D3.256 - A Child with Mastocytosis presenting with generalized severe Pruritus: A Diagnostic Pitfall

Introduction:

Mastocytosis, a rare disorder characterized by pathological accumulation of mast cells and most commonly affecting the skin, is classified into cutaneous and systemic mastocytosis mostly with bone marrow involvement. Mast cells play a central role in immune responses and allergic reactions. In childhood, mastocytosis predominantly presents as cutaneous mastocytosis or solitary mastocytoma, often with spontaneous remission. However, persistence into adulthood or progression to systemic mastocytosis may occur. Cutaneous manifestations are characterized by Darier’s sign, a pathognomonic whealing and itching response to mechanical irritation. Especially in childhood, generalized skin lesions with blistering and severe pruritus exist. Systemic disease may present with hypotension, flushing, and anaphylaxis.

Case Presentation:Our female patient first developed flushing episodes during the third week of life, accompanied by cutaneous blistering, diarrhea, and vomiting. Serum tryptase was elevated at 29.5 µg/L (reference < 11.4 µg/L). Diffuse (plaque-type) cutaneous mastocytosis was diagnosed, and on-demand therapy with dimetindene  and oral prednisolone (0.5 mg/kg) was initiated. Clinical symptoms improved markedly, psychomotor development remained age appropriate and serum tryptase decreased to 11.55 µg/L.  At 10 years of age, the patient developed a severe flare lasting over one month, characterized by intense pruritus and increased whealing and scratching. Exacerbation was attributed to progression of mastocytosis and oral corticosteroids were used. However, the pruritus score increased during the next weeks up to 10 (NRS 0-10). Our examination revealed extensive scratching with bleeding and signs of self-induced skin pinching. Dermatological assessment including dermoscopy revealed a scabies infestation with mites and burrows on one foot. Following appropriate treatment, symptoms resolved rapidly and scratching behavior ceased.

Conclusion:Cutaneous mastocytosis is a rare condition presenting with skin lesions and itch attacks usually lasting 5-30 min after a trigger such as heat or mechanic irritation. As weeks-long, severe itch and extensive scratching with bleeding are not associated with this disease, other reasons for these symptoms should be considered.

This case highlights the importance of meticulous clinical reassessment even in patients with a confirmed rare diagnosis. Diagnostic anchoring should be avoided, and alternative or concomitant conditions must be considered to prevent patient suffering and ensure appropriate management.