Clinical Approach to MCAS Diagnosis and Cutaneous Mastocytosis
Cutaneous Matocytosis (CM)
CM is a subtype of mastocytosis where MC infiltration is limited to the skin. CM in children is usually a self-limited condition, and SM rarely occurs in childhood. Conversely, in adults, cutaneous lesions very commonly are a manifestation of SM [1].
Table 5: Features of Cutaneous Mastocytosis (CM) in Children vs Adults
Children | Adults | |
Average age at onset | < 2 years [27, 35-37] | 36 years [38] |
Associated with SM | - Rarely - Consider bone marrow biopsy if: | - Usually - BM bx in most cases, especially if tryptase > 20 |
- Hepatosplenomegaly, lymphadenopathy - Tryptase > 100 mg/dL or rising over time - Severe systemic symptoms - D816V mutation in peripheral blood | mg/dL, there is presence of systemic disease and/or MCA [1] | |
Maculopapular CM - Monomorphic - Polymorphic | 70-90% [27, 35, 36] - Less common [1] - More common [1] | Typical - More common [1] - Rare |
Mastocytoma | 10-35% [27, 35, 36] | Exceptionally rare |
Diffuse CM (DCM) | Rare (1-5%) [27, 35, 36] | Exceptionally rare |
D816V | 27-43% [27, 35, 36, 39] | 80-90% [4, 35, 36] |
Elevated serum tryptase | - Rare in CM and mastocytoma - Common in DCM [27] | |
Systemic symptoms (pruritus, flushing, GI) | 20-65%, especially in DCM [27, 35, 36] | Common |
Anaphylaxis | < 10% (usually in DCM) [35, 36, 40] | 50% [40] |
There are 3 forms of CM. The most common in both children and adults is maculopapular CM (MPCM, formerly called urticaria pigmentosa/UP), which is recognized clinically as tan lesions that become urticarial when scratched or stroked (Darier’s sign – upon stroking the lesion, the skin becomes red, swollen and itchy). Solitary mastocytomas are the second most common pediatric CM and can be associated with a site of trauma, such as at an immunization site, and are extremely rare in adults [41]. Diffuse CM (DCM) is the rarest form of CM, found in < 5% of pediatric CM and extremely seldom in adults [27, 35, 36]. It usually presents in early infancy, sometimes even at birth, with thickened skin, significant dermatographism, diffuse urticaria, and blistering/bullae. Degranulation of the MCs in DCM can lead to systemic symptoms, so minimizing trauma to the skin (including caution when eliciting Darier’s sign) is important.