptase. A cranial ultrasound and liver ultrasound were normal.
Mastocytosis is a spectrum of disease characterised by pathologic accumulation of mast cells in tissues, including skin, bone marrow and the gastrointestinal tract. The World Health Organisation has outlined three variants: cutaneous mastocytosis, systemic mastocytosis, and mast cell sarcoma. Cutaneous mastocytosis can be further classified as maculopapular cutaneous mastocytosis, also known as UP; diffuse cutaneous mastocytosis; and localised cutaneous mastocytomas.1 Paediatric cutaneous mastocytosis is regarded as a benign condition limited to skin, most commonly presenting as UP, which usually spontaneously regresses in puberty. 2 In contrast, adult-onset mastocytosis is more often associated with systemic involvement, a persistent course, and activating mutations of the KIT gene. 1
With UP, children typically present in the first two years of life with multiple reddish-brown macules, papules and/or plaques distributed anywhere on the body, most commonly the trunk. In darkly pigmented skin, lesions may be hyperpigmented and erythema less appreciable. Darier sign, a transient urticarial response upon gentle rubbing of the skin, is classic and supportive of diagnosis, though not always demonstrable. Treatment with antihistamines can be helpful. 3 UP has rarely been reported to be misdiagnosed as NAI. 4, 5Other ‘bruising’ mimics include disorders of coagulation, Valsalva petechiae, vasculitis, acute haemorrhagic edema, incontinentia pigmenti, phytophotodermatitis, coin rubbing, spooning, cupping, Mongolian spots, morphea, neuroblastoma, and ink stains, some of which may be unfamiliar to pediatricians or dermatologists.
Dermatologists have a crucial role in recognising cutaneous manifestations of NAI in children, which commonly includes bruising, particularly in infants who are not yet mobile. 4While consideration of NAI is important in all children presenting for medical care, this case highlights the importance of considering underlying dermatoses to avoid unwarranted distress and unnecessary investigations.